I probably shouldn't comment because I have never used them myself (though I just ordered some). But I would think you would be slightly more likely to tear a muscle using them due to the greater leverage it gives you which in turn allows you to lift heavier weights which would make your muscles more susceptible to tearing. How's that for a run-on sentence?
If im correct, they will most likely help protect your knee joint, NOT a muscle! I heard that they keep your knee in place and therefore it's not able to shift while your lifting.....