Morphometric analysis of vastus medialis oblique muscle and its influence on anterior knee pain.

Healthy knees require full range squatting movements. Vastus medialis (VM) muscle regulates and adjusts the extensor apparatus that influences the patellofemoral function. This work was designed to investigate the anatomy and morphometry of vastus medialis oblique (VMO) muscle by widely used imaging techniques and investigate how VMO muscle participates in anterior knee pain. Ten dissected cadaveric specimens were examined, focusing on fiber orientations, origin, insertions and nerve supply of VMO muscle. Magnetic resonance imaging and ultrasound of VMO muscle were recorded. Anatomical cross-sectional areas of VMO muscle were determined in painless and painful knees and statistically analyzed. In cadaveric specimens, there was distinct separation between VM longus and VMO (change in fiber angle or fibro-fascial plane). VMO inserted directly into the medial proximal margin of the patella, capsule of the knee joint and continuous with the patellar tendon. Separate branch of femoral nerve run along the anteromedial border of the muscle. Anatomical cross-sectional area was significantly decreased in painful knee by -17.2%±11.0% at lower end of shaft of femur, -21.1%±6.0% at upper border of patella, -36.7%±11.0% at mid-patellar level. VMO is distinct muscle within quadriceps femoris group. VMO muscle would track the patella medially and participate in last phase of knee extension. Assessment of the VMO muscle anatomical cross-sectional area by ultrasonography may constitute promising and reliable tool to evaluate patellofemoral pain syndrome staging.