We evaluated the histopathologic and cryosectional appearance of bone bruise injuries of the knee detected on MRI. Histologic evaluation of bone biopsies from 3 patients revealed microfractures of cancellous bone, edema and bleeding in the fatty marrow. Between intact lamellar bone trabecules, fragments of hyaline cartilage mixed with highly fragmented bone trabecules were found. Postmortem specimens were obtained from 2 more patients, killed in motor vehicle accidents. MRI revealed bone bruise injuries of the lateral femoral condyle and of the lateral tibial plateau in 1 knee and anterior cruciate ligament disruption, a medial meniscus tear and bone bruise injury of the tibial plateau and of the lateral femoral condyle in the other specimen. The specimens were embedded in physiologic saline solution and frozen to -30 degrees C. By rotationcryotomy, 1 mm slices were removed from the surface of the specimens and documented on photographs. Subchondral lesions and bleeding were found, corresponding to the MR images.