Running Gait Biomechanics Associated With Femoral Neck Bone Stress Injuries In Female Runners

PURPOSE: To compare running gait biomechanical profiles and clinical strength measures between female athletes with femoral neck bone stress injuries (BSI) and healthy controls. METHODS: We conducted a retrospective case-control study. Case group participants included symptomatic female runners (age 14-30 years) diagnosed with femoral neck BSI with magnetic resonance imaging (MRI) as part of routine clinical care. After medical clearance to return to running, femoral neck BSI patients, and age-matched healthy control participants underwent running gait analyses on a force plate treadmill. BSI case limbs were matched to healthy control limbs for analyses. Non-parametric Mann-Whitney U tests were used to compare demographics, strength, and continuous gait outcomes (spatiotemporal measures, kinetics), and Chi-square analyses were used to compare categorical gait outcomes between groups (footstrike type, pelvic drop, knee valgus, lower extremity midline crossover, foot landing position and pronation pattern α = .05). RESULTS: There were 18 females with a history of femoral neck BSI [age: 20.3 (1.0) yrs; BMI: 19.8 (0.6) kg/m2] and 19 female healthy controls [age: 18.3 (0.7) yrs, 21.5 (0.6) kg/m2]. The BSI group had significantly decreased hip abduction strength [1.66 (0.05) N/kg vs. 1.97 (0.03) N/kg; μ = 107, p < .05]. The BSI group demonstrated biomechanical profiles with higher proportions of limb cross-over (61.1% vs. 31.6%; X2 = 4.3, p = .04), knee valgus (61.1% vs. 31.6%; X2 = 11.5, p = .01), pelvic drop (88.9% vs. 47.3%; X2 = 8.3, p = .01), and landing position in supination with rapid pronation at midstance (100% vs. 63.2%; X^2 = 8.18, p = 0.004) compared to the healthy group. All other outcomes did not significantly differ between groups. CONCLUSION: Females with history of femoral neck BSI demonstrated characteristic running biomechanics profiles in the coronal plane that differed from their healthy counterparts. These findings support a possible contribution of biomechanical strain secondary to interrelated derangements of both proximal control and distal lower extremity running biomechanics in the development of femoral neck BSI. The observed decreased hip abduction strength among females with BSI may contribute to observed coronal plane motions throughout the kinetic chain during running gait.