What does the evidence say about VMO strengthening?
I am sure many of you have come across a clinician or trainer who has stressed the importance of strengthening your Vastus Medialis Obliquus, or more commonly referred to as the VMO. Your first question should be, “What is so important about the VMO?”
Well, it has been hypothesized that an imbalance between the vastus medialis obliquus and the vastus lateralis (VL) muscle may be a key factor in why individuals develop patellofemoral pain syndrome. Atrophy and/or inhibition of the VMO may lead to patellar instability due to the imbalance of strength between the VMO and VL, leading to an increased lateral pull on the patella. Due to these suggested claims, it has often been proposed that individuals need to specifically train their VMO in order to have proper patellar tracking. While this may sound good in theory, what does the evidence have to say about strengthening the VMO?
A systematic review by Smith et al. in 2009 (1) looked into the question, “Can the vastus medialis obliquus (VMO) be preferentially activated?” They analyzed 20 studies that used EMG to record the VMO activity while patients either co-contracted lower extremity muscle groups or altered lower limb position (these are the two proposed ways to activate the VMO specifically). The review suggested that the VMO could not be preferentially activated by the methods used in the analyzed studies. The authors recommended that clinicians should not focus on VMO strengthening, but instead focus on general quadriceps training.
A RCT by Bennell et al. in 2010 (2) compared the effects of VMO retraining vs. general quadriceps strengthening. They determined that both exercise programs equally improved motor control, strength, pain, function, and quality of life in the short term in patients with PFPS. Another study, a RCT by Smith et al. in 2015 (3), also compared VMO strengthening vs general quadriceps strengthening, except their patient population was individuals who experienced a first time patellar dislocation. Similar to the findings of the Bennell et al. study, they found no clinically significant difference in functional outcome and activity levels between the two groups. Both the Bennell study and the Smith study used different strengthening protocols, yet found similar results.
While improper patellar tracking and anterior knee pain may be due to atrophy or inhibition of the VMO, the evidence does not support strengthening programs attempting to isolate the VMO. A quick recap of the evidence:
Instead of focusing on crazy exercises that involve cocontracted lower extremity muscles or altered limb positions, spend your time on basic, functional, quadriceps strengthening exercises → squats, lunges, step-ups, step-downs, etc. In addition, you are doing your client (or yourself) a disservice if you are only focusing on the muscles on the anterior thigh (quads). It is important to analyze what is going on at the hip and ankle, as well as look at hamstring strength, overall lower extremity flexibility, and body mechanics. Remember – always treat impairment based!
1. Smith TO, Bowyer D, Dixon J, Stephenson R, Chester R, Donell ST. "Can vastus medialis oblique be preferentially activated? A systematic review of electromyographic studies." Physiother Theory Pract. 2009 Feb
2. Smith TO, Chester R, Cross J, Hunt N, Clark A, Donell ST. “Rehabilitation following first-time patellar dislocation: A randomised controlled trial of purported vastus medialis obliquus muscle versus general quadriceps strengthening exercises.” Knee 2015; 22(4):313-20.
3. Bennell K., Duncan M., Cowan S., McConnell J., Hodges P., and Crossley K.: Effects of vastus medialis oblique retraining versus general quadriceps strengthening on vasti onset. Med Sci Sport Exerc 2010; 42: pp. 856-864