Bone bruise distribution patterns after patellar dislocation

Bone bruises observed on magnetic resonance imaging (MRI) after patellar dislocation may reveal the underlying injury mechanism, yet three-dimensional patterns remain poorly defined. s: To investigate the typical bone bruising patterns, anatomical, and biomechanical factors after FPD and RPD. Cross-sectional study; Level of evidence, 3. Knee MRI images of patients who experienced patellar dislocation between August 2018 and March 2022 at our institution were selected. Sagittal, coronal, and transverse section planes imaging sequences were used to determine the bone bruise location in the lateral-medial, anterior-posterior, and superior-inferior directions, respectively. Relative bone bruise patterns of the femur and patellar were classified and analyzed. A total of 88 patients (33 men and 53 women, 54 FPD and 32 RPD) met the inclusion criteria, and 77 MRIs with visible bone bruise were analyzed. FPD and RPD share the same relative bone bruise pattern, the shared bone bruise pattern of FPD and RPD was the medial inferior side of the patellar and lateral anterior inferior side of the femur (MIP + LAIF, 56% and 60%, respectively), followed by the medial inferior side of the patellar and lateral posterior inferior of femur (MIP + LPIF, 11% and 10%, respectively). There was no significant correlation between anatomical factors and patellar dislocation. First-time patellar dislocation and recurrent patellar dislocation share the same relative bone bruise pattern of the inferior medial patella and lateral anterior inferior femur, indicating the similar biomechanical and anatomic mechanism. No significant correlation was found between anatomical factors and patellar dislocation.