Dislocation of the patella

Normal situation where the patella is well located in the underlying groove of the femur.

Patellar dislocation, where the patella has jumped completely out of the groove.

• How common is patellar dislocation?
• What allows the kneecap to dislocate?
• Consequences of MPFL tear after dislocation

How common is patellar dislocation?

Dislocation of the patella is most common in young people (16-20 years) and most frequent in the female sex.

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What allows the kneecap to dislocate?

Dislocation may follow a traumatic event, like a blow on the knee. Frequently, however, there is an underlying anatomical problem that predisposes the knee to patellar instability. Such anatomical problems include:

• trochlear dysplasia
• patellar dysplasia
• patella alta

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Consequences of MPFL tear after dislocation

It is common to tear the medial patellofemoral ligament (MPFL) during a dislocation event, which then makes it easier for the patella to dislocate again. Most early surgery would be focused on addressing this problem and reconstructing the ligament.

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