Fixing the Flaws: Weak Vastus Medialis Oblique (VMO)

About the Author: Eric Cressey

The VMO is important not only in contributing to knee extension (specifically, terminal knee extension), but also enhancing stability via its role in preventing excessive lateral tracking of the patella. The vast majority of patellar tracking problems are related to tight iliotibial bands and lateral retinaculum and a weak VMO.

While considerable research has been devoted to finding a good “isolation” exercise for the VMO (at the expense of the overactive vastus lateralis), there has been little success on this front. However, anecdotally, many performance enhancement coaches have found that performing squats through a full range of motion will enhance knee stability, potentially through contributions from the VMO related to the position of greater knee flexion and increased involvement of the adductor magnus, a hip extensor.

Increased activation of the posterior chain may also be a contributing factor to this reduction in knee pain, as stronger hip musculature can take some of the load off of the knee stabilizers. As such, I make a point of including a significant amount of full range of motion squats and single-leg closed chain exercises (e.g. lunges, step-ups) year-round, and prioritize these movements even more in the early off-season for athletes (e.g. runners, hockey players) who do not get a large amount of knee-flexion in the closed-chain position in their regular sport participation.

Eric Cressey