Active Seniors

Why do my knees cave in when I bend them?

A common technique error that we see as Exercise Physiologists is what is termed “valgus collapse” of the knees. Simply put, “valgus collapse” means that when bending the knees they move inwards towards each other and it often occurs when people squat down or transfer to or from a chair.

Why do my knees do this?

There are many explanations out there as to why this happens. The most common reason is that the muscles are weak and therefore allow the knee to collapse. At first it was the muscles in the thigh area that were blamed. Ideas then moved on from the thighs to the hip area and then the “glute” muscles then got the blame. However when we look at movement a bit more in depth we realise that there may be other factors to consider that influence this movement.

There are two important points to realise here. The first is that the body is under the conscious control of the brain. When you bend your knees to sit into a chair, the brain tells the body how to perform this movement. It does this by storing memories of movement patterns so that it becomes efficient at moving. It takes up to 200 muscles to take a single step, hence sending a signal to activate every single muscle during a movement would be a lot of unnecessary work for the brain. Instead the brain remembers the sequence of muscles that are required and stores this information. As they say practice makes perfect. Practice is what reinforces these sequences, and the more practice you do the less you have to “think” about them. Bearing this in mind, the movement of squatting or bending the knees to sit on a chair cannot easily be labeled simply as a muscle weakness. This is where point number 2 comes in.

Point number 2 is that the body acts to perform a task with the tools available (muscles and joints) and in response to its environment (balance requirements). This is often done without much thought as to what sequence would be best for the body long term. However simple changes can change the sequence of movement extremely quickly. If your knees cave in when you squat and an elastic band is placed around your knees to pull them even closer together, often your awareness of your body will auto-correct its fault and the knees will remain in good alignment instead of caving in.

This all comes down to increased awareness which is a driving factor for behavior. A true weakness of the hip muscles will not fix itself instantaneously like we see when the problem is our body awareness and sequencing.

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