Dislocation of the patella is when the kneecap (patella) comes right out of the groove in the thighbone (femoral groove) in which it normally rides.

Page updated July 2023 by Dr Sheila Strover (Clinical Editor)

kneecap well located in trochlear groove


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

patellar dislocation


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


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:

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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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Kneecap dislocation

Dr Sheila Strover (Editor)
BSc (Hons), MB BCh, MBA

See biography...

Relevant material -

Journal interpretation - patellar instability

Journal interpretation - 2023 - Framing Patellar Instability: From Diagnosis to the Treatment of the First Episode

- Authors: Maggioni DM et al. and summarised for readers by Dr Sheila Strover (Clinical Editor)

eBook about the unstable patella

eBook - Factors contributing to an Unstable Patella

Easy to read ebook about kneecap dislocation. Free to download. Authored by Dr Sheila Strover (Clinical Editor)