The painful bipartite patella.

Two skeletally immature patients with bipartite patella, a lesion normally classified as a developmental variation, proved to have a symptomatic lesion with a traumatic etiology. In both patients, appropriate treatment resulted in complete subsidence of symptoms; one patient was treated with cast immobilization, while the other eventually required surgical resection. In addition, normal and bipartite patellar specimens from skeletally immature cadavers were histologically and morphologically assessed. These clinical and anatomic studies suggest that in some cases a bipartite patella may be a traumatically induced, chondroosseous disruption of the superolateral pole of the incompletely ossified patella, analogous to Sinding-Larsen-Johansson disease at the inferior patellar pole or Osgood-Schlatter disease in the tibial tuberosity. The possibility of bipartite patella being such a chronic stress fracture in a symptomatic patient should be considered in order to render appropriate treatment.