Rearfoot and knee coupling over a prolonged run in runners with patellofemoral pain syndrome
© Davis and Dierks; licensee BioMed Central Ltd. 2008
Published: 26 September 2008
Patellofemoral pain syndrome (PFPS) is common in runners and is often related to excessive rearfoot eversion. Increased eversion is known to be associated with increased knee flexion, internal rotation, and reduced adduction . Therefore, our purpose was to investigate coupling between the foot and knee in runners with PFPS. We hypothesized that the PFPS group would display larger coupling angles at baseline, due to relatively greater eversion. We also expected that these angles would increase to a greater degree in the PFPS group at the end of a prolonged run.
20 runners (18–40 yrs) with PFPS and 20 controls (CON) participated in a prolonged treadmill run averaging 30–45 min. The run was stopped when preset criteria of heart rate, perceived exertion or knee pain were reached. 3D kinematic data were collected at the beginning and end of the run. A vector coding method  was used to assess the following joint couplings: rearfoot eversion (EV) with knee flexion (KF), adduction (KADD), and internal rotation (KIR). Coupling angles of 45° indicate equal joint excursions. Increasing values indicate more eversion, decreasing values indicate more knee motion. Values were averaged over the first half of stance: Period 1 (initial loading): footstrike to vertical impact peak (VIP) and Period 2 (maximal loading): VIP to vertical propulsive peak. A 2-factor ANOVA (group by time) was used (p = 0.05).
Coupling angles are lower at initial loading in the PFPS group. During maximal loading, coupling is generally similar between groups. Finally, both groups increased their coupling angles over the course of the prolonged run.
This article is published under license to BioMed Central Ltd.