Horizontal bipartate patella

Case
A twelve-year-old male football player presented with an acute onset of anterior knee pain. He described experiencing pain when he jumped to head a ball. This did not immediately seem too bad and he was able to continue. After about 5-10 minutes however he asked to be substituted as his knee had become more painful. Two weeks later his knee remained painful, but was improving. His main positive finding was of localised tenderness about the patella and patella tendon. His extensor mechanism was intact (he could straight leg raise without any problems), there was no effusion and there was an otherwise normal knee examination.

Findings
X-ray images show a bipartite patella with a transverse synchondrosis at the junction of the proximal two thirds and distal third. The MRI shows only mildly increased signal intensity adjacent to the deep aspect of the synchondrosis. The synchondrosis itself appears intact with no separating fluid cleft, fracture or other abnormality. The patellofemoral articular cartilage appears preserved. An x-ray of the contralateral (asymptomatic) knee was normal with no evidence of a bipartate patella.

Discussion
This young player was initially managed with a two-week period in a knee brace. At this stage his tenderness had improved and he could walk without pain. He avoided running based training for a further four weeks. He was able to return to football without restriction by 10 weeks post-injury.

A bipartite patella (two-part patella) is a patella with an unfused accessory ossification centre. The majority of these involve the superolateral aspect (approximately 75% of cases) or the lateral margin (20-25% of cases). The inferior pole is involved less than 1% of the time. A bipartate patella is frequently an incidental finding and generally has no clinical relevance. When symptomatic, there is generally localised tenderness directly over the synchondrosis. In the majority of cases, a symptomatic bipartite patella improves without surgery. In our clinic, excision of the small fragment is rarely done and often is unrewarding.

Important notice
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