What Is a Patellar Tendon Rupture, and How Is It Repaired?

Key takeaways

• A ruptured patellar tendon is an emergency. You should seek urgent medical attention, not book a scan.
• Surgery to reattach the tendon is usually required within days of the injury.
• Recovery typically takes many months of structured rehabilitation.
• After repair, standing whole-body imaging can help your surgeon check patella position and leg alignment during recovery.
• The patellar tendon is different from the quadriceps tendon, which sits above the kneecap rather than below it.

What are the symptoms of a patellar tendon rupture?

The most obvious symptom is that you cannot straighten your knee after the injury. You may have felt or heard a pop at the front of the knee. The kneecap often rides higher than normal because there is nothing anchoring it from below.

You may also notice a visible gap or dent just below the kneecap where the tendon has torn away. Walking becomes very difficult or impossible.

What causes a patellar tendon to rupture?

The most common cause is a sudden, forceful contraction of the quadriceps muscle while the knee is bent, for example landing from a jump or stumbling off a step. The tendon gives way under the load.

The rupture usually happens at the point where the tendon attaches to the bottom of the kneecap. In some cases it tears from its attachment on the shinbone instead.

How does the extensor mechanism of the knee work?

The extensor mechanism is the chain of structures that allows you to straighten your knee. The quadriceps muscle connects to the top of the kneecap via the quadriceps tendon. The patellar tendon then connects the bottom of the kneecap to the tibial tuberosity, a bony bump at the top of your shinbone. If either tendon ruptures, the chain is broken and the knee cannot extend.

A quadriceps tendon rupture breaks the chain above the kneecap. A patella ligament rupture breaks it below. Both prevent you from straightening your leg, but the surgical approach differs.

How is a torn patellar tendon repaired surgically?

Surgical repair is almost always necessary. The torn ends of the tendon cannot heal on their own because the quadriceps muscle pulls them apart. Surgery is usually carried out within the first week or two of injury for the best results.

What happens during the operation

The surgeon makes an incision over the front of the knee and reattaches the tendon to the kneecap using strong sutures threaded through drill holes in the bone. In some cases, a wire or cable is placed temporarily to protect the repair while it heals. If the tendon tissue is too damaged, a graft from another tendon may be used to reinforce the repair.

The goal is to restore the correct position of the patella so the extensor mechanism works properly again. If the kneecap sits too high after repair, the knee may not bend or straighten normally.

What does patellar tendon repair recovery look like?

Recovery is long and structured. Most people spend several months in a rehabilitation programme that gradually builds quadriceps strength and restores knee range of movement.

Throughout this process, your surgical team will want to check that the patella is sitting in the right position and that leg alignment is on track.

How does standing imaging help after patellar tendon repair?

Standard X-rays are usually taken lying down. That position relaxes the muscles and removes the effect of gravity, so the kneecap may appear to sit normally even when it does not under real-world loading. A standing, weight-bearing image shows where the patella actually sits when you are on your feet.

ScanAlign standing EOS imaging captures a full-length image from your hips to your ankles in one single exposure, with about 90% less radiation than a standard X-ray, around ten times less. This lets your surgeon see the patella position in relation to the whole leg, including any changes in knee alignment or leg length that may have developed during recovery.

Your body is a connected chain. When one knee is immobilised for weeks, the hip, ankle and opposite leg often compensate. A whole-body standing image reveals these compensations so they can be addressed during rehabilitation.

Is a standing alignment scan right for you?

ScanAlign does not assess or treat acute ruptures. Our imaging is designed for the recovery phase, when you and your surgeon want to understand alignment and patella position under real weight-bearing conditions.

Frequently asked questions