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ABSTRACT. O'Sullivan, S.P., and C.A. Popelas. Activation of vastus medialis obliquus among individuals with patellofemoral pain syndrome. J. Strength Cond. Res. 19(2):302-304. 2005.The purpose of this study was to determine whether various positions of the lower extremity affect the muscle activity of the vastus medialis obliquus (VMO) differently during both open and closed kinetic chain exercise conditions among patients with patellofemoral pain syndrome (PFPS). Patients who presented with symptoms consistent with PFPS completed a series of open kinetic chain and closed kinetic chain exercises in which VMO activity was measured and compared. Statistical analysis revealed that there is less than a 0.001% (open kinetic chain) or 0.005% (closed kinetic chain) chance that all positions activate the VMO equally. In open kinetic exercise, maximum VMO activity was achieved with terminal knee extension with medial tibial rotation. During closed kinetic exercises, squats with external rotation were preferred for maximum VMO activation. Therefore, our results highlight the importance of including both the open and closed kinetic chain exercises into rehabilitation programs for patients with PFPS.
KEY WORDS, patellofemoral pain syndrome, knee pain, vastus medialis obliquus, muscle activity
INTRODUCTION
Patellofemoral pain syndrome (PFPS) is a prevalent knee disorder, especially among adolescents and young adults. The symptom most frequently reported is a diffuse peripatellar and retropatellar localized pain, typically provoked by ascending or descending stairs and squatting (5). The etiology of PFPS appears to be multifactorial, and many theories have been proposed. These include biomechanical, muscular, and overactivity theories (6). Each of the factors encompassed in these theories could potentially cause maltracking of the patella through the femoral trochlea, resulting in increased pain and decreased function (5).
A review of the literature yields few trials regarding the treatment of PFPS. Despite the lack of evidence, quadriceps strengthening is most commonly recommended as the primary treatment due to the significant role these muscles play during patellar movement (6). The quadriceps muscles include the vastus medialis, vastus medialis obliquus (VMO), vastus intermedius, vastus Iateralis, and rectus femoris (6). Current conservative treatment focuses on quadriceps strengthening, with emphasis on the VMO (1, 3). The VMO is of primary importance, because weakness of this muscle allows the patella to track too far laterally, which increases patellofemoral joint stress and subsequent articular cartilage wear...