Overview
The patellar tendon is the thick cord that runs from the bottom of the kneecap to the bump on the front of the shin (the tibial tubercle). It is the last component of the extensor mechanism: the quadriceps pulls on the kneecap, the kneecap pulls on the patellar tendon, and the tendon straightens the knee. When it ruptures, the leg cannot be straightened against gravity, which means it cannot climb a stair, get out of a chair or hold you up walking downhill.
A complete tear is therefore a surgical problem: the tendon ends retract, the kneecap rides up, and waiting improves nothing. The decisions are about timing and technique. Repair within the first two weeks is technically easier and heals better than a delayed repair, in which the tendon has shortened and scarred and often needs augmentation. Partial tears in which the patient can still lift the straight leg are the one group treated without surgery.
Common Symptoms
- A pop and sharp pain just below the kneecap during a jump, a landing or a stumble on a bent knee
- Inability to straighten the knee or lift the leg straight off a bed; the knee buckles when trying to stand
- A kneecap that sits visibly higher than the other side, with a gap you can feel below it
- Rapid swelling and bruising over the front of the knee
- In a partial tear, pain at the lower pole of the kneecap with weakness rather than complete loss of extension
The same mechanism in a patient over 40 more often tears the quadriceps tendon above the kneecap, where the gap is above the patella and the kneecap sits low rather than high. A kneecap that has dislocated produces similar swelling but extension is preserved once it has reduced. Months of pain at the lower pole in a jumping athlete without a sudden event is patellar tendinopathy (jumper's knee), treated with load management rather than surgery.
Causes & Risk Factors
The tendon fails under a sudden, violent contraction of the quadriceps against a bent knee: taking off or landing in basketball or volleyball, stumbling and catching oneself with the knee flexed, a fall on a ski slope, or a heavy squat. It is an injury of patients under 40, because in an older patient the quadriceps tendon usually fails first instead. Most tears occur in a tendon already degenerating at its attachment to the kneecap, which is why a history of jumper's knee is common. Corticosteroid injection into the tendon, fluoroquinolone antibiotics, diabetes, kidney disease and a previous bone–patellar tendon–bone ACL graft harvest all weaken it.
How It Is Diagnosed
The diagnosis is made on exam. Dr. O'Donnell asks the patient to lift the straight leg off the table; inability to do so, or an extensor lag in which the knee sags short of straight when held up, means the extensor mechanism is disrupted. A palpable gap below the kneecap and a high-riding patella confirm the level of the tear. Both knees are examined, because bilateral ruptures occur in patients with systemic tendon weakening.
Lateral X-rays show the kneecap sitting abnormally high (patella alta), sometimes with a fleck of bone pulled from its lower pole, and exclude a fracture of the kneecap itself. When the exam is clear, no other imaging is required before surgery. Ultrasound or MRI is ordered when the tear may be partial, when swelling makes the exam unreliable, or when the injury is weeks old and the degree of retraction will change the operation. Out-of-town patients can upload imaging through mymedicalimages.com.
Treatment Options
Non-operative care
A partial tear in a patient who can perform a straight-leg raise without lag, confirmed on MRI, is treated in a brace locked in extension for about 4 to 6 weeks with weight bearing as tolerated, followed by a progressive rehabilitation program. Extension strength is re-examined at each visit; a partial tear that loses extension has become complete and is repaired.
Patellar tendon repair
Every complete tear in a patient who wants to walk normally is repaired, and Dr. O'Donnell schedules acute ruptures within one to two weeks of injury. Through an incision over the front of the knee, the tendon end is freshened and secured to the lower pole of the kneecap with heavy sutures passed through bone tunnels or with suture anchors, and the torn retinaculum on either side is repaired so the kneecap tracks straight. Tears at the tibial tubercle or through the middle of the tendon are repaired end to end. A chronic tear, in which the quadriceps has retracted, requires the kneecap to be mobilized and the repair augmented with a hamstring graft or synthetic tape. The operation takes about an hour as an outpatient at Bayside Surgery Center under a nerve block plus general anesthesia, and is described on the quadriceps and patellar tendon repair page.
Recovery & What to Expect
The repaired tendon is protected from the pull of the quadriceps until it has healed to bone: the brace is locked straight for walking, active straightening is forbidden, and passive bending is progressed steadily so the knee does not stiffen. Dr. O'Donnell's protocol runs as follows.
| Phase | Timing | What happens |
|---|---|---|
| Protection | Weeks 0–6 | Brace locked in full extension for walking and sleeping; weight bearing as tolerated in the brace. Quad sets and straight-leg raises in the brace, patellar mobilizations, passive flexion to about 90° by week 6, full passive extension with heel props. No active or resisted knee extension. |
| Motion & early strength | Weeks 6–12 | Brace unlocked and weaned; crutches discontinued. Flexion to full, active extension begun, closed-chain strengthening in limited range, stationary bike. No deep loaded flexion. |
| Strengthening | Weeks 12–16 | Progressive closed-chain work, open-chain extension as cleared, low-impact conditioning, hip and core. Advance at full motion, no extensor lag and strength at least 70% of the other side. |
| Return to activity | Months 4–6 | Running and agility progression as cleared, sport-specific drills. Return to sport typically 5–6 months, surgeon-cleared on symmetric testing. |
Desk work is possible in the locked brace within one to two weeks; driving a right-knee patient waits until the brace is unlocked and the quadriceps can brake, usually 6 to 8 weeks; jumping sport at 5 to 6 months. The protocol is available as a PDF: patellar tendon repair.
Frequently Asked Questions
Can a patellar tendon tear heal without surgery?
A complete tear cannot. The tendon ends pull apart under the quadriceps, the kneecap rides up, and without a repair the leg never regains the ability to straighten against gravity. Partial tears in which you can still lift the straight leg without it sagging are the exception and are treated in a brace for 4 to 6 weeks, with the exam repeated to be sure the tear is not extending.
How soon does a torn patellar tendon need to be repaired?
Within one to two weeks of injury. In that window the tendon ends come together easily and the repair is strong. After several weeks the quadriceps shortens and scars, the kneecap becomes hard to bring down, and the repair usually needs a graft to bridge the gap. Same-week appointments are kept for acute injuries; call (305) 393-8810.
How long will I be in a brace after patellar tendon repair?
About 6 weeks locked straight for walking and sleeping, with weight bearing allowed in the brace from the start. Bending is advanced under the physical therapist's supervision during that time, reaching about 90° by week 6, and the brace is then unlocked and weaned over the following weeks as the quadriceps regains control.
When can I drive after patellar tendon surgery?
For a left knee with an automatic car, once you are off narcotic medication and can get in and out comfortably, often within two weeks. For a right knee, not until the brace is unlocked and the quadriceps can press the brake firmly, which is usually 6 to 8 weeks after surgery.
Will I get back to basketball or volleyball after a patellar tendon repair?
Most patients return to jumping sport at 5 to 6 months once strength is symmetric and functional testing is passed. The result depends on repair timing, on regaining full bend without stiffness, and on rebuilding quadriceps strength through the protocol. Re-rupture of a well-healed repair is uncommon.
This page is for general education and is not a substitute for a medical evaluation. Treatment recommendations depend on your individual diagnosis and goals. Kevin O'Donnell, MD sees patients from Coral Gables, Miami, Brickell, Pinecrest and Coconut Grove at 475 Biltmore Way, and out-of-town patients by telemedicine.