(opyright 1993 by The Jouriial of Bone atti Joi,,t S,trgerc, Incorporated

Current Concepts Review

Injuries of the Posterior Cruciate Ligament

BY COMMANDER D. C. COVEY*. MEDICAL CORPS. UNITED STATES NAVAL RESERVE.
AND ALEXANDER A. SAPEGA, M.D.t. BREMERTON. WASHINGTON

Investigation performed at the Department of Orthopaedic Surger.v, Naval Hospital, Brenierton

Although the anterior cruciate ligament has re- with extension, while the posterior-fiber group, which
ceived much attention in the orthopaedic literature, the has a much smaller cross-sectional area, is lax with
posterior cruciate ligament has not attracted similar flexion and tightens with extension394953”. In a recent
interest. With the exception of avulsion fractures’5, in- study of the functional anatomy of the posterior cruciate
juries of the posterior cruciate ligament have almost ligament, O’Brien et al.”’ also described the ligament in
universally been treated non-operatively in the gen- terms of two fiber bundles: a posterior-oblique bundle,
eral orthopaedic community, which has left this prob- consisting of a small (approximately 5 per cent of the
lem outside the mainstream of operative orthopaedics. substance of the ligament) but distinctly recognizable
Recent studies, however, have shed new light on the group of fibers that run obliquely across the posterior
natural history of injury to the posterior cruciate liga- surface of the ligament, originating at the posterosu-
ment, as well as on its complex anatomy and functional perior aspect of the femoral attachment and inserting
mechanical behavior. The new information is likely to posterolaterally on the tibia; and an anterior bundle,
alter the way that orthopaedic surgeons have tradition- representing the remaining 95 per cent of the ligament.
ally treated injuries to this structure. Characterization of the macroscopic anatomy of the
posterior cruciate ligament as comprised of only two
Anatomy
reciprocally functioning parts is perhaps too simplistic.
Morphology Kurosawa et al.” and Trent et al.”7 believed that the
The posterior cruciate ligament is surrounded by a ligament is best described in terms of anterior, middle,
synovial sleeve. The ligament has an average length of and posterior fiber bundles according to the location of
thirty-eight millimeters and an average width of thirteen the femoral insertion. Recent studies of the macroscopic
millimeters, and the cross-sectional area decreases from and functional anatomy have characterized the ligament
the proximal to the distal attachments”45. In about 70 per as a continuum of fibers without truly separate bands or
cent of knees, there is either an anterior meniscofemoral bundles23”. In order for surgeons to understand the com-
ligament of Humphrey or a posterior meniscofemoral plex anatomy of this continuum of fibers, an anatomical
ligament of Wrisberg: the latter is more common and is subdivision scheme, consisting of so-called fiber-regions,
characterized by a femoral origin merging with that of has been proposed on the basis of functional as well as
the posterior cruciate ligament3”47. These meniscofem- morphological criteria23. The four consistent geographi-
oral ligaments may play a minor role as secondary re- cal fiber-regions (as opposed to separate bands) have
straints to posterior tibial translation after complete been called anterior, central, posterior longitudinal, and
transection of the posterior cruciate ligament2”. posterior oblique, mainly on the basis of the orientation
Traditionally, the posterior cruciate ligament has of the fibers, the mechanical behavior during motion of
been described as consisting of two parts, or so-called the joint, and the osseous sites of insertion23. Most of the
bands, variously called anterior or anterolateral and substance of the posterior cruciate ligament is made up
posterior or posteromedials349w. A number of au- of the anterior and central fiber-regions, with the com-
thors have noted that the large cross-sectional anterior- bined posterior-longitudinal and posterior-oblique fi-
fiber group tightens with flexion of the knee and relaxes bers accounting for only 10 to 15 per cent of the mass
of the ligament23 (Fig. 1).
*Department of Orthopaedic Surgery. Naval Hospital, Boone
Road. Bremerton, Washington 98312-1898. Please address requests
Blood Supply
for reprints to Commander Covey.
The middle genicular artery, a branch of the poplit-
tSports Medicine Center. Weightman Hall. University of Penn-
sylvania School of Medicine. 235 South 33rd Street, Philadelphia. eal artery, provides a major contribution to the blood
Pennsylvania 19104-6397. supply of the posterior cruciate ligament”. It also sup-

1376 THE JOURNAL OF BONE AND JOINT SURGERY

 INJURIES OF THE POSTERIOR CRUCIATE LIGAMENT 1377

ANATOMIC SCHEME
OF
PCL FIBER-REGIONS”
AND THEIR
OSSEOUS
INSERTION SITES

Posterior Longitudinal Posterior Oblique

FIG. 1

Anatomical schematic drawings showing the four fiber-regions of the posterior cruciate ligament (PCL) and their osseous sites of
attachment on the medial femoral condyle and the posterior part of the tibia.

plies vessels to the ligament’s synovial sheath, which turator nerve”’. Kennedy et al.”’ observed superficial
itself is a major contributor to the blood supply295. subsynovial axons in the posterior cruciate ligament as
The distal part of the ligament receives a portion of its well as Golgi-like tension receptors near its origin.
vascular supply from capsular vessels originating from Schultz et al.”' noted fusiform mechanoreceptor struc-
the inferior genicular and popliteal arteries”5. The poste- tures, which morphologically resembled Golgi tendon
nor cruciate ligament has been found to have a more organs, in anterior and posterior cruciate ligaments from
abundant vascular supply than the anterior cruciate osteoarthrotic knees. These receptor organs, thought to
ligament77. play a role in proprioceptive reflex arcs, were located on
the surface of the ligament in fibrous fatty and vascu-
Innervation lar tissue well beneath the synovial sheaths”. Katonis et
The posterior cruciate ligament and its synovial al.59, in a recent histological study of mechanorecep-
sleeve are supplied by nerve fibers from the popliteal tors in posterior cruciate ligaments from healthy knees,
plexus, which receives contributions from the posterior identified Ruffini corpuscles (pressure receptors), Vater-
articular nerve (a prominent branch of the posterior Pacini corpuscles (velocity receptors), and free nerve-
tibial nerve) and from the terminal portions of the ob- endings (pain receptors). These studies indicate that

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I378 I). (‘. (OVEY AND A. A. SAPEGA

