Patellar and Quadriceps Tendon Ruptures

Patient information — Dr Christopher Spelman, Orthopaedic Surgeon

Overview

The extensor mechanism – the quadriceps muscle, its tendon, the kneecap (patella) and the patellar tendon – is what allows you to straighten the knee and hold it straight against load. A rupture of the quadriceps tendon (just above the kneecap) or the patellar tendon (just below it) breaks this mechanism, causing sudden pain and an inability to straighten the knee or take weight through it. The two injuries affect different groups: quadriceps tendon ruptures tend to occur in patients over 40 (and are more common with conditions such as diabetes, kidney disease, gout, or long-term steroid use, which weaken the tendon), while patellar tendon ruptures are more common in younger, active people, often during jumping sports and sometimes on a background of tendinopathy.

How it happens and symptoms

These injuries usually occur with a sudden, forceful load on a bent knee – a stumble, a fall, or landing awkwardly. Patients typically feel a pop or tearing sensation, cannot straighten the knee or perform a straight-leg raise, and often notice a gap above or below the kneecap. The kneecap may sit unusually high (with a patellar tendon rupture) or low (with a quadriceps tendon rupture).

Diagnosis

The diagnosis is often clear on examination – a palpable gap and an inability to hold the knee straight or lift the straight leg. X-rays may show the kneecap sitting too high or low, and ultrasound or MRI confirms the tear, shows whether it is partial or complete, and helps plan surgery. Distinguishing a complete tear (which needs surgery) from a partial tear where the patient can still straighten the knee (which may be managed without surgery) is the key decision.

Treatment

A complete rupture of either tendon is treated surgically, and early repair – ideally within the first week or two – gives the best result, because delay allows the tendon to shorten and scar, making repair harder. The torn tendon is reattached, commonly with strong sutures passed through bone tunnels in the kneecap or anchored with suture anchors, and the repair is sometimes reinforced (augmented). A chronic or neglected rupture may need a more complex reconstruction using graft tissue. Partial tears where the patient can still straighten the knee can often be managed without surgery in a brace.

Recovery

After surgery the knee is protected in a brace, generally in or near full extension initially. Rehabilitation has traditionally used a period of immobilisation (around six weeks) before progressively regaining bending, though many surgeons now use a carefully graduated, earlier-motion programme to reduce stiffness while protecting the repair. Restoring full straightening and quadriceps strength is the goal, and return to heavier activity and sport is later, guided by strength and healing.

Outcomes and complications

Most patients regain good function and strength after repair, and the re-rupture rate is low – in the order of 2%. Recognised complications include:

●      Extra bone formation within the tendon (heterotopic ossification) in around 7% of patients

●      Blood clots (deep vein thrombosis or pulmonary embolism) in around 2–3%

●      Wound problems and infection (uncommon)

●      Stiffness or a small loss of full straightening (an extension lag), and occasionally residual weakness

●      Patellar tendon repairs tend to have a somewhat higher failure rate than quadriceps tendon repairs, and chronic (delayed) repairs do less well than acute ones

Summary

A quadriceps or patellar tendon rupture is an acute injury that usually needs prompt surgical repair to restore the ability to straighten the knee. Results are generally good with early repair and structured rehabilitation, and re-rupture is uncommon. Because delay makes repair harder and outcomes less predictable, a knee that suddenly cannot be straightened after an injury should be assessed quickly.