Jumper's knee is a clinical syndrome affecting adults, usually athletes, who are involved in sports that require repetitive violent contraction of the quadriceps muscle. The syndrome is characterized by chronic recurrent anterior knee pain and tenderness of the patellar tendon near its insertion to the patella. Initially the pain is present only after activity. Later, it may become persistent until finally the tendon ruptures.

An acute tendon tear usually presents with sudden pain, typically after a sports injury, and can be partial or complete. A discrete hypoechoic focus is visible within the tendon, representing intratendinous hematoma and edema.