Patellar tendinitis is a common injury of the patellar tendon. The patellar tendon works with the muscles at the front of the thigh to straighten the knee. Also known as jumper's knee, it often happens in athletes whose sports involve a lot of jumping.

Pain is the first symptom of patellar tendinitis. The pain most often is between the kneecap and where the tendon joins the shinbone. Over time, the pain can worsen and affect daily activities such as stair climbing.

Treatment often begins with limiting activities that cause the pain and physical therapy.