disruption of the posterior cruciate ligament alters not confirmed that the fixation site of the femoral graft
only the kinematics of the knee but also the afferent would be the primary determinant of changes in the
signals to the central nervous system. length of the graft during motion of the knee and that
there was no absolutely isometric point within the fem-
Functional Biomechanics
oral attachment zone. These authors proposed that dis-
Effects )J injuries of the Posterior Cruciate Ligament crepancies in the literature pertaining to the variation
tint! the Posterolateral Complex in patterns of the length between the attachment sites
Contemporary research on the mechanical function of individual fibers of the posterior cruciate ligament
and behavior of the posterior cruciate ligament, and of could be explained in part by the varying femoral loca-
the nearby posterolateral ligamentous complex, has pro- tions studied by different investigators4’.
vided an increased awareness of the complicated inter- In a subsequent study of cadavera, done to deter-
relationships that occur under different conditions of mine which portions of the posterior cruciate liga-
motion and loading. There has been no challenge to the ment were isometric during flexion and extension and
long-accepted concept that the posterior cruciate liga- to evaluate stability of the knee, Friederich et al.’35 ob-
ment is the primary restraint to straight posterior trans- served that a small, posterior region of the attachment
lation of the tibia at nearly all positions of flexion of the of the ligament (sites located at the posterosuperior
knee’4’7””’. Isolated loss of this ligament has little effect margin of the femoral origin and at the posterolateral
on tibial rotational laxity or varus and valgus angula- margin of the tibial insertion) exhibited isometric be-
tion. unless there is concomitant injury of the secondary havior. These investigators also noted that fiber attach-
extra-articular restraints’47. A combined rupture of the ment sites centered within the anatomical bulk of the
posterior cruciate ligament and the posterolateral (ar- posterior cruciate ligament moved farther apart as the
cuate) complex results in a marked increase in both knee was flexed and thus did not demonstrate isomet-
varus angulation and external rotation of the tibia at 90 nc (or near-isometric) behavior. Similarly, Trus et al.’’
degrees of flexion, but only small increases in these found that the most isometric femoral point was located
motions occur at full extension4. If the posterior cru- at the posterosuperior margin of the anatomical poste-
ciate ligament is intact but the posterolateral structures nor cruciate-ligament attachment and that a femoral
are torn. a varus moment or external tibial torque will position within the anterior bulk of the ligament was
directly stress the posterior cruciate ligament in posi- highly non-isometric. In a recent in vitro mechanical
tions of flexion of more than 45 degrees77. study, conducted with various motions of the knee joint
and loading conditions (including a procedure to test
Straiti (111(1 Length Behavior ()fthe Fibers isometry), the investigators found, as had Friederich et
(luring Motion ojthe Knee al.36, that the relatively minuscule posterior-oblique fi-
Arms et al’. in an in vitro study, observed that strain bers were the only isometric fibers in the posterior cru-
in the ligament (the per cent change in the length of ciate ligament234. Because this fiber-region composes
the fibers) during motion of the knee varied mark- only about 5 per cent of the substance of the ligament,
edly in different portions of the ligament. Strain in the the authors suggested that use of its sites of attachment
anteriormost fibers increased during flexion from 10 for placement of the graft would leave the anatomical
to 120 degrees, and it was always markedly higher in bulk of the ligament unreconstructed. Most of the liga-
magnitude than in the posteriormost fibers. Studies of ment’s fibers (anterior and central) were found to be
the mechanical and kinematic behavior of the attach- highly non-isometric, first becoming less slack and ul-
ment sites of the posterior cruciate-ligament fibers timately tightening with flexion of the knee. A small,
in specimens from cadavera have shown that the dis- additional posterior-longitudinal fiber-group exhibited
tance between the sites where the individual fibers variable but near-isometric behavior (slight loosening
attach is very sensitive to site variations within the large and retightening with flexion). It has become evident,
(thirty to thirty-five-millimeter-long) zone of femoral from the work of several groups of investigators2435”,
attachment hut is much less sensitive to changes within that the concept of isometric function is difficult to rec-
the region of tibial attachment4ssKn. Hefzy et al”' oncile with the macroscopic anatomy of the bulk of the
studied the patterns of the distances between the sites of posterior cruciate ligament.
attachment of individual fibers of the posterior cruciate Whether it is better to place the posterior cruciate-
ligament. They observed that the distances between the ligament graft in a position where it will function in
sites where most fibers were attached increased with an isometric as opposed to a non-isometric fashion is
flexion of the knee. They thus questioned the prevailing still not settled. Friederich et al.35 recommended iso-
conventional wisdom that a posterior cruciate-ligament metric placement of the graft on the basis of their stud-
graft should optimally be placed at the most isometric ies of stability in the knees of cadavera, reconstructed
femoral position’. Grood et al.4’ investigated changes in either isometrically or anatomically (although there
distance between selected tihial and femoral fiber- was no statistically significant difference between the
attachment sites of the posterior cruciate ligament. They results of the two reconstructive techniques when the

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 INJURIES OF THE POSTERIOR CRUCIATE LIGAMENT 1379

non-isometric, anatomical grafts were secured with the knee is extended, can produce hyperextension com-
knee in 90 degrees of flexion). Petermann et al.”' also bined with a varus moment, resulting in disruption of
advocated isometric positioning of the graft on the ba- the posterolateral structures5. Another, less common
sis of their in vitro investigation of changes in the tibio- mechanism of injury is a severe external-rotation force
femoral distance with motion of the knee. Bomberg et applied to the tibi&#{176}.
al.” arrived at a different conclusion after investigat-
Natural History of Injuries
ing the function of the graft in reconstructed knees of
of the Posterior Cruciate Ligament
cadavera. They found the most satisfactory results, ac-
cording to mechanical and kinematic criteria, when the The natural history of injuries of the posterior cru-
graft had been placed non-isometrically (four to five ciate ligament has been a matter of debate, much of
millimeters of tightening with flexion). Galloway et al.37 which has centered on the long-term sequelae of isolated
recently reported that non-isometric reconstruction and combined injuries. Until relatively recently, there
of the posterior cruciate ligament, with the graft se- was a general consensus in the orthopaedic literature
cured with the knee in 30 degrees of flexion, restored that patients who have an isolated injury of the ligament
the most physiological pattern of tibial motion. Pearsall usually do well when treated non-operatively33””””'
et al.57 found that normal posterior stability was not while those who have combined injuries of the ligament
restored after in vitro reconstruction of the posterior do not’. However, several reports have challenged this
cruciate ligament with use of isometric sites for place- assumption. Dandy and Pusey27 reported that fourteen of
ment of the graft. An earlier, near-corollary observation twenty patients who had an isolated injury of the poste-
by Whiteside et al.”4 was that abnormal laxity in the rior cruciate ligament had pain and nine patients had
knees of cadavera in which the posterior cruciate liga- episodes of giving-way, at a mean duration of follow-up
ment had been sectioned could be corrected with two of seven years. They found no correlation between liga-
grafts that separately reconstructed the posteromedial mentous laxity and the functional results; however, a
and highly non-isometric anterolateral fiber-regions. graded posterior-drawer examination was not used. Sim-
ilarly, Keller et al.59 found that thirty-six (90 per cent) of
Mechanism of Clinical Injury forty patients who had an isolated injury had pain with
Sports-related trauma and motor-vehicle accidents activity, and seventeen patients (43 per cent) had prob-
are the most common causes of injury of the posterior lems with walking, at a mean duration of follow-up of
cruciate ligament53. In a series reported by Kennedy et six years. Decreased function of the knee was associ-
al.”3, twenty-five (42 per cent) of sixty patients sustained ated with an increased interval from the time of the
the injury of the posterior cruciate ligament during ath- injury”9. They also noted a marked increase in roentgeno-
letic activities. Usually the injury was caused by a fall on graphic degenerative changes of the involved knee that
a flexed knee, with the foot plantar flexed, in conjunc- corresponded with the length of time since the injury59.
tion with a powerful posterior force applied to the re- Dejour et al.2” reported that forty (89 per cent) of forty-
gion of the tibial tubercle’9. In vehicular trauma, the five patients had pain when they were evaluated an
posterior cruciate ligament may be injured by a similar average of fifteen years after the injury. These investiga-
mechanism when the flexed knee strikes the dashboard. tors noted that medial tibiofemoral or generalized Os-
Reports have suggested that the posterior cruciate liga- teoarthrosis appeared, on the average, about twenty-five
ment may rupture from an inferiorly directed force ap- years after the injury#{176}.On the basis of long-term follow-
plied to the thigh while the knee is flexed#{176},and from up, they described the natural history of isolated rupture
forced hyperflexion that places an excessive strain on of the posterior cruciate ligament in terms of three post-
most of the fibers. injury phases: first, a phase of functional adaptation,
Certain other mechanisms can cause rupture of the lasting from three to eighteen months; second, a phase of
posterior cruciate ligament, but these are generally as- functional tolerance, continuing for fifteen to twenty
sociated with injuries to other ligaments of the knee. A years; and third, a phase of osteoarthrotic deterioration,
recent study of knees of cadavera indicated that tibial which does not become disabling until after twenty-five
torque, varus-valgus bending moment, and forced hy- years29-”.
perextension were unlikely to cause an isolated injury
Diagnosis
of the posterior cruciate ligament”. Hyperextension
forces can cause tears of the posterior aspect of the History
capsule and the posterior cruciate ligament after the As with other orthopaedic injuries, the initial step in
anterior cruciate ligament has been disrupted35””. A se- the evaluation of an injury of the posterior cruciate
vere varus or valgus bending moment can injure the ligament is to obtain a thorough history (including the
posterior cruciate ligament in combination with an in- mechanism of injury) and to perform a physical exami-
jury of the anterior cruciate ligament or of collateral nation. Patients who have a chronic injury of the liga-
ligaments5”. A posterior force, directed against the me- ment usually have pain as a major symptom; the pain
dial aspect of the proximal part of the tibia while the tends to worsen with time. Some patients also note func-

