Relationships between lower extremity kinematics and impact load or joint work contribution during landing in individuals with and without patellofemoral pain.

Higher lower limb impact load during landing in individuals with patellofemoral pain (PFP) is associated with increased risk of musculoskeletal injuries. This study aimed to investigate differences in landing kinematics, impact load and joint work contribution between individuals with and without PFP, and to identify relationships between kinematics and kinetics variables. Twenty-three PFP patients and nineteen healthy controls performed drop jump tests. Joint angles, peak vertical ground reaction force (PvGRF), average loading rate and joint work contribution were evaluated. Independent t-tests and Mann-Whitney U tests were used to compare the differences between groups. Pearson and Spearman correlations were used to examine relationships between kinematics and kinetics variables. The results demonstrated that the PFP group exhibited significantly greater ankle plantarflexion angle at initial contact, less knee flexion and ankle dorsiflexion angles at peak knee flexion angle, greater PvGRF and ankle joint work contribution than the control group (p ≤ 0.045). In the PFP group, no significant associations were found between kinematics and PvGRF (p ≥ 0.059), and the ankle plantarflexion angle at initial contact (r = 0.703) and peak knee flexion angle (r = -0.470) were correlated with ankle joint work contribution. These results suggest individuals with PFP exhibited impaired ability to absorb impact and greater reliance on the ankle for impact absorption. Rehabilitation programs for individuals with PFP should not only focus on the knee joint function but also on optimizing ankle joint motor control, as well as soft-landing techniques and balanced load distribution across the lower limb kinetic chain.