THE ROLE OF KNEES IN RUNNING

The knee is an anatomical part of our body called a joint. The knee is one of the most important joints of our body. It plays an essential role in movement related to carrying the body weight in horizontal (running and walking) and vertical (jumps) directions. In general, the importance of knee joints can’t be overestimated. In fact, it is so obvious, that there is no necessity to try to prove it.

But besides this obvious fact, there is also some other information about their function in running, which is very valuable and should be understood.

Traditionally, in the conventional paradigm of running, the knee function was understood as that of a joint producing the most power output for the forward propulsion, through, the so called, “push off” motion. This action is related with an active unbending or straightening of the knee of the support leg. Certainly, it is hard not to believe it, because what we see during the support time is very visual knee‘s flexing and extending motions, produced by visual and sensible muscular activity. A visual outcome of this activity is the forward movement of the body.

Well, you could say, what is here to discuss? Isn’t it clear that the activity of our knees makes us run faster? Another confirmation of this? No problem! Anatomically, the front side of the knee joint is surrounded by the most powerful knee extensor muscles of the quads, attached to one of the strongest (knee patella) tendon. At the rear, posterior side, the four strong muscles of the hamstring group are attached to the same joint.

OK, what is hidden from our sight now? Anatomical and mechanical facts seem to be so evident, it’s easy to make a conclusion that the knee functions as the most active joint in running. The answer to this would be “yes” and “no’. Yes, this joint is heavily involved anatomically and mechanically in running, and no, the function of this joint is not as obvious as we might think.

There are such facts as an extensor paradox and low vertical oscillation of the GCM of the body in running that reveal to us the real function of the knee in running, which is not related to active extension, but to flexion. Therefore during the support time the knee is just relatively fixed, and then flexed, when the support is over. The logic that follows is that we shouldn’t even think about knee extension, to say nothing about any efforts to do so.

Basically, the knee joint and related muscles and tendons surrounding it just accept the body weight load to provide for its fall forward and then flex to make easier the legs transfer under the body for the next support. So this function doesn’t have anything to do with any “activity” to propel the body weight forward.

It’s quite challenging to separate visual and functional activity of the knee in running and it requires a bit of abstraction from the “reality”, which we would “like” to see. Yes it is hard to reject what looks so obvious, but this is what actually helps you to save your knees in running.

Dr.Romanov