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kneecap (patella) dislocation

What is kneecap (patella) dislocation?

A dislocated kneecap occurs when the patella (kneecap) that sits over the front of the knee comes out of its groove at the end of the thigh bone (femur), coming to rest on the outside of the knee joint. This can cause stretching or tearing to the supporting ligaments and tendons.

Normally, the kneecap glides smoothly over a groove in the joint when you bend or straighten your leg but if the kneecap is dislocated you may be unable to bend or straighten your leg. A dislocated kneecap is a common injury that can take around 6 weeks to heal. If you have dislocated your kneecap once it is far more likely to dislocate in the future.

Kneecap dislocation is not the same as knee dislocation.

George’s MPFL reconstruction story

“Our hopes are that George will make a full recovery and carry on playing rugby to an elite level. So far the signs are incredible.”

What causes a dislocated kneecap?

A dislocated kneecap can be caused by:

  • A blow to the knee, for example if the knee joint collides with another person or object with great force.
  • A sudden change of direction while the leg is still planted firmly on the ground, such as during sports or dancing.
  • Weak leg muscles which puts pressure on the knee joint.
  • A misaligned or elevated kneecap.

Being tall and/or being overweight increases the risk of dislocation and women are also more at risk.

After a dislocated kneecap, the medial patellofemoral ligament may become torn. This is the ligament that secures the kneecap to the inside (medial) of the knee. Once it is torn it may not heal with the same level of tension as before. This can lead to recurrent dislocation of the kneecap.

Dislocated kneecap

Knee consultants

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