I think the knee circle warm up is kind of pointless. If done slowly and gently enough, they probably aren't going to cause damage. However, they are putting your entire lower limb in a very mechanically disadvantaged and potentially harmful position at both sideways extremes, if the legs were to assume a serious load in that position or if stronger lateral presssure were applied. As such, it seems like 'dry run' practicing for getting into a postion that you don't want to be in in the first place, so why bother?
If you look at what's going on in the lower limb, the side-to-side movement is actually mostly being accomplished via movement at the hips and ankles anyway. "Knee circles" is basically a misnomer. Having the knee in that position under heavy stress is definitely asking for an injury. Under load, you want the knee, ankle, and hip held stable in the same vertical plane, so why not warm up that way and simultaneously practice sound movement mechanics instead of unsound ones? As such, free squats and lunges and variants are much better lower limb warmups.
My bottom line: the knee circle probably isn't that dangerous, but is a silly and nearly pointless exercise.
Incidentally, the prescription of not bending the knee more than 90 degrees is only for people with certain injury-induced movement restrictions. There is no reason why healthy knees can't bend all the way until butt hits ankles under load provided the flexibility is there and the movement pattern is sound. The same goes for the myth that knees shouldn't extend past the toes when lunging squatting. I can see the rationale behind eschewing frog jumps though: the movement mechanics and the extreme ROM at speed make it an advanced plyometric movement at best, and a hazard for most at worst.
Last edited by Kevin Wilbanks : 05-21-2003 at 05:20 PM.