Bipartite Patella

Patellar fractures can occur from direct and indirect mechanisms, with a direct force being the commonest cause. Potential mechanisms include a powerful quadriceps contraction, a direct anterior blow which may result in an open fracture and patellar dislocation or relocation. It is important to differentiate a fracture from a bipartite patella which has a characteristic location and smooth margins. 

Bipartite patella is a common anatomic variant caused by the nonunion of an accessory ossification center of the bone. Three types of anomaly have been described (Fig. 14.25) the type 1 anomaly is characterized by a separate nucleus at the lower pole of the patella type 2 describes a more elongated fragment on the lateral side of the bone type 3 is typified by a separate nucleus at its superolateral aspect. Types 1 and 2 are rarely encountered in clinical practice,... 

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