VOL. 75-A, NO. 9, SEPTEMBER 1993

1380 D. C. COVEY AND A. A. SAPEGA

tional instability, which may limit the type and intensity the quadriceps active test: when the quadriceps is con-
of their activities. tracted by the patient sliding the foot distally against
resistance at the request of the examiner, an anterior
Physical Examination vector force is produced, translating the tibia anteriorly.
Patients who have a suspected injury of the posterior This test was positive in forty-one of forty-two knees
cruciate ligament should be observed carefully for subtle that had documented disruption of the posterior cruci-
changes in gait. The patient may walk with a slightly ate ligament2”.
flexed knee to avoid terminal extension32. Tibone et al.’#{176} The reverse pivot-shift test, reported by Jakob et
observed that flexion of the knee was increased in the al.52, is positive if a reduction sensation is appreciated
mid-stance phase of the gait cycle in patients who had when the flexed, externally rotated knee is extended
an isolated tear of the ligament and in those who had with valgus stress. This test may indicate an injury
combined tears of the posterior cruciate ligament and of the posterior cruciate ligament and the posterolat-
posterolateral structures. These authors postulated that eral complex, but it may be positive in as many as 35 per
the increased flexion was a compensatory mechanism to cent of normal knees examined with the patient under
avoid secondary stresses on the joint and the posterior anesthesia’. Shelbourne et al.”7 described a dynamic
aspect of the capsule, which would be greater in full posterior-shift test, which is positive when a posteri-
extension. orly subluxated tibia suddenly reduces as the flexed
Abrasions, lacerations, or ecchymosis in the region knee is passively extended while the hip is flexed 90
of the tibial tubercle should raise the suspicion of injury degrees. They found this maneuver to be more reliable
of the posterior cruciate ligament”7. With an isolated, than the reverse pivot-shift test. Some patients may be
acute injury, there may be an effusion secondary to a able to reproduce the instability actively (the voluntary
hemarthrosis33, but usually not to the extent seen with a posterolateral-drawer sign) when there is a marked in-
tear of the anterior cruciate ligament. A rupture of the jury of the posterolateral structures”.
posterior cruciate ligament may occur as a component
Imaging Studies
of combined injuries, occasionally as a result of a dis-
location of the knee that has reduced spontaneously Plain roentgenograms of a knee that has an injury
before clinical evaluation7576. A thorough neurovascular of the posterior cruciate ligament may reveal an avul-
examination is essential, and an arteriogram is appropri- sion of the tibia; posterior translation of the tibia on the
ate, if a recent dislocation of the knee is suspecte&. lateral roentgenogram; or, when there is severe lateral
Patients who have a chronic injury of the posterior cru- or posterolateral disruption, avulsion of the fibular head
ciate ligament may have atrophy of the quadriceps73, or the Gerdy tubercle’. In patients who have a chronic
palpable marginal osteophytes, and crepitus. tear of the posterior cruciate ligament, there may be
Injuries of the posterior cruciate ligament and pos- roentgenographic changes consistent with osteoarthro-
terolateral structures of the knee are commonly missed sis of the medial or lateral compartment or with patello-
at the time of the initial evaluation227. Because a rupture femoral osteoarthrosis”’#{176}”.
of the posterior cruciate ligament can be difficult to Magnetic resonance imaging can be an important
diagnose”, it is important that tests specifically for this adjunct to the diagnosis of an injury of the posterior
injury be performed routinely. cruciate ligament. Acute and chronic tears of the liga-
The most accurate passive means of assessment of ment usually appear as foci of increased signal intensity,
the status of the posterior cruciate ligament is the pos- replacing the normally dark ligament, on Tl-weighted
tenor drawer test, performed at 90 degrees of flexion of images74. A recent retrospective study of 201 patients, by
the knee39’42”2. However, Hughston4’ reported that not all Gross et al.43, showed that magnetic resonance imaging
patients who had evidence of an injury of the posterior was 100 per cent sensitive and specific in the diagnosis
cruciate ligament had a positive posterior-drawer sign of injuries of the posterior cruciate ligament. However,
on physical examination. In a modification of the poste- our own clinical experience has demonstrated that
nor drawer test, reported recently by Whipple and El- chronic partial ruptures of the posterior cruciate liga-
lis”3, a posteriorly directed force is applied to the tibia ment with reconstitution, but plastic deformation, of the
while the patient is prone and the knee is in 90 and 45 fibers may occasionally appear unremarkable on mag-
degrees of flexion. These authors stated that an injury netic resonance imaging. even with a clinically obvious
of the posteromedial or posterolateral structures may posterior sag sign.
also be assessed with this maneuver by the noting of any
increased rotation of the forefoot. A rthroscopic Examination

Insall and Hood5 characterized the posterior sag Arthroscopy has also been found to have a high
sign: when the patient who has a complete tear of the degree of accuracy in the diagnosis of injuries of the
posterior cruciate ligament is supine and the knee is posterior cruciate ligament. Lysholm and Gillquist””, us-
flexed 90 degrees, the tibia sags into posterior subluxa- ing a transpatellar ligament portal and both 30 and 70-
tion with respect to the femur. Daniel et al.79 described degree arthroscopes, were able to inspect the posterior

