Torn patellar tendon: A rare but serious knee injury

What is does the patellar tendon do?

The patellar tendon connects the kneecap (patella) to the shin bone (tibia). Strictly speaking, the patellar tendon is not actually a tendon, but a ligament – and as such is sometimes called the patellar ligament. Ligaments connect bones to bones; tendons connect bones to muscles. The patellar tendon transmits the force of the thigh muscle to the lower leg and is thus responsible for extension and flexion in the knee joint.

What happens when the patellar tendon is torn?

This is much rarer than a torn cruciate ligament, a rupture of the hamstring tendon or a fracture of the kneecap. In the event of a patellar tendon rupture, patients usually feel a cracking sensation and immediate pain in the knee – and the joint swells.

As the thigh muscle no longer has a lower anchorage after the tear, it shortens and pulls the kneecap upwards with it. Patients can no longer straighten their knee out and can no longer lift the affected leg off the ground.

How does a torn tendon occur?

It can be triggered by a sports accidents in which the force exerted on the tendon is too great – like  when a skier falls or crashes. However, it occurs more frequently in sports like soccer, basketball, volleyball or tennis, which involve a lot of jumping and landing as well as quick stops and changes of direction.

However, a complete rupture of the patellar tendon is quite rare. A patellar tendon is usually damaged before it ruptures completely – due to microtrauma, long-term inflammation or prolonged cortisone therapy.

A completely healthy tendon rarely ruptures. Germany goalkeeper Marc-André ter Stegen has had to have his patellar tendon treated several times in recent years. It was a previous patellar tendon surgery that ruled him out of the Euros in 2021.

How is it treated?

Surgery is required to restore full functionality of the knee. The operation is performed using minimally invasive arthroscopy. The ends of the torn tendon are stitched back together and, if necessary, reinforced with the body's own tendon material.

If the tendon is torn off the bone, it is re-anchored there with drill holes and sutures. The position of the kneecap can be temporarily fixed with wires, which are removed after a few weeks.

How long does the healing process take?

After the operation, it takes six to 12 months for the tendon to heal – even longer if there are complications. As the stability of the sutured tendon only increases after a period of months, at first pressure to the suture must be avoided. The leg is immobilized in an extension splint and only moved during physiotherapy exercises – initially carried out by the physiotherapist, later by the patient.

As a rule, sporting activity is not possible for at least six months. For a professional footballer like ter Stegen, however, the physiotherapy and sports therapy support during rehabilitation will be more intensive than for the average patient, so that he may be able to perform sports exercises earlier and in a more targeted manner than patients who are not working towards a return to professional sport.

What are the possible long-term effects?

This depends on the age of the patient and the severity of the injury, as well as the quality of aftercare and rehabilitation. There may be permanent restrictions in knee function, in terms of joint stability and the ability to move in flexion and extension.

Some patients often have knee pain even after rehabilitation because the tendon becomes inflamed due to strain or scar tissue has formed, which can lead to a new tear. There is also a risk of cartilage damage and osteoarthritis in the affected knee.

Which other athletes have suffered patellar tendon ruptures?

Brazil's former star striker Ronaldo suffered a ruptured patellar tendon in February 2008 while playing for AC Milan. As the then-37-year-old's contract ended shortly afterwards, he moved back to Brazil and returned to the pitch for Corinthians in 2009, playing 52 games there before hanging up his boots in 2011.

Olympic and world champion skier Anna Fenninger from Austria ruptured her patellar tendon in a training crash in October 2015, when she also suffered a torn cruciate ligament and other knee injuries. She had to abandon her first comeback in December 2016 after a short time due to chronic inflammation of the patellar tendon in her other knee. A year later, she tried again and managed to win an Olympic silver medal in the giant slalom in 2018. She ended her career for good after tearing her cruciate ligament again in January 2019.

This article was originally published in German.