Knee pain is thought to be primarily associated with specific quadriceps muscle weakness or fatigue, especially in the vastus medialis obliquus (VMO).
It is known that fatigue can be caused by many different mechanisms, ranging from the accumulation of metabolites within muscle fibers to the generation of an inadequate motor command in the motor cortex.
Characteristics of the vastus medialis, including its angle of insertion, correlate with presence of knee joint pain (patellofemoral pain syndrome). However, this syndrome is complex and definitive evidence of causality has not yet been published.
