The extensor mechanism includes the muscles, bones, tendons, and ligaments above the knee joint, and allows individuals to straighten the leg. The extensor mechanism is made up of the quadriceps muscle, patella, quadriceps tendon, and the patellar tendon. The patellar tendon is the structure that connects the kneecap to the leg bone (tibia).

A patellar tendon tear, or quadriceps tendon tear is fairly common. In most cases, it is the result of a hard landing from a jump, such as in basketball or football, or from a fall. The tear occurs when the quadriceps muscle is contracting, while the knee is forced to bend.

Symptoms and Diagnosis

The symptoms of a tendon tear include: knee pain, knee weakness, and the inability to fully extend the knee. During a thorough physical examination, your physician will perform a straight leg test, along with a series of other assessments to look for a gap in the tendon, just above (quadriceps) or below (patellar tendon) the kneecap. A patella fracture can mirror symptoms of a tendon tear; an x-ray is usually recommended to rule out any fractures and other pathology. In most cases, your physician will require an MRI to confirm the diagnosis and to evaluate if any other damage has occurred to other ligaments in the knee.


A tendon tear is repaired with surgery. If a torn tendon is left untreated it will lead to weakness, stiffness, and muscle atrophy. Without surgery, walking may become quite difficult. During surgery, your physician will sew the ends of the torn tendon to secure them, and often reinforce the repair, by bringing sutures through the patella bone. While it is a straightforward surgery, it is important for the surgeon to assess and restore proper function back to the tendon while not making it too tight or too loose during the reconstruction process. Your physician should operate with extreme caution in these situations to ensure proper function is restored.


Following surgery to repair a torn tendon, recovery will be slow, yet progressive. Your physician will prescribe a thorough rehabilitation program that will include gradual range of motion exercises, and strengthening. It is important not to rush recovery with this type of injury, and thus a minimum of 3-4 months is recommended before returning to normal activities. A minimum of 6 months may be required until full sports activities can be resumed.