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 INJURIES OF THE POSTERIOR CRUCIATE LIGAMENT 1381

cruciate ligament satisfactorily in 465 (96 per cent) of such as the squat, in which the foot is fixed, produce
484 arthroscopic procedures. A posteromedial portal less tibiofemoral shear force””.
can help the surgeon to obtain a panoramic perspec- Properly performed open-kinetic-chain quadriceps
tive of the mid-substance and distal substance of the exercises may be used, however, as a component of
ligament2. the rehabilitation program. Green et al.#{176},
using a bio-
mechanical simulation to investigate rehabilitation of
Non-Operative Treatment
knees that had a torn posterior cruciate ligament, found
Rationale for Physical Therapy that extension from 70 to 0 degrees of flexion minimized
Many authors have recommended non-operative posterior tibial translation. When isokinetic quadriceps-
treatment for acute or chronic isolated ruptures of the strengthening exercises are prescribed, it is important
posterior cruciate ligament2”2733”#{176}””””#{176}”.
Although reports that the resistance pad be placed at the level of the distal
of series with relatively short-term follow-up have mdi- part of the leg. This position minimizes articular contact
cated that many of these patients were able to function pressure in the medial compartment compared with that
well33””’, recent, longer-term studies have shown that produced by proximal placement of the pad’’ and it also
function of the knee tends to deteriorate over time and reduces posterior tibial translation and concomitant
that most patients are eventually affected by some de- stresses on the secondary restraints2055. Use of a higher-
gree of disability59. This worsening of symptoms is prob- heeled boot or shoe that increases the activity of the
ably due to abnormal forces adversely affecting the quadriceps muscle during the stance phase of gait may
articular surfaces of all three compartments of the knee, help to alleviate symptoms in some patients2”. Patients
as a result of increased posterior tibiofemoral transla- who have symptomatic instability may benefit from
tion””. An in vivo biomechanical study, by Castle et al.”', use of a four-point Donjoy brace (Smith and Nephew
suggested that rupture of the posterior cruciate liga- Donjoy, Carlsbad, California) or a similar brace, but
ment results in posterior tibial subluxation during activ- objective data and long-term follow-up studies on this
ities of daily living that are performed with more flexion mode of treatment are lacking53.
of the knee (such as the ascent and descent of stairs).
Operative Treatment
When the posterior cruciate ligament is torn, the patella
and the patellar ligament are forced to assume a promi- Osseous Avulsion Injuries
nent role in the resistance of posterior tibial transla- Patients in whom the posterior cruciate ligament is
tion’525. In addition, the abnormal posterior tibial sag avulsed with bone can have an excellent result with
produces a shortened moment arm for the quadri- primary operative management if the fragment can be
ceps muscle group, resulting in a decreased mechanical anatomically restored to its bed7””2”'2. If the fragment is
advantage’0. Skyhar et al.’#{176}’
studied articular contact large enough, a single screw is usually sufficient for ef-
pressures in a non-weight-bearing cadaver-knee model fective fixation3”'”. For smaller fragments of bone or
before and after sequential sectioning of the posterior cartilage, sutures pulled through drill-holes have been
cruciate ligament and posterolateral complex. Using used effectively”7’03.
pressure-sensitive film, they found significant increases
in medial and patellofemoral compartment pressures Isolated Injuries of the Posterior Cruciate Ligament
after isolated or combined sectioning of the ligament. The decision as to whether or not to treat isolated
Theoretically, in view of the biomechanics of injuries of tears of the posterior cruciate ligament operatively is
the posterior cruciate ligament, non-operative treatment still a matter of debate. Traditionally, most authors have
should emphasize strengthening of the quadriceps as a recommended non-operative care for all isolated inju-
key component of the physical-therapy program””. Un- ries of the ligament””””#{176}”. More recently, however, others
fortunately, maintenance of good quadriceps strength have advised an operation for young, athletic individu-
does not necessarily correspond with a good long-term als”” or for symptomatic patients who have more than
functional result59. ten to fifteen millimeters of posterior tibial transla-
tion207. Posterior translation of more than fifteen milli-
Rehabilitation after Injuries
meters is indicative of combined injury to the posterior
of the Posterior Cruciate Ligament
cruciate ligament and posterolateral structures39.
During physical therapy, it is important to mini- Although an open procedure may be used for re-
mize posterior tibial translation by protecting against construction of the posterior cruciate ligament”', ar-
gravity-induced posterior tibial sag7’ and by avoid- throscopically assisted techniques have been described
ing open-kinetic-chain hamstring exercises””. In open- recently and hold promise for reduced operative mor-
kinetic-chain exercises, the foot is mobile, and motion bidity and improved clinical results’77”‘’. Arthroscopic-
at the knee joint occurs independently of motion at the ally assisted reconstruction of the ligament is, however,
hip and ankle joints; an example is the leg-curl, which technically demanding. While the many technical as-
strengthens the hamstrings by flexing the knee against pects of this procedure are beyond the scope of the
resistance. In contrast, closed-kinetic-chain exercises, current review, several points should be mentioned,

VOL. 75-A, NO. 9. SEPTEMBER 1993

1382 D. C. COVEY AND A. A. SAPEGA

vantages for reconstruction, including sufficient length

and initial strength, and one non-osseous end, which
facilitates the performance of the 90-degree turn re-
quired to direct the implant from one bone tunnel into
the other22. Apart from the type of allograft tissue, there
are concerns regarding the potential for transmission
of disease, the detrimental effects of sterilization on the
biomechanics of the graft, and possible adverse immu-
nological sequelae2”.

Combined Injuries of the Posterior

Cruciate Ligament and Other Ligaments

The consensus has been that when the posterior

cruciate ligament ruptures in association with another
ligamentous injury, combined operative intervention
offers the potential for a better outcome than non-
operative treatrnent2”4’2’. Combined procedures in-
dude reconstruction, or acute repair and augmentation,
of the posterior cruciate ligament; and repair or recon-
struction of the anterior cruciate ligament and the
posterolateral and posteromedial structures as mdi-
cated27”‘#{176}. However, the results of operative and non-
operative treatment of combined injuries indicate that,
regardless of the treatment, patients who have corn-
bined injuries have a poorer prognosis than those who
have isolated injuries.
Ft;. 2

Sagittal magnetic resonance-imaging scan showing the relatively Results ofRepair and Reconstruction
distal insertion of the posterior cruciate ligament onto the posterior
of the Posterior Cruciate Ligament
tihial shelf.
The goals of operative treatment of tears of the
since they are crucial to the outcome. In order to ap- posterior cruciate ligament include restoration of nor-
proximate an anatomical reconstruction of the posterior mal tibiofemoral stability and kinematics, return to pre-
cruciate ligament, the graft should be placed at the fern- injury levels of activity without pain or instability, and
oral origin of the anterior and central fibers and within reduction in the likelihood or severity of long-term os-
the distalmost region of the tibial insertion (Fig. 2). Use teoarthrosis of the knee. Many operative procedures
of this relatively anterior position on the femur results have been devised for treatment of tears of the posterior
in a non-isometric but anatomical-appearing posterior cruciate ligament, which is an indication that the ideal
cruciate-ligament graft. Such a non-isometric graft will operation has yet to be reported. Procedures involving
not be problematic if it is tensioned and fixed at or near use of the medial head of the gastrocnernius5”3, the
the joint position of maximum intra-articular end-to- semitendinosus and gracihis tendons”””5, the iliotibial
end graft length (70 to 90 degrees of knee flexion). band”, the meniscus”5’5, a synthetic ligament (Gore-
Placement of the graft in a more posterior location on Tex)54, and primary unaugmented repair3””9”’ have all
the femur to achieve a nearly isometric position results failed to produce consistent, objective good and excel-
in a graft that is oriented more vertically than the bulk lent results. The unpredictable outcomes of the different
of the normal posterior cruciate ligament. Great care reconstructive techniques reflect variations in the na-
must be exercised when the tibial tunnel is made, since ture and chronicity of the injury, the type and posi-
the popliteal artery is immediately posterior to the con- tioning of the ligament substitute, the use of synthetic
fluent anatomical insertion of the posterior cruciate hg- augmentation, the position and duration of immobili-
ament and the posterior aspect of the capsule and thus zation of the knee, and the rehabilitation protocol.
may be injured easily5’. Although no reported procedure for reconstruction
Use of allograft for reconstruction of the posterior of the posterior cruciate ligament has yielded results
cruciate ligament is an attractive option because it pre- that are comparable with those obtained with modern
cludes the harvesting of autogenous tissue in a knee techniques for the reconstruction of the anterior cru-
that is already at risk for patellofemoral and tibioferno- ciate ligament, there are indications that some methods
ral osteoarthrosis. Allogeneic bone-patellar ligament- hold promise for more consistently successful outcomes.
bone and Achilles tendon have been used frequently Clancy et al.” used central-third bone-patellar ligament-
as grafts. An Achilles-tendon allograft has technical ad- bone autogenous grafts, formal arthrotomy, and ana-

