Football Players With Hip Dysplasia: The Relationship Between Muscle Strength, Functional Performance, Self-reported Sport and Recreation, Cartilage Defects, and Sex. A Cross-sectional Study

OBJECTIVE: In symptomatic football players with hip dysplasia, we aimed to explore the relationships between self-reported sport and recreation ability and (1) hip muscle strength, (2) functional performance, and investigate if these relationships were modified by sex or cartilage defects. METHODS: In this cross-sectional study, football players (n = 50) with longstanding (>6 months) hip and/or groin pain, a positive flexion/adduction/internal rotation test, and a lateral-center-edge angle <25° were included. Hip muscle strength and functional performance were assessed. Self-reported sport and recreation ability was quantified using the sports and recreational subscales from the International Hip Outcome Tool-33 (iHOT-Sport) and the Copenhagen Hip and Groin Outcome Score (HAGOS-Sport). Relationships were evaluated using regression models with sex and cartilage defects as potential effect modifiers. RESULTS: There was a positive linear relationship between the one-leg-rise test and the iHOT-Sport subscale (β = 0.61; 95% CI: 0.09, 1.14). A polynomial (concave) relationship was found between peak eccentric adduction strength and the HAGOS-Sport subscale (β = -30.88; 95% CI: -57.78, -3.99). Cartilage defects modified the relationship between peak isometric adduction strength and HAGOS-Sport, with those with cartilage defects having a polynomial (convex) relationship (β = 36.59; 95% CI: 12.74, 60.45), and those without cartilage defects having no relationship. CONCLUSION: One-leg-rise performance and adduction strength were associated with self-reported sport and recreation ability, indicating a possible relationship between physical function, hip joint structure, and sport and recreation ability in football players with hip dysplasia.