I have problems with my knees,just general stiffness-but one day I had to get down on my right knee and the pain was extreme,it wasn't necessarily in the knee but to the right side of the knee,it felt like the skin was splitting into,I look and the skin looked fine,so I don't know if it's the tendon or the muscle what ever it is,is very painful,in fact I can't get down on my knees any longer