The patella tendon is one of the largest tendons in the human body, hence ruptures of this structure are extremely rare. Usually high-energy trauma such as a dashboard injury or a fall onto the tendon is often required to cause complete disruption. However sudden quadriceps muscle contraction or acute knee flexion when jumping from a height has also been reported as possible mechanisms of injury. Patients with previous tendon damage or chronic tendon inflammation are more likely to be affected. Certain medical conditions like endocrinological disorders or diabetes as well as prolonged steroid intake may change the mechanical qualities of the tendon and have been associated with acute tendon ruptures through relatively minor trauma. Performance enhancing drugs and anabolica may have a similar effect and should always be considered as possible causes especially in highly trained individuals.

Once the tendon is torn the patella is usually pulled proximally by the quadriceps muscle. A lateral radiograph will demonstrate a high standing patella (patella alta). The clinician may detect a noticeable dimple just above the tibial tuberosity, although in acute swelling this is not always apparent. The key assessment should focus on comparative radiographs and the patient's inability to perform a straight leg raise.

The treatment is based on tendon repair or refixation, which is usually achieved by using a wire cerclage secured with a trans-cortical screw. The patient may be immobilised temporarily in a hinged brace locked in full extension, but passive mobilisation should be encourage within a few weeks post surgery. Stiffness, reduction in range of motion and quadriceps weakness as well as anterior knee pain are common and require intensive physiotherapy. If patients who have undergone patella tendon repair develop widespread pain, discomfort, tenderness and skin changes, Reflex Sympathetic Dystrophy (RSD) or Complex Regional Pain Syndrome should be considered as possible complications.