Lower Body Functional Performance and Isometric Muscle Strength in Adults With Hip Dysplasia Compared to Healthy Participants – A Cross-sectional Study

OBJECTIVE: To compare functional performance and isometric maximum voluntary contraction during hip flexion, extension, and abduction between patients with hip dysplasia scheduled for periacetabular osteotomy and healthy participants. DESIGN: Cross-sectional study. METHODS: The single-leg hop for distance, Y Balance Test, and maximum voluntary contraction tests in an isokinetic dynamometer were compared between patients and healthy participants. The statistical methods applied were t tests and regression analysis. RESULTS: Fifty-nine patients (mean age: 28 years; 86% women) and 39 healthy participants (mean age: 27 years; 74% women) were included. The single-leg hop test showed a 4.2-cm (95% confidence interval [CI]: 0.3, 8.0) difference between the index and contralateral leg for patients. Healthy participants hopped 34.3 cm (95% CI: 23.2, 45.4) longer than patients. The Y Balance Test indicated a difference in the posterolateral direction between patients’ hips, while healthy participants performed better in all directions. Muscle strength was comparable between patients’ index and contralateral hip. Hip abduction and extension were comparable between groups, but hip flexion was 14.9 N·m (95% CI: 3.9, 26.4) lower in patients. CONCLUSION: Patients with hip dysplasia had significantly worse functional performance in single-leg hop and Y Balance Test, and significant deficit in hip flexion strength compared to healthy participants. JOSPT Open 2025;3(3):310-318. Epub 24 April 2025. doi:10.2519/josptopen.2025.0141