Patellar tendon tears can be either partial or complete.
PARTIAL TEARS: Many tears do not completely disrupt the soft tissue. This is similar to a rope stretched so far that some of the fibers are torn, but the rope is still in one piece.
COMPLETE TEARS: A complete tear will disrupt the soft tissue into two pieces.
The patellar tendon often tears where it attaches to the kneecap and can break a piece of the bone as it tears. When the patellar tendon is completely torn, the tendon is separated from the kneecap. Without this attachment, you cannot straighten your knee.
When a tear is caused by a medical condition — like tendonitis — the tendon usually tears in the middle.