Causes, diagnosis and treatment of patellar tendon rupture


The patellar tendon is the structure that connects the patella (kneecap) to the tibia. A ligament is a structure that connects a bone to another bone, which is why some people call it a patellar ligament.

However, this structure actually connects the quadriceps muscle to the calf bone and the tendon connects the muscle to the bone, which is why the patellar tendon is a more common description.

The patellar tendon is an important part of the lower limb extensor mechanism. The extensor mechanism includes the quadriceps, the quadriceps tendon, the patella (kneecap), and the patella tendon. These structures work together to allow the knee to straighten and can do so with considerable force.

The extension mechanism is essential for normal functions, from walking and climbing stairs to sports activities such as running and kicking. Without a working extender mechanism, all of these actions can become difficult to perform.

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Symptoms of a patellar tendon tear

The typical person with a ruptured patellar tendon is a young male athlete. As more and more middle-aged people remain physically active, this trauma is becoming more common among the elderly .

The injury is usually associated with an awkward landing from a jump position, where the quadriceps muscle contracts, but the knee is forcefully extended. This is the so-called eccentric contraction, which puts tremendous stress on the tendons.

Injured athletes may feel clicking or popping and are generally unable to walk after injury.

Typical signs of a patellar tendon tear include:

  • Pain just below the kneecap.
  • Swelling and bruising on the front of the knee.
  • A defect or soft spot where the tendon should be tight.
  • Difficulty walking or playing sports.


Almost all patients with patellar tendon rupture have been found to have abnormal tendon tissue consistent with chronic tendinosis . The patellar tendon is usually injured in the tendon socket , where blood flow to the tissue is poor. and the tendon is the weakest.

Tendon ruptures can also occur in non-sports settings. These people usually have a cause for the weakened patellar tendon, such as a systemic disorder that weakens the tendons or recent knee surgery caused by a weakened tendon. Treatment is generally the same for athletes and non-athletes.


The diagnosis of patellar tendon rupture is usually evident on clinical examination. People who rupture the tendon will not be able to extend the knee against gravity and will not be able to perform the straight leg lift test . The examiner usually feels a tear in the tendon just below the kneecap.

An X-ray will be taken as a patellar fracture can cause similar symptoms and should be ruled out as a possible diagnosis. On x-rays, the patella is usually higher than the opposite knee because the quadriceps muscle lifts the patella and nothing is holding it in its normal position.

Although often not necessary, an MRI can be used to confirm the diagnosis and examine the knee for any other damage that may have occurred .

Watch out

A torn patellar tendon does not heal well on its own and, if left untreated, will lead to quadriceps weakness and difficulty with daily activities, including walking. Surgery to repair a torn tendon is relatively simple in concept, but can be difficult to perform.

The torn ends of the tendon must be sutured. The challenge is that it is important to restore proper tension to the tendon without putting too much strain or loosening.

Also, it can be difficult to get a good repair, especially if the tendon has detached directly from the bone. In these situations, the sutures used to repair the tendon can be attached directly through the bone .

Recovery and prognosis

Recovering from a patellar tendon tear is difficult and time consuming. One of the most important predictors of recovery is the time of surgery, and surgery if delayed for more than a few weeks can limit your ability to recover.

Early postoperative mobility, protected reinforcement, and avoidance of overload repairs are known to accelerate overall recovery. Even with these steps, there are at least three months left before returning to normal daily activities and four to six months before resuming sports .

Although most people heal completely after patellar tendon surgery, even with a successful recovery, long-term weakness can occur.

Athletes attempting to return to competitive sports may take a year or more to return to the functional level they were prior to injury. Guided exercise therapy can be helpful in giving athletes the opportunity to resume normal athletic activities.

Frequently asked questions

  • Not immediately. After a knee break, rest your knee and let it heal for several weeks. After the pain and swelling have subsided slightly, you can begin exercising to regain strength and range of motion in your knee.

  • For occasional pain during exercise, a patellar tendon strap can help. The strap supports the sore knee by keeping it level during physical activity. However, a strap is not the solution to a chronic knee problem. If you often have pain when running, see your doctor to find out the cause.

  • Resistance exercises can strengthen tendons, but to restore strength, stability, and range of motion, quadriceps exercises are necessary. Exercises that improve hip flexibility can also improve patellar tendon function.

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