Runner's knee (Patelofemoral pain syndrome), is a relatively common overuse injury associated with running. It is a generalized diagnosis, with symptoms of pain above and around the kneecap. The cause of runner's knee is typically a biomechanical instability of the hip, as opposed to an actual pathology of the knee. This is most easily diagnosed through slow motion analysis of the affected runner. What you will typically see in the mid-stance of the running gait is a dropping of the hip on the same side as the affected knee. This hip drop causes the femur (thigh bone) and tibia (shin bone) to internally rotated, thereby putting higher stresses on the knee. The increased rotational stress will affect the ability of the kneecap to track properly in the grove of the femur, ultimately causing pain. Additionally, the increased stress can cause injury to the patellar tendon, and other ligaments of the knee.