Sex-specific kinetic and kinematic indicators of medial tibiofemoral force during walking and running

Background Our aims were to (1) Evaluate sex-specific contributions of peak knee flexion moment (pKFM) and peak knee adduction moment (pKAM) in medial tibiofemoral joint (TFJ) force during walking and running; (2) identify kinematic variables to estimate peak medial TFJ force. Methods Eighty-seven runners participated (36 females, 51 males; age = 23.0 ± 3.8 years (1 standard deviation)). Kinematics and kinetics data were collected during treadmill walking (1.3 m/s) and running (3.0 ± 0.4 m/s). Peak medial TFJ contact force was estimated using a musculoskeletal model. Linear regression analyses were used to assess the contribution of pKFM, pKAM and kinematic indicators to estimated joint forces. Results During walking and running, pKAM and pKFM accounted for 74.9% and 64.5% of peak medial TFJ force variance (P < 0.001), respectively. Similar pKAM contribution was found between males and females during walking (51.8% vs. 47.9%), as opposed to running (50.4% vs. 26.8%). Kinematic indicators during walking were peak knee flexion and adduction angles, regardless of sex. During running, indicators were ankle dorsiflexion at foot strike and center of mass (COM) vertical displacement in females (R² = 0.364, P = 0.012), and peak knee abduction angle and step length in males (R² = 0.508, P = 0.019). Conclusion We conclude from these results that pKAM and pKFM make significant but potentially sex-specific contributions to peak medial TFJ force during walking and running. Clinically, peak medial TFJ force during walking can be estimated using peak knee flexion and adduction angles in both sexes. During running, ankle dorsiflexion at foot strike and COM oscillation are best indicators among females, while knee abduction and step length are best among males.