Hip Kinematics During Single-Leg Tasks in People With and Without Hip-Related Groin Pain and the Association Among Kinematics, Hip Muscle Strength, and Bony Morphology.

Objective: To compare 3-D hip kinematics during the single-leg squat and step-down in patients with hip-related groin pain to those in asymptomatic participants, and to assess relationships among hip kinematics, muscle strength, and bony morphology.
Design: Controlled laboratory cross-sectional study.
Methods: Forty patients with hip-related groin pain and 40 matched, asymptomatic participants between 18 and 40 years of age participated. A handheld dynamometer was used to assess hip abductor and external rotator strength. An 8-camera motion-analysis system was used to quantify 3-D kinematics during the single-leg squat and step-down. Magnetic resonance imaging was used to quantify bony morphology. The independent t test and Mann-Whitney U test were used to assess between-group differences. Pearson coefficient correlations were used to assess relationships.
Results: Patients with hip-related groin pain had smaller peak hip flexion angles, smaller knee flexion angles, and lesser squat depth compared to asymptomatic participants during the single-leg squat. Among patients with hip-related groin pain, smaller hip flexion angles during the single-leg squat were associated with hip abductor weakness ( r = 0.47, P ≤.01). Among asymptomatic participants, smaller peak hip flexion angles during the single-leg squat were associated with less acetabular coverage ( r = 0.33, P = .04) and shallow squat depth ( r = 0.48, P ≤.01); a smaller hip internal rotation angle during the step-down was associated with larger femoral neck shaft angle ( r = -0.43, P <.01).
Conclusion: Compared to asymptomatic participants, patients with hip-related groin pain had smaller hip and knee flexion angles and shallower squat depth during the single-leg squat. Smaller hip flexion angles were associated with hip abductor weakness among those with hip-related groin pain. J Orthop Sports Phys Ther 2020;50(5):243-251. Epub 6 Jan 2020. doi:10.2519/jospt.2020.9150 .