Lower Extremity Energetic Redistribution During Functional Tasks in Patellofemoral Pain: Proximal, Local, and Distal Contributions

ABSTRACT Context: Existing patellofemoral pain (PFP) literature has often assessed a single joint or each joint independently, with limited evidence considering the relative contributions of the entire lower limb joint complex (i.e., hip-knee-ankle). Objective: To compare joint work and work contributions of the hip, knee, and ankle in the sagittal and frontal planes during a single-leg squat (SLS) and lunge between females with PFP and pain-free females. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: Thirty-four females (17 with PFP and 17 pain-free) aged 18– 40 years. Main Outcome Measure(s): Joint work was computed by integrating the negative (energy absorption) or positive (energy generation) regions of the joint power curve. Joint work contribution was determined as a percentage of the sum of all three lower limb joints (hip, knee, and ankle) during energy absorption and energy generation. Group comparisons were performed using independent t-tests or Mann-Whitney U tests, with Cohen d or Wilcoxon r effect sizes, respectively. Results: During the SLS, females with PFP exhibited greater ankle joint work (P≤.038; d=0.74-0.87) and higher ankle joint work contribution (P≤.012; d=0.91 or r=0.48) in the sagittal plane for both energy absorption and generation compared to pain-free females. r=0.37-0.61) and higher hip joint work contribution (P≤.049; d=0.70-0.71) in the frontal plane for both energy absorption and generation compared to pain-free females. Conclusions: Females with PFP may have different joint work redistribution strategies during functional tasks, characterized by increased work and work contributions from proximal (hip) and/or distal (ankle) joints compared to pain-free females. Despite greater work by the proximal and distal joints, knee joint work remained similar to that of pain-free females, resulting in a higher total work demand for the lower limb in females with PFP.