Bipartite Patella: Magnetic Resonance Imaging

Objective: Bipartite patella is accepted as a normal anatomic variant of patella, and is identified incidentally on knee radiographs taken for other reasons. The aim of this study was to characterize the magnetic resonance imaging (MRI) features of bipartite patella without bone marrow edema. Materials and Methods: In total, 1.000 patients were evaluated retrospectively. Imaging was performed on 1.5T MRI unit using extremity coil. A standardized knee protocol was used. The obtained images were thereafter analyzed by two experienced radiologists in consensus. Results: Of the 18 patients, six were female and twelve were male. The mean age of the group was 42.1+/-23.5 years. The bipartite fragments were located in the superolateral aspect of the patella. In 16 knees, only one fragment was recognized. The average transverse diameter of the patellar fragment was 11.6+/-8.1 mm. In the axial plane, the average distance between the fragment and the main patella was 1.67+/-1.1 mm. Continuity of the patellar cartilage on the fragment was observed in all patients. The mean fragment cartilage thickness was 1.9+/-1 mm and the patellar cartilage thickness was 3.8+/-2.3 mm. Cartilage signal was present in ten knees, fluid signal was present in six knees, and fibrous signal was present in four knees in the synchondrosis region. Conclusion: A defining feature of bipartite patella without accompanying edema in the bone marrow is a thinner-thannormal cartilage covering the fragments, and an overall cartilage signal over the area of the synchondrosis.