Ok first not to be picky but there are no muscles in the knee. The knee is a joint. There is bone, ligaments and cartlidge but no muscles. You may have pulled a leg muscle or sprained a ligament in the knee. Where on the knee does it hurt? right side, left side, front, back? All of these are basic questions that need to be known in order to guess what you have done. There is a lot that goes into selecting a knee brace depending on what is wrong. Depending on what you did a knee brace may not be the answer and may be a waste of money.