Chronic knee pain is an issue many of our clients come to us to help address. Based on our experience, and scientifically backed by a large number of studies, we know that stronger quads equals less knee pain . But what if we could get more specific with that knowledge? What if we could help our clients know exactly what needs strengthening to have the greatest impact on knee pain, osteoarthritis, and potential surgeries down the road? Thankfully, research has come to the rescue! This research confirms what our experience based on for years of on the floor training has lead us to believe, that the Vastus Medialis Obliquus, or VMO, is the king when it comes to knee health.
As a refresher, the VMO is that teardrop shaped muscle on the inside of your thigh. Although it is part of the quadriceps muscle group which straightens your knee, the fiber orientation of the VMO means that it acts as more of a powerful stabilizer and less of a knee extender.
Starting on the floor, and “mastering” this level of difficulty for weeks and even months will help to serve a solid foundation of strength in not only the muscles surrounding your knees, but more importantly the connective tissues supporting your knees to help protect you from future injuries.
It used to be passed around as common knowledge that the VMO couldn’t be isolated in training. Past studies have experimented with various squat types and hip positions to isolate the VMO but to no avail. What all these studies had in common was that they only trained knee extension from a maximum of 90 degrees knee bend.
Interestingly, research in 2016 appears to suggest that when a knee is taken to around 140 degrees of flexion, the VMO is proportionally activated to a greater degree than the vastus lateralis, the force of which the VMO works to counteract. So with the old VMO folklore out of the way, let’s dig into why we all need to make VMO-specific training a major focus of our lower body strength training.
A Stronger VMO is more protective of knee cartilage
One of the hallmarks of knee osteroarthritis is joint space narrowing, which is the result of the slow (and sometimes fast) degradation of the cartilage in your knee over time. This begs the question: what causes the breakdown of the cartilage in the knee? The easy assumption (and indeed past advice) is that excessive load on the knee joint is likely the cause and that things like heavy squatting should be avoided as they put lots of pressure on the knee and all of its components.
This assumption is directionally not completely wrong, it just misses the mark on the causes and what can be done to address joint space narrowing. While there are many factors that can contribute to this shrinking of joint space, it turns out that one of the highly modifiable ones is quadriceps muscle weakness. As previously noted, studies have shown that quad strength and knee health have a positive relationship, meaning the stronger your quads, the healthier your knees. Pretty simple, right? But why?
This positive relationship exists simply because a stronger quad will help control the speed at which your knee experiences what are called “impulsive forces” (or sudden large impacts) such as when your heel strikes the ground when walking or running. Interestingly, it is the rate at which the impulse happens that is the driver of knee cartilage damage, not the amount of the load. Put simply: control the load, control the damage.
Recent research has gone a step further to identify the VMO as a primary player in helping to protect medial knee cartilage volume, and therefore joint space as well. This study showed that in patients with knee OA, those who increased the size of their VMOs over a two year period had significantly less knee pain and cartilage loss than those whose VMOs had gotten smaller. This same study also found that this increased VMO size also reduced the risk of knee replacement over a four year period.
A Stronger VMO improves patellar tracking.
Though this article is primarily about the VMO, we can’t forget about it’s counterpart the Vastus Lateralis, which is the largest of the four quadriceps muscles. This big muscle, located on the outside of your thigh, is an important extender and stabilizer of the knee.
In the presence of knee pain, the vastus lateralis becomes more dominant and, as its name suggests, it imparts a lateral, or outwardly-directed pull on the knee cap. This pull is greater than the medial-directed pull of the VMO.
The net result?
More pressure on the lateral cartilage of the knee, and more knee pain over time. Once again, the solution here is simple: restore VMO strength to improve patellar tracking.
Great, but HOW?
As discussed above, we’ve put to rest the notion that you can’t selectively train the VMO. Strength trainers have known for decades that this wasn’t true, it just took research years to have the courage to squat low enough to “discover” the truth. In order to target that teardrop shaped muscle on the inside of your thigh, you simply need to bend your knee to around 140 degrees and apply load. Put another way — just squat deep. Get as low as you can safely go without pain.
There’s quite a few options for getting into VMO territory on your squats. Pick the one that works best for you and build it into your weekly routine. I suggest taking all of your squats to depth if possible.
Of course not everybody will be able to achieve full knee flexion right away (or perhaps ever — if they’ve had a knee replacement), and that’s okay.
We prefer to start knee pain clients off with exercises such as Assisted Squats, Reverse Step-ups, Patrick Step-ups, and eventually Poliquin Step-ups (as seen in videos above).
We prioritize moving pain free, reducing the loading, reducing range of motion, and encouraging what we call “tendon bathing”. We want to get as much blood into the tendons and connective tissues to promote healing and move towards more pain free movement.