Bipartite patella

In around 1% - 2% of the population the patella develops as two unfused ossification centers which lead to the condition known as bipartite patella.

• affects men more than women (1)
• common in adolescence (2)
• the two parts of the bone are connected by thick fibrous tissue (1)

This anomaly affects the outer quadrants of the patella, and gives the appearance on radiograph of a patella made up of two parts.

The condition is normally asymptomatic, incidental finding and should not be mistaken for a fracture.

• standing or jumping may cause pain (1)
• may occasionally cause anterior knee pain (3)
• soft tissue tenderness might be present over the location of the bipartite patella, (commonly the superolateral pole of the patella) (2,3)

Stress fracture superimposed on bipartite patella may cause difficulty in recognizing the clinical entity (1).

Initially the patients can be managed with conservative therapy - modified activity and local flexibility and strengthening exercises (3). Patients with severe pain should be referred to an orthopaedic surgeon (2). Fragment excision relieves pain.

Reference:

• (1) Christian SR et al. Imaging of anterior knee pain.  Clin Sports Med. 2006;25(4):681-702
• (2) Gilchrist I. Anterior knee pain. Arthritis Research UK 2004
• (3) Houghton KM. Review for the generalist: evaluation of anterior knee pain. Pediatr Rheumatol Online J. 2007;5:8.