Patellar & quadriceps tendon tears

The quadriceps muscles at the front of the thigh connect to the patella (kneecap) through the quadriceps tendon, which attaches just above the patella. Below the patella, the patellar tendon connects the patella to a bump on the front of the shin bone called the tibial tubercle.

Together, the quadriceps muscles, the quadriceps tendon, the patella, and the patellar tendon form the knee's extensor mechanism. This is the system that lets you actively straighten the knee, and it helps support you when you stand, walk, climb stairs, jump, and rise from a chair. When the mechanism is intact, the muscles pull through both tendons and the patella to extend the knee; when it is disrupted by a complete tear, that pull is interrupted and actively straightening the knee becomes difficult or impossible.

A tendon tear is different from the injuries described elsewhere on this site. The ACL is a ligament deep inside the knee that helps keep it stable during pivoting; the meniscus is a cushion that sits between the bones and absorbs load; and articular cartilage is the smooth coating on the ends of the bones. The quadriceps and patellar tendons are the cords that transmit the thigh muscles' pull to the patella and shin so the knee can straighten.

Because several knee problems can cause pain at the front of the knee, telling them apart matters. Not every ache or weakness at the front of the knee is a tendon tear — but a sudden loss of the ability to straighten the knee points specifically toward the extensor mechanism and deserves prompt evaluation.

Injuries to these tendons fall along a spectrum, and it is useful to separate a gradual, degenerative problem from a sudden tear:

• A complete tendon rupture: the tendon tears all the way through, so the extensor mechanism loses its continuity and active knee straightening is typically lost. This is the most important pattern to recognize.
• A partial tendon tear: some fibers tear but the tendon remains in continuity, and some ability to straighten the knee is often preserved.
• Tendinitis or tendinopathy: irritation or gradual degeneration of the tendon over time, which is different from an acute tear even though it can weaken the tendon.
• A patellar tendon tear, which typically occurs below the patella, between the kneecap and the shin.
• A quadriceps tendon tear, which typically occurs above the patella, between the kneecap and the thigh muscles.

Many complete tears happen when a strong contraction of the quadriceps muscle meets a sudden load — for example, stumbling, landing awkwardly, or catching a fall — sometimes on a tendon that was already weakened. The factors below are general and do not establish the cause in any individual person; several may be present, or none.

• A forceful contraction of the quadriceps while the knee is bending under load (an eccentric contraction)
• Landing from a jump or a sudden, unexpected load on the leg
• A direct blow to the front of the knee
• Preexisting tendon degeneration or prior tendon problems
• Prior surgery involving the knee or the tendon
• Some systemic health conditions and certain medications that can affect tendon health

The symptoms of a significant tear often come on suddenly, especially after a specific incident. They can include:

• Sudden pain at the front of the knee, sometimes with a tearing sensation
• Swelling or bruising
• A palpable gap in the tendon, above or below the kneecap
• Weakness, or difficulty straightening the knee or keeping it straight
• Difficulty performing a straight-leg raise — lifting the straightened leg against gravity
• A change in the position of the kneecap, which can sit higher or lower than usual
• Difficulty walking, or the knee giving way when bearing weight

One distinction guides how urgently an injury is evaluated: whether the extensor mechanism is intact or disrupted. It also helps to separate a true inability to straighten or raise the leg — which suggests the mechanism has lost continuity — from weakness that is mainly limited by pain, where the mechanism may still be intact. A patient in a lot of pain may be reluctant to move the knee even when the tendon is not completely torn.

A suspected complete rupture, or a new inability to actively straighten the knee or perform a straight-leg raise, warrants prompt orthopedic evaluation, because these injuries are generally addressed sooner rather than later. This does not require an emergency room in most cases, but it should not be left to see whether it improves on its own. If you are unsure, it is reasonable to be evaluated. This website is not monitored for emergencies — for a medical emergency, call 911.

Evaluation usually begins with the history of what happened and a physical examination. A central part of the exam is assessing active knee extension and the straight-leg raise, because losing the ability to straighten the knee is a hallmark of a disrupted extensor mechanism. The examiner also feels along the tendon for a gap and notes the position of the patella.

X-rays are used to look at the position of the patella, to check for a fracture, and to identify related bony findings. Ultrasound or MRI is used selectively — to characterize the tendon and the tear when the diagnosis is uncertain or when more detail would change the plan. Not every suspected tear requires an MRI; imaging is chosen to answer a specific question, and the findings are interpreted together with the history and examination.

Not every extensor-mechanism injury is treated with surgery. Selected partial tears in which active knee extension is preserved may sometimes be managed without an operation — typically with a period of immobilization or bracing followed by a progressive, staged rehabilitation program. Tendinitis and tendinopathy are also generally managed without repair surgery.

Whether a nonsurgical path is appropriate depends on the individual injury — how much of the tendon is torn, how much function is preserved, the quality of the tissue, how long ago the injury happened, any associated injuries, your overall health, and your goals. Part of nonsurgical care is following the knee over time so that treatment can be adjusted if the picture changes.

A complete rupture that disrupts active knee extension is commonly treated with surgical repair in patients who are medically appropriate for an operation, because the torn ends generally do not reconnect on their own well enough to restore the mechanism. Selected high-grade partial tears, or injuries with a persistent, function-limiting loss of extension, may also lead to an individualized discussion about surgery.

How soon a repair is considered, and what kind of procedure it involves, depends on the individual injury. In general, a fresh (acute) complete tear is repaired directly, whereas a tear that has been present for a long time — or one that is recurrent, neglected, or has failed a prior repair — can be more complex and may require a reconstruction or augmentation rather than a straightforward repair. Whether other injuries are present alongside the tendon tear also affects the plan. These options, and their trade-offs, are described on the treatment page.