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 INJURIES OF THE POSTERIOR CRUCIATE LIGAMENT 1383

tomical placement of the graft; they reported good or ber”” recently reported on eighteen patients in whom
excellent results in all of ten patients who had had re- an isolated injury of the posterior cruciate ligament or
pair and reconstruction for an acute mid-substance in- a combined injury of the arcuate complex had been
jury of the posterior cruciate ligament. Reconstruction treated with open or arthroscopically assisted recon-
led to a good or excellent result in eleven of thirteen struction of the ligament (with concomitant posterolat-
patients who had had a chronic, symptomatic tear of eral capsular advancement in patients who had a tear
the posterior cruciate ligament”‘. Although a free autog- of the arcuate complex). Fascia lata, Achilles-tendon,
enous patellar-ligament graft was clinically successful in or patellar-ligament allografts (supplemented with a
most of these patients, studies on animals have sug- ligament-augmentation device in some patients) were
gested that the transplanted tendon may never achieve used for ligament substitution. Although the operation
the characteristics of a normal posterior cruciate liga- did not restore normal anteroposterior tibial translation
ment”'. The open technique of Chancy et al.”' has been in most patients, those who had had an acute injury
modified to an arthroscopic procedure in which an au- fared markedly better over-all than those who had had
togenous graft or an allograft can be used to reconstruct a chronic injury.
the posterior cruciate ligament, with reduced operative In summary, knowledge about the posterior cru-
morbidity compared with use of traditional open tech- ciate ligament lags compared with that pertaining to
niques’722”’”3. Barrett and Savoie7 reported an excellent the anterior cruciate ligament, but this has been rapidly
result in all of four knees that had had repair and recon- changing over the last decade. New studies on the anat-
struction of the posterior cruciate ligament with use of omy, physiology, and biomechanics of the posterior cru-
semitendinosus tendon with Dacron stent augmenta- ciate ligament are stimulating a reassessment of some of
tion. In the remaining fourteen knees in their series the traditional concepts. An understanding of the basic
(which excluded knees that had an isolated tear), nei- science of the posterior cruciate ligament remains a nec-
ther repair with sutures alone nor in combination with essary prelude to advances in the treatment of these
semitendinosus augmentation gave adequate stabihiza- injuries.
tion, at a mean duration of follow-up of five years. Corn- Although it has been well recognized that patients
bination of a posterior cruciate-higament graft with who have combined injuries of the posterior cruciate
synthetic augmentation was shown to increase the initial ligament and other ligaments havenot had a good result
stability of the knee joint in an animal study57, but resul- when managed non-operatively, recent reports5’ de-
tant stress-shielding may have adverse effects on healing scribing the natural history of untreated, isolated inju-
of the graft59. ries of the posterior cruciate ligament have indicated
Maday et al.7’ recently reported their results with use that severe morbidity is the usual result in patients who
of Achilles or patellar-ligament allografts to reconstruct have been followed adequately. The mainstay of non-
isolated and combined injuries of the posterior cruciate operative treatment is rehabilitation of the quadriceps,
ligament in twenty-nine patients. Arthroscopically as- but this does not necessarily prevent long-term osteo-
sisted techniques were used for anatomical reconstruc- arthrosis and dysfunction.
tion of the anterior bulk of the ligament, as advocated Reconstruction of the posterior cruciate ligament
by Clancy et al.’.. Covey et al.223, Bomberg et al.”, and with use of modern operative techniques, guided by re-
others who have believed that anatomical positioning of cent biomechanical data regarding placement of the
the graft is preferable to isometric positioning. At an graft and its effect on function of the knee, may offer
average duration of follow-up of thirty-four months, all the best chance for good long-term results in patients
patients in the series of Maday et al.7’ who had had who have either an isolated injury or combined injuries.
an isolated rupture of the posterior cruciate ligament provided that tibiofemoral stability and kinematics are
had decreased posterior laxity, and most had improved restored. Use of bifid grafts, which allow more faithful
function. Patients who had had combined injuries had reconstruction of the entire macrostructure of the pos-
less improvement, and acutely reconstructed knees ap- tenor cruciate ligament, possibly in combination with
peared to have a better outcome than those that had synthetic augmentation, may ultimately provide addi-
been treated with late reconstruction. Noyes and Bar- tional benefits.

References
I . Arms, S. W.; Johnson, R. J.; and Pope, M. H.: Strain measurement of the human posterior cruciate ligament. Traits. Orthop. Res. Soc., 9:
355. 1984.
2. Anioczky, S. P.; Rubin, R. M.; and Marshall, J. L.: Microvasculature of the cruciate ligaments and its response to injury. An experimental
study in dogs.J. Bone (mi/Joint Surg.. 61-A: 1221-1229. Dec. 1979.
3. Aroen, A.; Strand, T.; and Moister, A.: Primaer sutur av bakre korsband. Tidsskr. Norske Laegeforen., 1 12: 1582-1584. 1992.
4. Bach, B. R.; Daluga, D. J.; Mikosz, R.; Andnacchi, T. P.; and Seidi, R.: Force displacement characteristics of the posterior cruciate
ligament. Am. J. Sports Med.. 20: 67-72. 1992.
5. Baker, C. L., Jr.; Norwood, L. A.; and Hughston, J. C.: Acute posterolateral rotatory instability of the knee. J. Bo,ie and Joint Surg., 65-A:
614-618. June 1983.

