What is the best exercise for VMO?
Lately, I have had few patients come in with chronic knee pain. Whether the diagnosis is patellafemoral pain syndrome, chrondomalcia patella, patellar tendonosis, or arthritis rehab exercises for the knee focus on the quadriceps. The VMO is a small and often ignored muscle of the quadricep complex. There are certain exercises that are given to target the VMO, but how good are they at really activating and isolating the muscle? I decided to look into the research to make sure I am giving my patients the best advice I possibly can. The source of this blog was based on a systematic review of 14 quality research papers looking into the activation of VMO during knee exercises.
Why is the VMO important?
Patellofemoral pain is often the cause of a muscle imbalance or timing problem between the muscles of the quadriceps; vastus medialis oblique (VMO) and vastus lateralis (VL). This imbalance can lead to patellar maltracking problems and improper biomechanics of the knee-joint leading to pain and dysfunction. In individuals with normal patellar tracking the vastus medialis oblique (VMO) fires first. When the VL fires before the VMO, the patella is more likely to track laterally. To correct the patellar tracking problem and strengthen the VMO, the patient should perform exercises that recruit more muscle fibers of the area. That is to say, an exercise that targets the weakened VMO over the predominant VL muscle.
What does the research say?
Several studies focus on exercises to recruit more VMO muscle fibers. Exercises described in the literature to activate the VMO are knee extensions, straight leg raises, wall squats, mini-squats, step-ups, lunges, leg press, balance and reach, open and closed kinetic chain exercises, and isometric muscle actions. There is still controversy in the literature as to which exercises recruit more muscle fibers of the VMO. Six studies found no difference in the VMO/VL ratio during various exercises. Yet another study concluded that medial hip rotation with knee extension recruited more muscle fibres of the VMO than the VL. Where as another similar study found hip position did not affect VMO fibres during knee extension. Two more studies concluded that squats recruit muscle fibers of the VMO, but hip position does not have an affect. Another study looked further into the squat exercise, comparing wide and narrow stance, and that agreed that it does recruit VMO muscle fibers regardless of the hip position. No studies have concluded one exercise or a group of exercises that isolates the VMO. Several exercises recruit muscle fibers of the VMO, but do not necessarily isolate the muscle in comparison to the other knee extensors.
So which exercise is the best?
There is still controversy in the literature as to which exercises recruit more muscle fibers of the VMO. There is no one best exercise. The use of biofeedback with exercise will increase the muscle activity of the VMO sooner, but a rehabilitation program without biofeedback will still increase the muscle activity of the VMO. Medial rotation of the hip during knee extension has shown to be more effective than lateral rotation, but during a wall slide or step-up hip placement did not affect the muscle fibers recruited of the VMO. The more difficult the activity, the more muscle fibers of the VMO are recruited (for example more muscle fibers are recruited while cutting than walking or when doing lateral step-up while holding weight than not holding weight).
Take home point
With patellafemoral pain the best way to rehab your knee is to strengthen the VMO is through general quadriceps exercises. Research has shown rehabilitation exercise to be effective. Trust the guidance of your health professional and challenge your body in a safe way to get the best results.
Source: VMO Exercises: A Systematic Review, Cassandra Offenberger. School of Physical Education at West Virginia University. 2008.