Quadriceps tendon tear: symptoms, diagnosis, surgery and recovery

The quadriceps is the group of four muscles at the front of the thigh. AAOS explains that these muscles meet just above the kneecap (patella) to form the quadriceps tendon, which attaches them to the kneecap. The kneecap is in turn attached to the shinbone by the patellar tendon. Together, the muscles, the quadriceps tendon and the patellar tendon form a pulley mechanism that straightens the knee.

This mechanism is called the extensor mechanism. It is what allows you to kick, stand up from a chair, climb stairs and keep the knee from buckling when you take weight on it. If the quadriceps tendon is torn, the pull of the thigh muscle is no longer transmitted to the shin.

AAOS describes two grades of injury. In a partial tear many fibres are damaged but the tendon is still in one piece, like a rope stretched so far that some fibres are frayed. In a complete tear the tendon is split into two pieces or separates completely from the bone, and the muscle is no longer anchored to the kneecap. Without that attachment, the knee cannot be straightened when the quadriceps contracts.

The NHS knee pain page lists a knee that is unstable, gives way when you try to stand, cannot be straightened and made a popping sound during the injury as a possible torn ligament, tendon or meniscus.

AAOS says that when a quadriceps tendon tears there is often a tearing or popping sensation, followed typically by pain and swelling, and that you may not be able to straighten your knee. A complete tear may also show up as a dip or divot just above the kneecap, because the muscle retracts and the kneecap may sit lower than usual.

• A tearing or popping sensation at the time of injury.

• Pain and swelling around the front of the knee.

• Bruising and tenderness above the kneecap.

• An indentation at the top of the kneecap where the tendon tore.

• Difficulty walking because the knee buckles or gives way.

• Being unable to straighten the knee, or to lift the straightened leg.

The NHS advises getting advice from NHS 111 now if your knee is very painful, you cannot move your knee or put any weight on it, it is badly swollen or has changed shape, or it locks or gives way. You can also go to an urgent treatment centre or minor injuries unit. A suspected complete rupture should be assessed quickly, because AAOS says early repair gives better results and that tendons often shorten if more than a month has passed.

The NHS also lists a very high temperature with redness or heat around the knee as a possible sign of infection that needs urgent advice.

AAOS explains that a quadriceps tear often occurs when there is a heavy load on the leg with the foot planted and the knee partly bent, for example an awkward landing from a jump. Falls, direct force to the front of the knee and cuts across the area can also cause tears.

Tendon weakness raises the chance of a tear, and AAOS lists several contributors: inflammation of the quadriceps tendon (tendinitis), chronic diseases that disrupt the blood supply to the tendon, steroid use, fluoroquinolone antibiotics, and prolonged periods off your feet. The chronic conditions it names include chronic kidney failure, hyperparathyroidism, gout, rheumatoid arthritis, lupus, diabetes, infection and metabolic disease.

This does not mean everyone taking one of these medicines or having one of these conditions is at risk. It means that if you have such a background and notice sudden knee pain with weakness, you should mention it to the clinician assessing you.

AAOS explains that a doctor will ask about your general health, your symptoms and previous knee injuries, then examine the knee and test how well you can extend it. The knee extension test, in which you try to straighten the knee against gravity, is used to help diagnose a quadriceps tendon tear. The examination can be painful, but it is important to separate a tear from other injuries.

Imaging may be used to confirm the diagnosis. AAOS says X-rays often show the kneecap sitting lower than normal when the tendon tears, and that complete tears can often be identified with X-rays alone. AAOS says an MRI is not typically necessary because the physical examination is usually telling, but it can show how much tendon is torn and where, rule out a similar injury, or distinguish a partial from a complete tear.

AAOS says most small, partial tears respond well to non-surgical treatment. This usually means a knee immobiliser or brace that holds the knee straight, crutches to avoid putting all the weight on the leg, and wearing the brace for 3 to 6 weeks. Once pain and swelling have settled, physical therapy restores strength and range of movement, with straight leg raises often central, and the brace is gradually unlocked.

Most complete tears need surgery. AAOS says the surgeon reattaches the tendon to the top of the kneecap, either by passing stitches through drill holes in the kneecap or by using small implants called suture anchors. It says most repairs are done on an outpatient basis, with either a spinal or general anaesthetic, and that some surgeons add extra protection with stitches or cables that may later be removed. If more than a month has passed, the tendon may have shortened and a tissue graft may be needed to lengthen it.

After repair, AAOS says the knee is usually protected in an immobiliser or hinged brace locked straight, you may be allowed to put weight on the leg with the brace and crutches, and the brace is then unlocked in steps so the knee can bend more over weeks. Strengthening exercises follow. About two weeks after surgery the skin stitches or staples are removed.

The rehabilitation plan is tailored to you, and the length depends on the type of tear, your repair, your general health and your needs. AAOS says complete recovery takes at least 4 months, most repairs are nearly healed at 6 months, and many people need 12 months to reach all their goals.

According to AAOS most people return to their previous occupations and activities, although slightly over half have some thigh weakness and soreness at the site of the tear. Possible complications include weakness, loss of knee movement, re-rupture, a change in kneecap position, infection, wound problems and blood clots. For athletes, return to sport depends on testing of leg strength, endurance and balance.

In the UK, surgery and rehabilitation are usually provided through NHS orthopaedic and physiotherapy services, and the NHS notes that in many areas you can refer yourself to community musculoskeletal services for physiotherapy.