VOL. 75-A, NO. 9. SEPTEMBER 1993

1384 D. C. COVEY AND A. A. SAPEGA

6. Baker, C. L., Jr.; Norwood, L. A.; and Hughston, J. C.: Acute combined posterior cruciate and posterolateral instability of the knee. Am.
J. Sports Med., 12: 204-208, 1984.
7. Barrett, 6. R., and Savoie, F. H.: Operative management of acute PCL injuries with associated pathology: long-term results. Orthopedics,
14:687-692. 1991.
8. Barton, T. M.; Torg, J. S.; and Das, M.: Posterior cruciate ligament insufficiency. A review of the literature. Sports Med., 1: 419-430, 1984.
9. Bianchi, M.: Acute tears of the posterior cruciate ligament: clinical study and results of operative treatment in 27 cases. Am. J. Sports
Med., 1 1: 308-314, 1983.
10. Bomberg, B. C.; Acker, J. H.; Boyle, J.; and Zarins, B.: The effect of posterior cruciate ligament loss and reconstruction on the knee. Am.
J. Knee Surg.. 3: 85-96, 1990.
I 1 . Bosch, U., and Kasperczyk, W. J.: Healing of the patellar tendon autograft after posterior cruciate ligament reconstruction - a process
of ligamentization? An experimental study in a sheep model. Am. J. Sports Med., 20: 558-566, 1992.
1 2. Bradley, i.; FitzPatrick, D.; Daniel, D.; Sbercliff, T.; and O’Connor, J.: Orientation of the cruciate ligament in the sagittal plane. A
method of predicting its length-change with flexion.J. Bone andJoint Surg., 70-B(1): 94-99, 1988.
13. Burks, R. T., and Schaffer, J. J.: A simplified approach to the tibial attachment of the posterior cruciate ligament. C/in. Orthop., 254:
216-219. 1990.
14. Butler, D. L.; Noyes, F. R.; and Grood, E. S.: Ligamentous restraints to anterior-posterior drawer in the human knee. A biomechanical
study. J. Bone itid Joint Surg., 62-A: 259-270, March 1980.
15. Cain, T. E., and Schwab, C. H.: Performance of an athlete with straight posterior knee instability. Ani. J. Sports Med., 9: 203-208. 1981.
16. Castle, T. H., Jr.; Noyes, F. R.; and Grood, E. S.: Posterior tibial subluxation of the posterior cruciate-deficient knee. C/in. Orthop., 284:
193-202. 1992.
17. Ciancy, W. C., Jr., and Smith, L.: Arthroscopic anterior and posterior cruciate ligament reconstruction technique. Ann. Chir. Gynaeco!.,
80: 141-148. 1991.
I 8. Ciancy, W. C., Jr.; Narechania, R. G.; Rosenberg, T. D.; Gmeiner, J. G.; Wisnefske, D. D.; and Lange, T. A.: Anterior and posterior
cruciate ligament reconstruction in rhesus monkeys. A histological, microangiographic, and biomechanical analysis. J. Bone and Joint
Surg.. 63-A: 1270-1284, Oct. 1981.
I 9. Clancy, W. G., Jr.; Shelbourne, K. D.; Zoeliner, G. B.; Keene, J. S.; Reider, B.; and Rosenberg, T. D.: Treatment of knee joint instability
secondary to rupture of the posterior cruciate ligament. Report of a new procedure. J. Bone and Joint Surg., 65-A: 310-322, March 1983.
20. Cooper, D. E.; Warren, R. F.; and Warner, J. J. P.: The posterior cruciate ligament and posterolateral structures of the knee: anatomy,
function. and patterns of injury. In instructional Course Lectures, The American Academy of Orthopaedic Surgeons. Vol. 40, pp. 249-270.
Park Ridge. Illinois. The American Academy of Orthopaedic Surgeons. 1991.
21. Covey, D. C., and Wright, D. G.: Bone healing by induction: clinical perspectives. Mi/it. Med., 157: 107-109. 1992.
22. Covey, D. C.; Sapega, A. A.; and Martin, R. C.: Arthroscope-assisted allograft reconstruction of the posterior cruciate ligament. Tech-
nique and hiomechanical considerations.J. Orthop. Tech., 1: 91-97. 1993.
23. Covey, D. C.; Sapega, A. A.; Sherman, G. M.; and Torg, J. S.: Testing for “isometry” during posterior cruciate ligament reconstruction.
Tratis. Orthop. Res. Soc., I 7: 665. 1992.
24. Covey, D. C.; Sapega, A. A.; Sherman, C. M.; and Torg, J. S.: Anatomical and biomechanical factors governing the choice of bone tunnel
location during posterior cruciate ligament reconstruction. Presented as a Scientific Exhibit at the Annual Meeting of The American
Academy of Orthopaedic Surgeons, San Francisco, California, Feb. 18 through 23, 1993.
25. Cross, M. J., and Powell, J. F.: Long-term followup of posterior cruciate ligament rupture: a study of 116 cases. Am. J. Sports Med., 12:
292-297. 1984.
26. Crowninshield, R.; Pope, M. H.; and Johnson, R. J.: An analytical model of the knee. J. Biomech., 9: 397-405. 1976.
27. Dandy, D. J., and Pusey, R. J.: The long-term results of unrepaired tears of the posterior cruciate ligament. J. Bone and Joint Surg.,
64-B(l): 92-94. 1982.
28. Daniel, D. M.; Stone, M. L.; Barnett, P.; and Sachs, R.: Use of the quadriceps active test to diagnose posterior cruciate-ligament
disruption and measure posterior laxity of the knee. J. Bone and Joint Surg., 70-A: 386-391 , March 1988.
29. Dejour, H.; Waich, C.; Peyrot, J.; and Eberhard, P.: The natural history of rupture of the posterior cruciate ligament. Orthop. Trans., 11:
146, 1987.
30. Dejour, H.; Walch, G.; Peyrot, J.; and Eberhard, P.: Histoire naturelle de Ia rupture du ligament crois#{233}post#{233}rieur. Rev. chir. orthop., 74:
35-43, 1988.
3 1 . Dorlot, J.-M.; Christel, P.; Sedel, L.; and Witvoet, J.: The displacement of the bony insertion sites of the cruciate ligaments during the
flexion of the knee. Trans. Orthop. Res. Soc., 8: 328, 1983.
32. Fleming, R. E., Jr.; Blatz, D. J.; and McCarroll, J. R.: Posterior problems in the knee. Posterior cruciate insufficiency and posterolateral
rotatory insufficiency.Am.J. Sports Med., 9: 107-113. 1981.
33. Fowler, P. J., and Messieh, S. S.: Isolated posterior cruciate ligament injuries in athletes. Am. J. Sports Med., 15: 553-557, 1987.
34. Friederich, N. F.; Muller, W.; and O’Brien, W. R.: Klinische Anwendung biomechanischer und funktionell anatomischer Daten am
Kniegelenk. Orthopade, 21:41-50, 1992.
35. Friederich, N. F.; O’Brien, W. R.; Muller, W.; and Henning, C. E.: How important is isometric placement of cruciate ligament substitutes?
Presented as a Scientific Exhibit at the Annual Meeting of The American Academy of Orthopaedic Surgeons. New Orleans. Louisiana,
Feb. 8 through 13. 1990.
36. Fuss, F. K.: The restraining function of the cruciate ligaments on hyperextension and hyperflexion of the human knee joint. Anat. Rec.,
230: 283-289. 1991.
37. Galloway, M.; Mehalik, J.; Crood, E.; Levy, M.; and Noyes, F.: Tibial displacement following reconstruction of the posterior cruciate
ligament: the effect of knee position during graft fixation. Orthop. Trans., 17: 225, 1993.
38. Girgis, F. 6.; Marshall, J. L.; and Al Monajem, A. R. S.: The cruciate ligaments of the knee joint. Anatomical, functional and experimen-
tal analysis. C/in. Orthop., 106: 216-231. 1975.
39. Gollehon, D. L.; Torzilii, P. A.; and Warren, R. F.: The role of the posterolateral and cruciate ligaments in the stability of the human
knee. A biomechanical study.J. Bone andJoint Surg., 69-A: 233-242, Feb. 1987.
40. Green, R. B.; Noble, P. C.; Woods, G. W.; and Tulios, H. S.: Rehabilitation of the posterior cruciate deficient knee: a biomechanical
simulation. Orthop. Trans.. 13: 319. 1989.

