Runner’s Knee (Patellofemoral Stress)
Runner’s knee or Patellofemoral Stress is when the kneecap (patella) rubs roughly against the end of the thighbone (femur) when the knee moves.
Runner’s knee may be caused by a structural defect, such as a kneecap located too high or too low in the knee joint, off-center insertion of the muscles into the kneecap, tight hamstrings, tight Achilles tendons, and weak thigh muscles – which normally help stabilize the knee. Weak thigh muscles are the most common treatable cause of runner’s knee; these weak muscles allow the kneecap to move sideways and rub against the thigh bone.
A second common treatable cause is rolling of the feet onto the outside (pronation) excessively when walking or running while the front thigh muscles (quadriceps) pull the kneecap outward. Together, these forces cause the kneecap to rub against the end of the thighbone.