Physical therapy alters recruitment of the vasti in patellofemoral pain syndrome

Abstract

To investigate the effect of physical therapy treatment on the timing of electromyographic (EMG) activity of the vasti in individuals with patellofemoral pain syndrome (PFPS). Sixty-five (42 female, 23 male) participants aged 40 yr or less (29.2 ± 7.8 yr) diagnosed with PFPS. Participants were randomly allocated into physical therapy treatment (McConnell-based) or placebo groups. Treatment programs were standardized and consisted of six-treatment sessions over 6 wk. Vastus medialis oblique (VMO) and vastus lateralis (VL) EMG activity was recorded with surface electrodes during a stair-stepping task and onsets of EMG activity were measured pre- and post-treatment. Before treatment, the EMG onset of VL occurred before that of VMO in both participant groups. After physical therapy intervention, there was a reduction in symptoms, and this improvement was associated with a significant change in the time of onset of VMO EMG compared with that of VL in both phases of the stair-stepping task. After physical therapy treatment, the onset of VMO preceded VL in the eccentric phase and occurred at the same time in the concentric phase of the stair-stepping task. There was no change in time of EMG onset in the placebo group. This study demonstrates that a “McConnell”-based physical therapy treatment regime for PFPS alters the motor control of VMO relative to VL in a functional task and this is associated with a positive clinical outcome.