Individuals With Femoroacetabular Impingement Demonstrate Decreased Hip And Pelvis Sagittal Motion During Maximum Depth Squatting

Abstract

Femoroacetabular impingement (FAI) is an anatomically defined condition resulting in abutment of the femoral head or neck with the acetabulum. Despite the growing awareness of this condition by sports medicine specialists as a cause of anterior hip pain, little is known of the kinematic factors that may contribute to this condition. PURPOSE: To compare hip, femur, and pelvis kinematics between individuals with FAI and control subjects during a maximum depth squat. METHODS: Maximum depth squatting was performed by 7 subjects with a confirmed diagnosis of FAI (5 female, 2 male) and 6 control subjects (3 female, 3 male). Kinematic data were collected at 250 Hz using a Qualysis Motion Capture System (Qualysis, Inc., Gothenberg, Sweden). Sagittal plane hip kinematics as well as femur and pelvis motion (relative to the lab coordinate system) at maximum squat depth were compared between groups using independent t-tests (α =0.05). RESULTS: At maximum squat depth, the FAI group demonstrated decreased peak hip flexion (98.4 ± 5.7° vs. 106.5 ± 7.1°, p=0.023) and decreased femoral flexion (85.2 ± 7.2° vs. 99.2 ± 19.0°, p=0.048). There was a trend toward increased pelvis anterior tilt in the FAI group however this difference was not statistically significant (13.5 ± 8.7° vs. 8.6 ± 12.6°, p=0.42). CONCLUSIONS: The decreased hip flexion in the FAI group at maximum squat depth was primarily the result of decreased femoral flexion as FAI subjects demonstrated a tendency towards greater degrees of anterior pelvis tilt. We theorize that the inability of the pelvis to rotate posteriorly at maximum squat depth may be a contributing factor with respect to bony impingement. Hypothetically, more relative posterior tilt of the pelvis during this phase of squatting cycle may allow for greater femoral flexion, and therefore greater hip flexion. Our results suggest that diminished pelvis motion during activities that require high degrees of hip flexion may be a contributing factor to FAI.