Posted by: PFB
Q. I have heard that leg extensions are damaging to the knees. Could you explain the reason(s) for that?
A. "Damaging" is a vague term. Strength training is "damaging" to the muscles, but with proper planning and rest, the body overcomes the "damages" and becomes bigger and stronger. The real question is, how damaging are knee extensions and is there a better alternative? Leg Extensions cause a shearing force at the kneecap. Basically, "shearing" is a force that is parallel to the contacting surfaces that could degrade the cartilage and protective tissues inside the knee structure. Regardless of this fact, I'm not a big fan of knee extensions because they are so "non-functional" in the real world. How often are you extending the lower leg while the hip joint is fixed? I know many "bone-head" physical therapists who still prescribe them for knee rehabilitation. If they only knew! Granted, there may be a "neurological issue" which would necessitate contraction of only the quads to retrain the nervous system. But this is obviously a rare situation. Given all the possible variations of step-ups, split squats, one-legged squats and full squats, I see no reason to perform leg extensions.