Patellofemoral (PF) pain syndrome is pain in the front of the knee and around the patella. It is sometimes called “Runner’s Knee” or “Jumper’s Knee” because it is common in people who participate in sports that involve running and jumping. Pain often increases when you run or play sports, squat, walk up hills or stairs, and especially with walking down hills or stairs. In addition, sitting with the knee flexed for prolonged periods of time can increase PF pain. Persistent swelling is often not present until the injury has progressed significantly.