Bipartite Patella

patella bipartita

A bipartite patella results from failure of fusion of an accessory ossification centre with the main patella, producing a persistent fibrocartilaginous junction between a superolateral fragment and the main patellar body. It is present in 1-6% of the population, bilateral in 50% of cases. The fragment is connected to the main patella by fibrocartilage at the superolateral corner, where the vastus lateralis and lateral retinaculum attach.

Anatomical Data

Structure & Landmarks

Articulations	Fibrocartilaginous junction between main patella and superolateral fragment Trochlear groove (main patella articulates normally)
Landmarks	Superolateral patellar corner (95% of bipartite cases) Fibrocartilaginous junction palpable as a gap in the superolateral patella Bilateral in 50%; male predominance (3:1) AP radiograph: rounded superolateral fragment with smooth sclerotic edges
Ossification	Results from failure of a secondary ossification centre, usually at the superolateral pole, to fuse with the main patellar centre that appears at about 3-6 years.

Clinical Relevance

Clinical Notes

The bipartite patella must be distinguished from patellar fracture on radiograph: the superolateral location, smooth rounded fragment edges, and sclerotic margins distinguish bipartite anatomy from acute fracture (irregular edges, no sclerosis). Symptomatic bipartite patella produces anterolateral knee pain reproduced by resisted quadriceps contraction and localised tenderness at the fibrocartilaginous junction, seen in adolescent athletes with repetitive jumping. Treatment includes activity modification, vastus lateralis release reducing tension on the fragment, or excision of the fragment in refractory cases.

Pathology

Common Injuries & Conditions

Symptomatic Bipartite Patella in Adolescent Athletes

Repetitive quadriceps loading in jumping sports stresses the fibrocartilaginous junction between the bipartite fragment and the main patella, producing superolateral knee pain and local tenderness at the junction; MRI shows marrow oedema in the fragment and junction disruption; vastus lateralis release reduces the pull on the fragment and resolves symptoms in most athletes.

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