ABSTRACT
Objective To explore the MRI appearances of type Ⅴ bone contusion of knee, and explore the diagnostic value and clinical significance of MRI. Methods A retrospective review of 1672 consecutive MRI examinations of acutely injured knees was performed to screen patients with type Ⅴ bone contusion. The MRI findings of them were analyzed by two musculoskeletal radiologists. Results The type Ⅴ bone contusion of knee was found in 43 (2.6%)patients, involving both the inferomedial patella and the anterolateral femoral condyle. Bone contusion was defined as low signal on T_1WI, intermediate or slight hypointense signal on T_2WI,and high signal intensity on fat saturation PDWI, which could be easily detected on axial, sagittal or coronal MR images. Other concomitant specific MR findings included fracture in 9 patients, chondral injury in 29 patients, and lateral patellar subluxation or complete dislocation in 27 patients. Injury of the medial retinaculum was diagnosed and classified in 37 cases, which could be observed best on axial images. Conclusions MRI was accurate in detecting the type Ⅴ bone contusion and that is very helpful for diagnosis and treatment of transient lateral patellar dislocation,and should be used as a routine examination for knee trauma. Axial MR examination should be performed to evaluated the medial patellar retinaculum injury when type Ⅴ bone contusion was found.