Timing differences of vastii muscles onset in patellofemoral pain syndrome patients following knee isokinetic extension training with maximum lateral tibial rotation

Patellofemoral pain syndrome (PFPS) is closely related to onset timing imbalance of vastus medialis oblique (VMO) and vastus lateralis (VL) muscles. The purpose of this study was to examine theeffect of selective isokinetic strengthening and quadriceps general strengthening exercises on onset timing of vastii muscles in patellofemoral pain syndrome patients.
Thirty-six women with PFPS (mean age 27.3±6.8 years) participated voluntarily in this study and were randomly placed in one of three groups included VMO selective isokinetic strengthening (VMO-SIS), quadriceps general strengthening (QGS) and control (CO) groups. Both exercises were performed for 8 weeks and VMO and VL onset timing were calculated using of an electromyography system. Data analysis were made by analyses of variance with repeated measures and Bonferroni tests.
Before interventions, there was no difference between groups (p>0.05) and in each groups, VMO onset time was more than that VL (p0.05). In QGS group, VL onset time value decreased (p=0.01) but, VMO onset time did not change (p>0.05). Also, VMO onset delay in VMO-SIS group decreased (p=0.002) but in QGS group increased (p=0.04).
The knee isokinetic extension training with maximum lateral tibial rotation and in close to knee full extension can be recommended as an appropriate therapeutic intervention for improving onset timing balance of medial and lateral vastii muscles in PFPS patients.