Terminal knee extensions are used to strengthen the quadriceps. It is believed that this exercise helps runners knee. Runner's knee is when the patella (kneecap) rubs against the end of the femur (thigh bone) as the knee moves. The terminal knee extension exercise strengthens the (VMO) vastus medialis oblique muscle, which is primarily charged with keeping the patella in its proper place. For increased comfort, place a towel behind the knee before tightening the elastic band.