In patellofemoral instabilty the patella (kneecap) changes its relationship to the groove of the femur bone (thighbone) and may partially or fully de-rail.

patellar subluxation

Subluxation.

patellar dislocation

Dislocation.

 

Causes of patellofemoral instability

The patella may be unstable for a number of reasons. There may be local reasons related to the patella, such as patella alta, or related to the trochlear groove, such as trochlear dysplasia. There may also be remote causes in the hip or the foot - such as rotational deformities.

Synonyms: 
patellar instability
kneecap instability
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The unstable patella

A discussion about patellar instability, the factors that may cause the patella to sublux or dislocate, and what can be done about it.

Patellar instability and dislocation

Discussing how the anatomy can affect the tendency to dislocate the patella.

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