Vertical Ground Reaction Forces are Associated with Pain and Self-Reported Functional Status in Recreational Athletes with Patellofemoral Pain.

Individuals with patellofemoral pain (PFP) use different motor strategies during unipodal support in stair climbing activities, which may be assessed by vertical ground reaction force parameters. Thus, the aims of this study were to investigate possible differences in first peak, valley, second peak, and loading rate between recreational female athletes with PFP and pain-free athletes during stair climbing in order to determine the association and prediction capability between these parameters, pain level, and functional status in females with PFP. Thirty-one recreational female athletes with PFP and 31 pain-free recreational female athletes were evaluated with three-dimensional kinetics while performing stair climbing to obtain vertical ground reaction force parameters. A visual analog scale was used to evaluate the usual knee pain. The anterior knee pain scale was used to evaluate knee functional score. First peak and loading rate were associated with pain (r = .46, P = .008; r = .56, P = .001, respectively) and functional limitation (r = .31, P = .049; r = -.36, P = .032, respectively). Forced entry regression revealed the first peak was a significant predictor of pain (36.5%) and functional limitation (28.7%). Our findings suggest that rehabilitation strategies aimed at correcting altered vertical ground reaction force may improve usual knee pain level and self-reported knee function in females with PFP.