THE JOURNAL OF BONE AND JOINT SURGERY

 INJURIES OF THE POSTERIOR CRUCIATE LIGAMENT 1385

41. Grood, E. S.; Hefzy, M. S.; and Lindenfield, T. N.: Factors affecting the region of most isometric femoral attachments. Part I: the
posterior cruciate ligament. Am. J. Sports Med., 17: 197-207, 1989.
42. Grood, E. S.; Stowers, S. F.; and Noyes, F. R.: Limits of movement in the human knee. Effect of sectioning the posterior cruciate
ligament and posterolateral structures. J. Bone and Joint Surg., 70-A: 88-97, Jan. 1988.
43. Gross, M. L.; Grover, J. S.; Bassett, L. W.; Seeger, L. L.; and Finerman, G. A.: Magnetic resonance imaging of the posterior cruciate
ligament. Clinical use to improve diagnostic accuracy. Am. J. Sports Med., 20: 732-737, 1992.
44. Harner, C. D.; Olson, E. J.; Fu, F. H.; Irrgang, J. J.; and Maday, H. G.: The use of fresh frozen allograft tissue in knee ligament
reconstruction: indications, results, techniques and controversies. Presented as a Scientific Exhibit at the Annual Meeting of The
American Academy of Orthopaedic Surgeons, Washington, D.C., Feb. 20 through 25, 1992.
45. Harner, C. D.; Livesay, 6. A.; Choi, N. Y.; Fujie, H.; Fu, F. F.; and Woo, S. L.-Y.: Evaluation of the sizes and shapes of the human anterior
and posterior cruciate ligaments: a comparative study. Trans. Orthop. Res. Soc., 17: 123, 1992.
46. Hefzy, M. S.; Grood, E. S.; and Lindenfeld, T. L.: The posterior cruciate ligament: a new look at length patterns. Trans. Orthop. Ret. Soc.,
11: 128. 1986.
47. Heller, L., and Langman, J.: The menisco-femoral ligaments of the human knee.J. Bone andJoint Surg., 46-B(2): 307-313, 1964.
48. Hughston, J. C.: The absent posterior drawer test in some acute posterior cruciate ligament tears of the knee. Am. J. Sports Med., 16:
39-43. 1988.
49. Hughston, J. C.; Bowden, J. A.; Andrews, J. R.; and Norwood, L. A.: Acute tears of the posterior cruciate ligament. Results of operative
treatment. J. Bone and Joint Surg., 62-A: 438-450, April 1980.
50. Insall, J. N., and Hood, R. W.: Bone-block transfer of the medial head of the gastrocnemius for posterior cruciate insufficiency. J. Bone
and Joint Surg.. 64-A: 691-699, June 1982.
5 1 . Jackson, D. W.; Proctor, C. S.; and Simon, T. M.: Arthroscopic assisted PCL reconstruction: a technical note on potential neurovascular
injury related to drill hit configuration. Arthroscopy, 9: 224-227. 1993.
52. Jakob, R. P.; Hassler, H.; and Staeubli, H. U.: Observations on rotatory instability of the lateral compartment of the knee. Experimental
studies on the functional anatomy and the pathomechanism of the true and the reversed pivot shift sign. Acta Orthop. Scandinavica,
52 (Supplementum 191): 1-32. 1981.
53. Johnson, C. J., and Bach, B. R.: Current concepts review. Posterior cruciate ligament. Am. J. Knee Surg., 3: 143-153, 1990.
54. Jones, R. C., and Richardson, A. B.: Gore-Tex posterior cruciate ligament replacement - preliminary clinical results. Orthop. Trans., 14:
123-124. 1990.
55. Jurist, K. A., and Otis, J. C.: Anteroposterior tibiofemoral displacements during isometric extension efforts. The roles of external load
and knee tlexion angle. A,z. J. Sports Med., 13: 254-258. 1985.
56. Kasperczyk, W. J.; Bosch, U.; Oestern, H. J.; and Tscherne, H.: Influence of immobilization on autograft healing in the knee joint. A
preliminary study in a sheep knee PCL model.Arch. Orthop. and Trau,nat. Surg., 110: 158-161, 1991.
57. Kasperczyk, W. J.; Bosch, U.; Geisler, A.; Cordes, H.; Oestern, H. J.; and Tscherne, H.: The early stability of posterior cruciate ligament
replacement with a free patellar tendon graft under immediate rehabilitation conditions. Orthop. Trans., 13: 348-349, 1989.
58. Katonis, P. C; Assimakopoulos, A. P.; Agapitos, M. V.; and Exarchou, E. I.: Mechanoreceptors in the posterior cruciate ligament.
Histologic study on cadaver knees. Acta Orthop. Scandinavica, 62: 276-278, 1991.
59. Keller, P. M.; Shelbourne, K. D.; McCarroll, J. R.; and Rettig, A. C.: Nonoperatively treated isolated posterior cruciate ligament injuries.
Am.J. Sports Med., 21: 132-136, 1993.
60. Kennedy, J. C., and Grainger, R. W.: The posterior cruciate ligament. J. Trauma, 7: 367-377, 1967.
61 . Kennedy, J. C.; Alexander, I. J.; and Hayes, K. C.: Nerve supply of the human knee and its functional importance. Arz. J. Sports Med., 10:
329-335. 1982.
62. Kennedy, J. C.; Hawkins, R. J.; and Willis, R. B.: Strain gauge analysis of knee ligaments. C/in. Orthop., 129: 225-229, 1977.
63. Kennedy, J. C.; Roth, J. H.; and Walker, D. M.: Posterior cruciate ligament injuries. Orthop. Digest, 7: 19-32, 1979.
64. Kurosawa, H.; Yamakoshi, K.-I.; Yasuda, K.; and Sasaki, T.: Simultaneous measurement of changes in length of the cruciate ligaments
during knee motion. C/in. Orthop.. 265: 233-240. 1991.
65. Lindstr#{246}m, N.: Cruciate ligament plastics with meniscus [abstract]. Acta Orthop. Scandinavica, 29: 150-152, 1960.
66. Lipscomb, A. B.; Anderson, A. F.; Norwig, E. D.; Hovis, W. D.; and Brown, D. L.: Isolated posterior cruciate Jigament reconstruction.
Long-term results. An:. I. Sports Med., 21: 490-496. 1993.
67. Loos, W. C.; Fox, J. M.; Blazina, M. E.; Del Pizzo, W.; and Friedman, M. J.: Acute posterior cruciate ligament injuries. Am. J. Sports Med.,
9:86-92, 1981.
68. Lutz, C. E.; Palmitier, R. A.; An, K. N.; and Chao, E. V. S.: Comparison of tibiofemoral joint forces during open-kinetic-chain and
closed-kinetic-chain exercises. I Bone and Joint Surg., 75-A: 732-739, May 1993.
69. Lysholm, J., and Gillquist, J.: Arthroscopic examination ofthe posterior cruciate ligament.J. Bone andJoint Surg., 63-A: 363-366. March 1981.
70. McMaster, W. C.: Isolated posterior cruciate ligament injury: literature review and case reports.J. Trauma, 15: 1025-1029, 1975.
71. Maday, M.; Fu, F. H.; Harner, C. D.; and Irrgang, J. J.: Posterior cruciate ligament reconstruction using fresh frozen allograft tissue:
indications, techniques. results and controversies. Presented as a Scientific Exhibit at the Annual Meeting of The American Academy of
Orthopaedic Surgeons. San Francisco, California, Feb. 18 through 23, 1993.
72. Markolf, K. L.; Wascher, D. C.; and Finerman, 6. A. M.: Direct in vitro measurement of forces in the cruciate ligaments. Part II: the
effect of section of the posterolateral structures. J. Bone andJoint Surg., 75-A: 387-394, March 1993.
73. Miniaci, A.; Shields, C. L.; Tibone, J. E.; Patek, R.; Perry, J’ and Pink, M.: Functional analysis of the posterior cruciate deficient knee.
Ort/zop. ir(iFi.S. 15: 176-177. 1991.
74. Mink, J. H.; Reicher, M. A.; and Crues, J. V., III: Magnetic Resonance Imaging ofihe Knee. New York. Raven Press. 1987.
75. Montgomery, J. B.: Dislocation of the knee. Orthop. C/in. North America, 18: 149-156, 1987.
76. Moore, H. A., and Larson, R. L.: Posterior cruciate ligament injuries. Results of early surgical repair. Am. J. Sports Med., 8: 68-78, 1980.
77. Neurath, M., and StofTt, E.: Faszikul#{228}re und subfaszikul#{228}re Architektur der Ligamenta cruciata. Unfallchirurgie, 18: 125-132, 1992.
78. Nielsen, S., and Helmig, P.: Posterior instability of the knee joint. An experimental study. Arch. Orthop. and Traumat. Surg., 105: 121-
125. 1986.
79. Nielsen, S.; Ovesen, J.; and Rasmussen, 0.: The posterior cruciate ligament and rotatory knee instability. An experimental study. Arch.
Ortliop. (111(1 Trau,nat. Surg.. 1()4: 53-56. 1985.

