Bone marrow edema pattern in osteoarthritic knees: Correlation between MR imaging and histologic findings

PURPOSE: To correlate magnetic resonance (MR) images of a bone marrow edema pattern with histologic findings in osteoarthritic knees. MATERIALS AND METHODS: Sixteen consecutive patients (age range, 43-79 years; mean, 67 years) referred for total knee replacement were examined With sagittal short inversion time inversion-recovery (STIR) and T1- and T2-weighted turbo spin-echo MR imaging 1-4 days before surgery. Tibial plateau abnormalities on MR images were compared quantitatively with those on histologic maps. RESULTS: The bone marrow edema pattern zone (ill-defined and hyperintense on STIR images and hypointense on T1-weighted MR images) mainly consisted normal tissue (53% of the area was fatty marrow, 16% was intact trabeculae, and 2% was blood vessels) and a smaller proportion of several abnormalities (bone marrow necrosis [11% of area], abnormal [necrotic or remodeled] trabeculae [8%], bone marrow fibrosis [4%], bone marrow edema [4%], and bone marrow bleeding[2%]). The bone marrow edema pattern zone and the zone with a normal MR imaging appearance differed significantly in the presence of bone marrow necrosis (P = .021), bone marrow fibrosis (P = .014), and abnormal trabeculae (P = .011) but not in the prevalence of bone marrow edema (P = .069). Bone marrow edema also was:: found in zones with an unremarkable MR appearance (perifocal zone, 5% edema; control zone, 2% edema). CONCLUSION: A bone marrow edema pattern in osteoarthritic knees-represents a number of noncharacteristic histologic abnormalities. Edema is-not a major constituent of MR imaging signal intensity abnormalities in such knees.