The patellar tendon is attached to the thigh muscles (quadriceps) connected at the bottom of the kneecap (patella) and the top of the shinbone (tibia). It works to straighten the leg, and most often a tear in the patellar tendon is disabling and requires surgery. While diseases can cause tendon weakness leading to patellar tendon conditions, most often injury results from jumping, falling, or strong impact.