Degree of Hallux Valgus Is Associated With Dynamic Foot and Knee Kinematics in Ballet Turnout Movements

Background: Hallux valgus (HV) is a common forefoot deformity that may compromise lower-extremity biomechanics, particularly during turnout movements in ballet. However, the kinematic consequences of dynamic high-load, turnout-specific dance tasks remain unclear. This study investigated the relationship between the degree of HV and lower-extremity joint kinematics in ballet dancers. Methods: Fourteen female ballet dancers with visible HV (mean HV angle: 26.5 ± 8.6 degrees) performed 3 tasks: demi-plié, sauté , and grand jeté . A 10-camera motion capture system and a force plate were used to assess foot and knee kinematics during task-specific peak-load phases. Results: Across tasks, the mean medial longitudinal arch angle ranged from approximately 136 to 141 degrees. Significant positive correlations were observed between HV angle and midfoot-forefoot inversion during all tasks ( r = 0.61-0.76, P < .05). During the grand jeté , a greater degree of HV was also associated with an increased medial longitudinal arch angle ( r = 0.64, P = .04), greater knee valgus ( r = 0.64, P = .04), and reduced hindfoot-midfoot inversion ( r = −0.64, P = .04), reflecting a pronated foot posture and altered kinetic chain alignment. Conclusion: In this small case series, greater HV was correlated with altered foot and knee kinematics, particularly under high-load, single-leg conditions. These results underscore the importance of task-specific assessments in dancers. Level of Evidence: Level IV, case series.