OBJECTIVES: (i) Investigate if lower-limb running biomechanics differ between women and men with femoroacetabular impingement syndrome, and (ii) explore whether sex-specific relationships between lower-limb running biomechanics and symptom severity and sport-related concerns exist. DESIGN: Cross-sectional. SETTING: Gait laboratory. PARTICIPANTS: Twenty women and 22 men enrolled in a clinical trial of physiotherapist-led treatments for femoroacetabular impingement syndrome. MAIN OUTCOME MEASURES: Kinematics and kinetics of hip, knee, and ankle joints during the stance phase (calculated from three-dimensional biomechanics data) were compared using statistical parametric mapping. The International Hip Outcome Tool-33 and Copenhagen Hip and Groin Outcomes Score quantified hip-related symptom severity and sport-related concerns. RESULTS: Women had larger hip adduction angles (34%-44% of stance,p = 0.045) than men. For kinetics, women displayed larger external hip extension moments (77%-100%,p = 0.001), smaller knee extension moments (80%-100%,p = 0.007), and smaller ankle dorsiflexion moments (26%-67%,p <
0.001) than men. Worse sport-related concern was associated with a larger peak hip extension angle (0.18, 95%CI 0.05,0.31) and smaller hip flexion moment impulse (0.14∗10 CONCLUSIONS: Women and men with FAI syndrome display differences in lower-limb running biomechanics and relationships between symptom severity and running biomechanics are sex-dependent, warranting consideration in future analyses.