Patella (congenital dislocation)

This is an extremely rare condition in which the patella is permanently displaced.

• is thought to be due to failure of internal rotation of the myotome that forms the femur, the quadriceps muscle, and the extensor mechanism. This failure is usually seen towards the eighth to tenth week of embryonic development

The diagnosis of the condition is usually immediately after birth with genu valgum, flexion contracture, and external rotation of the tibia.

• the diagnosis may be delayed until early adulthood or in some instances until late childhood, adolescence, or even adulthood (patients with minimally impaired functions)
• early diagnosis is important in order to start treatment early and to allow improved development of the knee joint (1).

Extensive reconstructive surgery - for example, semitendinosus tenodesis - may be tried but success cannot be guaranteed.

Reference:

• (1) Koplewitz BZ et al. Congenital dislocation of the patella. AJR 2005;184(5):1640-1646