Vastus medialis obliquus and vastus lateralis activity in open and closed kinetic chain exercises in patients with patellofemoral pain syndrome: an electromyographic study.

OBJECTIVES

To evaluate the electromyographic activities of vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles in open and closed kinetic chain exercises in subjects with patellofemoral pain syndrome (PFPS).

DESIGN

Case-controlled study.

SETTING

Rehabilitation science center in a tertiary medical center.

PARTICIPANTS

Ten patients with bilateral knee pain diagnosed with PFPS and 10 healthy volunteers.

INTERVENTIONS

Subjects performed open kinetic chain exercise on an isokinetic dynamometer and closed kinetic chain exercise by squat-to-stand and stand-to-squat tasks. Surface electromyography was done for the VMO and VL muscles.

MAIN OUTCOME MEASURES

VMO/VL ratios were calculated after normalization of muscle activities.

RESULTS

The VMO/VL ratios of PFPS subjects were significantly lower than were those of unimpaired subjects during knee isokinetic closed kinetic chain exercises (p = .047). However, there was no statistical difference in VMO/VL ratio between subjects with and without PFPS during closed kinetic chain exercises (p = .623). Maximum VMO/VL ratio was obtained at 60 degrees knee flexion in closed kinetic chain exercise.

CONCLUSION

In closed kinetic chain exercises, more selective VMO activation can be obtained at 60 degrees knee flexion. Maximal VMO/VL ratio was observed at this knee flexion angle, and muscle contraction intensity was also greatest.