Effect of Posttrial Visual Feedback and Fatigue During Drop Landings on Patellofemoral Joint Stress in Healthy Female Adults.

Patellofemoral pain (PFP) is common in females. Patellofemoral joint stress (PFJS) may be important in the development of PFP. Ground reaction force (GRF) during landing activities may impact PFJS. Our purpose was to determine how healthy females alter their landing mechanics using visual posttrial feedback on their GRF and assess how PFJS changes. Seventeen participants performed a series of drop landings during 3 conditions: baseline, feedback, and postfatigue feedback. The fatigue protocol used repetitive jump squats. Quadriceps force was estimated through inverse-dynamics-based static optimization approach. Then, PFJS was calculated using a musculoskeletal model. Multivariate differences were shown across conditions (P = .01). Univariate tests revealed differences in PFJS (P = .014), knee range of motion (P = .001), and GRF (P = .005). There were no differences in quadriceps force (P = .125). PFJS and GRF decreased from baseline to feedback (P = .002, P = .007, respectively), while PFJS increased from feedback to postfatigue feedback (P = .03). Knee range of motion increased from baseline to feedback (P = .043), then decreased from feedback to postfatigue feedback (P < .001). Visual feedback of GRF may reduce PFJS, but may not effectively transfer to a fatigued state.