Abstract
Background and Objectives: Chronic ankle instability (CAI), a prevalent injury among female volleyball players, can negatively affect functional performance and increase the risk of further injury. The aim of this study was to compare functional movement quality, dynamic balance, vertical jumping performance, hip muscle strength, and risk of injury between adolescent female volleyball players with unilateral CAI and those without CAI. Materials and Methods: This cross-sectional study included 46 adolescent female volleyball players, divided into CAI (n = 23) and control (n = 23) groups based on predefined criteria. Functional movement quality was assessed using the Functional Movement Screen (FMS), and dynamic balance was evaluated with the Y-Balance Test (YBT). Maximal isometric strength of the hip muscles (flexors, extensors, abductors, adductors, and internal and external rotators) was measured using hand-held dynamometry, and vertical jumping performance was assessed using countermovement jump tests. Injury risk was classified based on established cut-off values for the FMS-composite and YBT-anterior reach asymmetry scores. Results: The CAI group demonstrated significantly lower FMS-composite scores (p = 0.007), reduced anterior reach on the YBT (p = 0.004), and decreased strength in the hip flexors (p = 0.007) and hip adductors (p = 0.044), supported by moderate effect sizes. No significant group differences were observed in the other YBT directions, vertical jump tests, or the other hip muscles (p > 0.05). A greater proportion of athletes in the CAI group were classified as high risk for injury based on both FMS-composite (p = 0.022) and YBT-anterior reach asymmetry (p = 0.001) cut-off values, supported by moderate and relatively strong effect sizes, respectively. Conclusions: Adolescent female volleyball players with unilateral CAI showed impaired movement quality, balance deficits, hip muscle weakness, and increased injury risk. These results highlight the importance of targeted interventions and broader investigations into CAI in adolescent athletes.