Lower extremity kinematics in runners with patellofemoral pain during a prolonged run.

PURPOSE: Investigate lower extremity kinematics in runners with patellofemoral pain (PFP) syndrome during a prolonged run. METHODS: For this study, 20 runners with PFP and 20 uninjured controls performed a prolonged run on a treadmill at a self-selected pace. The run ended based on HR, perceived exertion, or level of knee pain. Kinematic data were analyzed at the beginning and at the end of the run. RESULTS: The PFP group demonstrated less peak knee flexion, peak hip adduction, eversion excursion, peak knee flexion velocity, peak hip adduction velocity, and peak hip internal rotation velocity compared with controls. A significant main effect for time indicated that increases in most kinematic variables occurred at the end of the run. Interestingly, five runners with PFP displayed atypical motions of knee valgus and eight displayed hip abduction during the first half of stance. CONCLUSIONS: The PFP group as a whole displayed less overall motion compared with controls. This may be indicative of a strategy aimed at limiting lower extremity movement to reduce pain. However, increases in joint motion occurred at the end of the run where pain levels were greatest. Three distinct PFP subgroups were noted, and each demonstrated unique kinematic mechanisms that may be associated with PFP. In the knee valgus subgroup, increased knee valgus and decreased peak motions were noted in other joints. In the hip abduction subgroup, less knee flexion and motion overall was noted. In the subgroup that displayed typical first half patterns (knee and hip adduction), increased hip internal rotation and decreased knee internal rotation were observed. These results suggest that several different kinematic mechanisms related to PFP may exist.