Lower limb biomechanics in femoroacetabular impingement syndrome, asymptomatic cam morphology, and controls during bilateral and single-leg squatting

BACKGROUND: Femoroacetabular impingement syndrome (FAIS) is a movement-related disorder and causing hip and/or groin pain in young active adults. Movement patterns in individuals with FAIS may be modifiable through conservative management. Identifying biomechanical differences between cohorts with asymptomatic cam morphology (FAIM) and FAIS could reveal relevant treatment targets. This study compared lower limb kinematics and kinetics between FAIS, FAIM, and healthy controls during double- (DLS) and single-leg squats (SLS). METHODS: Whole-body motion and ground reaction forces were synchronously recorded during five DLS and five SLS. Joint angles, moments, and spatiotemporal parameters (mean squat velocity and maximum squat depth) were compared between groups using a one-way repeated measures ANOVA with statistical parametric mapping (SPM). RESULTS: During DLS, there were no differences in hip or knee kinematics, or hip, knee, or ankle moments. The FAIM group had less ankle dorsiflexion than controls during both descent and ascent (P < .01). During SLS, the FAIM group had greater hip flexion than the FAIS group (P < .01), and the FAIS group had greater external hip rotation than controls (P < .01) and a greater hip abduction moment than the FAIM group (P < .01). CONCLUSION: The greater demands of SLS may require those with FAIS to perform it differently to those without symptoms, regardless of the presence of cam morphology. Given all groups squatted to a similar depth, hip biomechanics - including flexion, rotation, and abduction moments - may be a more relevant target for rehabilitation.