Kinematic Differences During Single-Leg Step-Down Between Individuals With Femoroacetabular Impingement Syndrome and Individuals Without Hip Pain

STUDY DESIGN: Controlled laboratory study, case-control design. BACKGROUND: Despite recognition that femoroacetabular impingement syndrome (FAIS) is a movement-related disorder, few studies have examined dynamic unilateral tasks in individuals with FAIS. OBJECTIVES: To determine whether movements of the pelvis and lower extremities in individuals with FAIS differ from those in individuals without hip pain during a single-leg step-down, and to analyze kinematic differences between male and female participants within groups. METHODS: Individuals with FAIS and individuals without hip pain performed a single-leg step-down while kinematic data were collected. Kinematics were evaluated at 60 degrees of knee flexion. A linear regression analysis assessed the main effects of group, sex, and side, and the interaction of sex by group. RESULTS: Twenty individuals with FAIS and 40 individuals without hip pain participated. Individu-als with FAIS performed the step-down with greater hip flexion (4.9 degrees; 95% confidence interval [CI]: 0.5 degrees, 9.2 degrees) and anterior pelvic tilt (4.1 degrees; 95% CI: 0.9 degrees, 7.3 degrees) than individuals without hip pain. Across groups, female participants performed the task with more hip flexion (6.1 degrees; 95% CI: 1.7 degrees, 10.4 degrees), hip adduction (4.8 degrees; 95% CI: 2.2 degrees, 7.4 degrees), anterior pelvic tilt (5.8 degrees; 95% CI: 2.6 degrees, 9.0 degrees), pelvic drop (1.4 degrees; 95% CI: 0.3 degrees, 2.5 degrees), and thigh adduction (2.7 degrees; 95% CI: 1.3 degrees, 4.2 degrees) than male participants. CONCLUSION: The results of this study suggest that individuals with FAIS have alterations in pelvic motion during a dynamic unilateral task. The noted altered movement patterns in the FAIS group may contribute to the development of hip pain and may be due to impairments that are modifiable through rehabilitation.