The effect of isokinetic exercise on symptoms, functional status and EMG activation onset time of the vastus medialis oblique and vastus lateralis in female patients with patellofemoral pain syndrome

The aim of this study was to evaluate VMO and VL EMG activation onset times (AOT) during isometric contractions at various degrees of knee flexion and to explore the effects of a 6-w isokinetic exercises program on pain, quality of life, muscle strength and, if observed, on the difference in AOT, in patients with patellofemoral pain syndrome (PFPS). Twenty two female patients suffering from anterior knee pain and diagnosed with PFPS were recruited. The main outcome measures consisted of AOT and maximal isometric contraction of VMO and VL muscle and Medical Outcomes Study (SF36) and VAS scores. Compared to control knees, pre-exercise measurements revealed significant delay only in VMO at knee flexion angles of 15°, 30°, 45°. Post-exercise measurements showed improvement in the delay at 15°, 30°, 45° and also in the other pain, health quality and muscle strength measurements. In conclusion; VMO is activated later than VL in PFPS patients while exercise results in improvements in both symptoms and delay in VMO.