[Occult bone trauma detected by magnetic resonance imaging]

Authors deal with a case of a 23-year old women presented with a sport-related injury of the left knee joint. Initially seen in the surgical department, patient presented with pain, swelling, and decreased range of motion of the left knee. Conventional radiographs of the left knee showed no evidence of fracture or osseous abnormality, while the puncture of the joint proved haemarthros. One day later surgical examination demonstrated repeatedly pain and swelling of the left knee expanding to the proximal third of the leg. Repeated puncture exhibited haemorrhagic synovial fluid containing fat tissue, lipohaermarthos. With regard to the contradiction between the surgical examination and negative radiographs, the MRI examination was recommended. MR images revealed linear area of abnormal signal intensity in the medial condyle of the tibia indicating subchondral fracture of the posterior margin of the medial tibial condyle. This finding was associated with increased volume of the haemorrhagic intraarticular fluid. The menisci, intraarticular and capsular ligamentous apparatus was noted to be intact. The control MR examination performed six weeks later demonstrated healed fracture with surrounding bone marrow edema. The importance of non-invasive MR examination for revealing of the occult bone fractures is stressed.