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Patellar tendon tear

Tendons are strong cords of fibrous tissue that attach muscles to bones. The patellar tendon works with the muscles in the front of your thigh to straighten your leg.

Small tears of the tendon can make it difficult to walk and participate in other daily activities. A large tear of the patellar tendon is a disabling injury. It usually requires surgery and physical therapy to regain full knee function.

Causes and risk factors

A very strong force is required to tear the patellar tendon.

Falls – Direct impact to the front of the knee from a fall or other blow is a common cause of tears.

Cuts – often associated with this type of injury.

Jumping – The patellar tendon usually tears when the knee is bent and the foot planted, like when landing from a jump or jumping up.

A weakened patellar tendon is more likely to tear. Several things can lead to tendon weakness such as patellar tendinitis, chronic disease, and steroid use.


When a patellar tendon tears there is often a tearing or popping sensation. Pain and swelling typically follow, and you may not be able to straighten your knee. Additional symptoms include:

  • An indentation at the bottom of your kneecap where the patellar tendon tore
  • Bruising
  • Tenderness
  • Cramping
  • Your kneecap may move up into the thigh because it is no longer anchored to your shinbone
  • Difficulty walking due to the knee buckling or giving way

Diagnosis and treatment

Your doctor will consider several things when planning your treatment, including:

  • The type and size of your tear
  • Your activity level
  • Your age

Very small, partial tears respond well to nonsurgical treatment including immobilization and physical therapy. Most people require surgery to regain knee function. Surgical repair reattaches the torn tendon to the kneecap. People who require surgery do better if the repair is performed soon after the injury. Early repair may prevent the tendon from scarring and tightening into a shortened position.