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

Context In the existing patellofemoral pain (PFP) literature, researchers often have assessed a single joint or each joint independently with limited evidence considering the relative contributions of the entire lower limb joint complex (ie, 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-legged squat and lunge between women with PFP and pain-free women. Design Cross-sectional study. Setting Laboratory. Patients or Other Participants A total of 34 women aged 18 to 40 years, including 17 participants with PFP (age = 26.1 ± 5.4 years, height = 165.3 ± 4.9 cm, mass = 66.2 ± 14.7 kg) and 17 pain-free participants (age = 27.2 ± 2.9 years, height = 162.7 ± 4.4 cm, mass = 59.0 ± 6.8 kg). 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 3 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 single-legged squat, women with PFP exhibited greater ankle-joint work ( P ≤ .04; Cohen d range, 0.74–0.87) and higher ankle-joint work contribution ( P ≤ .01; Cohen d = 0.91 or r = 0.48) in the sagittal plane for both energy absorption and generation compared with pain-free women. During the lunge, women with PFP displayed greater hip-, ankle-, and total joint work ( P ≤ .04; r range, 0.37–0.61) and higher hip-joint work contribution ( P ≤ .049; Cohen d range, 0.70–0.71) in the frontal plane for both energy absorption and generation compared with pain-free women. Conclusions Women with PFP may have different joint work redistribution strategies during functional tasks, characterized by increased work and work contributions from the proximal (hip) and distal (ankle) joints compared with pain-free women. Despite greater work by the proximal and distal joints, knee-joint work remained similar to that of pain-free women, resulting in a higher total work demand for the lower limb in women with PFP.