VOL. 75 -A. NO. 9. SEPIEM BE R I 993

1386 D. C. COVEY AND A. A. SAPEGA

80. Noyes, F. R., and Barber, S. D.: Allograft reconstruction of the anterior and posterior cruciate ligaments: report of ten-year experience
and results. In Instructional Course Lectures, The American Academy of Orthopaedic Surgeons. Vol. 42. pp. 381-396. Rosemont, Illinois,
The American Academy of Orthopaedic Surgeons. 1993.
81 . O’Brien, W. R.; Friedench, N. F.; Muller, W.; and Henning, Cd Functional anatomy of the cruciate ligaments and their substitutes.
Presented as a Scientific Exhibit at the Annual Meeting of The American Academy of Orthopaedic Surgeons. Las Vegas. Nevada,
February 9 through 14. 1989.
82. O’Donnell, T. F., Jr.; Brewster, D. C.; Darling, R. C.; Veen, H.; and Waitman, A. A.: Arterial injuries associated with fractures and/or
dislocations of the kneel Trauma, 17: 775-784. 1977.
83. Ogata, K.: Posterior cruciate ligament reconstruction: a comparative study of two different methods. Bull. Hosp. Joint Dis., 51: 186-
198. 1991.
84. Ogata, K., and McCarthy, J. A.: Measurements of length and tension patterns during reconstruction of the posterior cruciate ligament.
Ani. J. Sports Med., 20: 351-355, 1992.
85. Ogata, K.; McCarthy, J. A.; Dunlap, J.; and Manske, P. R.: An experimental study of posterior sag of the tibia in posterior cruciate
deficient knee. Trans. Orthop. Res. Soc., 13: 279. 1988.
86. Parolie, J. M., and Bergfeld, J. A.: Long-term results of nonoperative treatment of isolated posterior cruciate ligament injuries in the
athlete. Am. J. Sports Med., 14: 35-38, 1986.
87. Pearsall, A. W.; Draganich, L. F.; Larkin, J. J.; Pyevich, M.; and Reider, B.: An in vitro analysis of knee stability after reconstruction of
the posterior cruciate ligament. Orthop. Trans., 16: 322. 1992.
88. Petermann, J.; Gotzen, L.; and Trus, P.: Wiederherstellende Eingriffe am hinteren Kreuzband - Experimentelle Untersuchungen zur
Isometric. Teil II: Untersuchungen am HKB-Ersatzmodell. Unfallchirurgie, 95: 354-357, 1992.
89. Pournaras, J., and Symeonides, P. P.: The results of surgical repair of acute tears of the posterior cruciate ligament. C/in. Orthop., 267:
103-107. 1991.
90. Race, A., and Amis, A. A.: Mechanical properties of the two bundles of the human posterior cruciate ligament. Trans. Orthop. Res. Soc.,
17: 124. 1992.
9 1 . Rosenberg, T. D.; Paulos, L. E.; and Abbott, P. J., Jr.: Arthroscopic cruciate repair and reconstruction: an overview and descriptions of
technique. In The Crucial Ligaments: Diagnosis and Treatment of Ligamentous Injuries about the Knee, pp. 409-423. Edited by J. A.
Feagin, Jr. New York. Churchill Livingstone. 1988.
92. Ross, A. C., and Chesterman, P. J.: Isolated avulsion of the tibial attachment of the posterior cruciate ligament in childhood. J. Bone
andJoint Surg., 68-B(S): 747. 1986.
93. Roth, J. H.; Bray, R. C.; Best, T. M.; Cunning, L. A.; and Jacobson, R. P. Posterior cruciate ligament reconstruction by transfer of the
medial gastrocnemius tendon. Am. J. Sports Med.. 16: 21-28, 1988.
94. Satku, K.; Chew, C. N.; and Seow, H.: Posterior cruciate ligament injuries. Acta Orthop. Scandinavica, 55: 26-29, 1984.
95. Scapinelli, R.: Studies on the vasculature of the human knee joint. Acta Anat., 70: 305-331, 1968.
96. Schultz, R. A.; Miller, D. C.; Kerr, C. S.; and Micheli, L.: Mechanoreceptors in human cruciate ligaments. A histological study. J. Bone
(fll(/Joitlt Surg., 66-A: 1072-1076. Sept. 1984.
97. Shelbourne, K. D.; Benedict, F.; McCarroll, J. R.; and Rettig, A. C.: Dynamic posterior shift test. An adjuvant in evaluation of posterior
tibial subluxation. Am. J. Sports Med., 17: 275-277, 1989.
98. Shino, K.; Shuji, H.; and Ono, K.: The voluntarily evoked posterolateral drawer sign in the knee with posterolateral instability. C/in.
Ortliop., 215: 179-186. 1987.
99. Shirakura, K.; Kato, K.; and Udagawa, E.: Characteristics of the isokinetic performance of patients with injured cruciate ligaments. Am.
J. Sports Med.. 20: 754-76(), 1992.
lOt). Sidles, J. A.; Larson, R. V.; Garbini, J. L.; Downey, D. J. and Matsen, F. A., III: Ligament length relationships in the moving knee.
J. Orthop. Res.. 6: 593-610. 1988.
101. Skyhar, M. J.; Warren, R. F.; Ortiz, G. J.; Schwartz, E.; and Otis, J. C.: The effects of sectioning of the posterior cruciate ligament and
the posterolateral complex on the articular contact pressure within the knee.J. Bone andJoint Surg., 75-A: 694-699, May 1993.
102. Strand, T.; Moister, A. 0.; Engesaeter, L. B.; Raugstad, T. S.; and Aiho, A.: Primary repair in posterior cruciate ligament injuries. Ada
Orthop. Scandinavica, 55: 545-547, 1984.
103. Suprock, M. D., and Rogers, V. P.: Posterior cruciate avulsion. Orthopedics, 13: 659-662. 1990.
1(14. Tibone, J. E.; Antich, T. J.; Perry, J.; and Moynes, D.: Functional analysis of untreated and reconstructed posterior cruciate ligament
injuries. Ani. J. Sports Med., 16: 217-223, 1988.
105. Tillberg, B.: The late repair of torn cruciate ligaments using menisci.J. Bone andfoint Surg., 59-B(1): 15-19. 1977.
1(16. Torg, J. S.; Barton, T. M.; Pavlov, H.; and Stine, R.: Natural history of the posterior cruciate ligament-deficient knee. C/in. Orthop.. 246:
208-216. 1989.
107. Trent, P. S.; Walker, P. 5.; and Wolf, B.: Ligament length patterns, strength. and rotational axes of the knee joint. C/in. Orthop., 117:
263-270, 1976.
108. Trickey, E. L.: Injuries to the posterior cruciate ligament: diagnosis and treatment of early injuries and reconstruction of late instability.
Cliii. Orthop., 147: 76-81 . 1980.
109. Trus, P.; Gotzen, L.; and Petermann, J.: Wiederherstellende Eingriffe am hinteren Kreuzband - Experimentelle Untersuchungen zur
Isometric. Teil I: Untersuchungen am Fadenmodeil. Unfallchirurgie, 95: 349-353, 1992.
I 10. Van Dommelen, B. A., and Fowler, P. J. Anatomy of the posterior cruciate ligament. A review. Am. J. Sports Med., 17: 24-29, 1989.
I 1 1. Viadimirov, B.: Arterial sources of blood supply of the knee-joint in man. Ada Med., 47: 1-10, 1968.
1 1 2. Wascher, D. C.; Markolf, K. L.; Shapiro, M. S.; and Finerman, G. A. M.: Direct in vitro measurement of forces in the cruciate ligaments.
Part I: The effect of multiplane loading in the intact kneel Bone andJoint Surg., 75-A: 377-386, March 1993.
1 13. Whipple, T. L., and Ellis, F. D.: Posterior cruciate ligament injuries. C/in. Sports Med., 10: 515-527. 1991.
1 14. Whiteside, L. A.; Kasselt, M. R.; and Haynes, D. W.: Anatomical rationale for triple reconstruction of the posterior cruciate ligament.
Tran.s Orthop. Ret. Soc., 7: 361 . 1982.
1 15. Wirth, C. J., and Jager, M.: Dynamic double tendon replacement of the posterior cruciate ligament. Am. J. Sports Med., 12: 39-43, 1984.

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