Patellofemoral pain syndrome is commonly called runner’s knee, but it can occur in non-athletes, as well. It causes pain and irritation if your knee is bent for an extended period of time like when you’re walking or running, kneeling or sitting with crossed legs.
Your kneecap, called the patella, sits over your knee joint and connects with the lower end of your thighbone (femur). If your knee is moving the way it should, it rests in a groove on your thighbone, called the femoral groove, and slides up and down easily as you bend your knee.
Patellofemoral pain syndrome occurs when your kneecap is out of place and not lined up correctly on the femoral groove. It moves incorrectly and wears down the cartilage beneath it, causing dull, throbbing pain at the front and center of your knee.
Patellofemoral syndrome can be caused by a structural defect in your knee, direct trauma to the area or weak or tight knee muscles. The most common cause of this condition is overuse and activities that stress your kneecap—like when you run, jump, twist or participate in certain sports.