Joint Coupling Variability and Knee Pain During Running

Introduction The knee and subtalar joint actions are related by the internal/external rotation motion of the tibia during the support phase of running. It has been suggested that maximum knee flexion should occur at the same time as maximum subtalar eversion during which time the tibia undergoes internal rotation (Bates et al., 1978). Asynchronous timing between knee joint flexion and ankle joint eversion maxima has been related to knee pain in runners (Hamill et al., 1992; McClay and Manal, 1997). Hamill et al. (1999) suggested using a dynamical system analysis in the investigation of lower extremity joint couplings. Using preliminary data, they assessed the use of the continuous relative phase (CRP) and the variability of the CRP of various lower extremity couplings in subjects with knee pain and those with no knee pain. They suggested that greater variability, indicating a much looser coupling between lower extremity joint actions, would be the norm in healthy individuals while less variability, indicating a much tighter coupling, would be evident in individuals with knee pain. The purpose of this study was, therefore, to assess joint coupling variability from a dynamical systems perspective in individuals with patellofemoral pain (PFP) and those without a history of knee pain.