The dynamic stability of the patella in persons with patellofemoral pain

Abstract

Objective To analyze the activity of the vastus medialis (VM) and vastus lateralis (VL) muscles in the dynamic stabilization of the patella in patients with patellofemoral pain (PFPS) using standard surface electromyographic (sEMG) tests.Methods This comparative study involved 7 patients with PFPS (13 knees) and 10 healthy subjects (20 knees).They performed weight-bearing squat movements,and sEMG was employed to measure the mean amplitude and the time before peak (TBP) of their VM and VL muscles.Results There was no significant difference between the two groups in the ratio of the mean amplitudes of the VM and VL muscles.However,the ratio in both groups in squatting was significantly higher than when simply standing.In the PFPS group the average TBP delay of the VM relative to the TBP of the VL was significantly longer than in the control group during squat movements.Conclusions The delay in the TBP of the VM relative to the VL during squat movements could serve as a standardized test for assessing treatment effect in patients with local factor PFPS. Key words: Surface electromyography; Patellofemoral pain ; Knee pain ; Vastus medialis; Vastus lateralis