Hip Biomechanics During a Single-Leg Squat: 5 Key Differences Between People With Femoroacetabular Impingement Syndrome and Those Without Hip Pain

Background: The hip joint biomechanics of people with femoroacetabular impingement (FAI) syndrome are different from those of healthy people during a double-leg squat. However, information on biomechanics during a single-leg squat is limited.

Objectives: To compare hip joint biomechanics between people with FAI syndrome and people without hip pain during double-leg and single-leg squats.

Methods: Fourteen people with FAI syndrome (cam, n = 7; pincer, n = 1; mixed, n = 6) and 14 people without hip pain participated in this cross-sectional, case-control, laboratory-based study. Three-dimensional biomechanics data were collected while all participants performed a double-leg and a single-leg squat. Two-way mixed-model analyses of variance were used to assess group-by-task interactions for hip joint angles, thigh and pelvis segment angles, hip joint internal moments, and squat performance variables. Post hoc analyses for all variables with a significant group-by-task interaction were performed to identify between-group differences for each task.

Results: There were significant group-by-task interactions for peak hip joint (P = .014, η² = 0.211) and thigh segment (P = .009, η² = 0.233) adduction angles, and for peak hip joint abduction (P = .002, η² = 0.308) and extension (P = .016, η² = 0.203) internal moments. There were no significant group-by-task interactions for squat performance variables.

Conclusion: Biomechanical differences at the hip between people with FAI syndrome and those without hip pain were exaggerated during a single-leg squat compared to a double-leg squat task.

Level of evidence: Diagnosis, level 4. J Orthop Sports Phys Ther 2019;49(12):908-916. Epub 23 Jul 2019. doi:10.2519/jospt.2019.8356.