21 On T1-weighted images, the alterations in the subchondral bone marrow signal are characterized by ill-defined low signal intensity, compared with the unaffected bone marrow. The ability to identify a bone bruise is unique to MR studies. 20 In time, bone marrow edema earned the moniker bone bruise to reflect its traumatic nature. This discrepancy in the imaging studies was labeled bone marrow edema owing to the “lack of a better term and to emphasize the generic character of the condition.” 30 The proposed pathogenesis of these marrow changes asserts that increased blood pooling, edema, reactive hyperemia, and possible microfracture of the trabecular subchondral bone alter the marrow signal intensity. 30 On T2-weighted magnetic resonance (MR) images, they recognized an ill-defined hyperintensity in the bone marrow where standard radiographs showed nonspecific osteopenia or normal findings. Evaluate for other associated injuries especially in high-energy fracture patterns (Type IV, V, VI).In 1988, Wilson et al introduced the term bone marrow edema in describing a group of patients with atraumatic debilitating knee and hip pain.Complex bicondylar fracture with separation of condylar components from diaphysis.Results from combination of high-energy forces.Type VI: plateau fracture with separation of metaphysis from diaphysis.Results from pure axial force on extended knee, high-energy injury.Medial and lateral plateau fractures with or without compression.Medial plateau stronger than lateral, represents higher energy injury than Types I, II, III.Results from axial or varus stress, split or split-depression fracture.Rare and see only in older individuals or those with severe osteopenia.Compression fracture of lateral plateau, usually laterally or centrally located.Type III: lateral plateau, isolated depression fracture (rare).Same mechanism of injury as Type I but with underlying osteopenic bone unable to resist depression.Type II: lateral plateau, split-depression fracture (most common).Cancellous bone of lateral plateau prevents depression in young healthy patients.Results from axial load with valgus stress.Type I: lateral plateau, split fracture.Frequently required for further characterization of fracture pattern and evaluation of involvement of articular surface, as well as preoperative planning.May be necessary for fracture diagnosis in the ED, especially if clinical suspicion persists despite negative x-rays.The latter is seen best on cross-table lateral view when the beam is tangential to the fat-blood interface. Knee effusions and lipohemarthrosis (fat-fluid level), although non-specific, may indicate underlying bony injury.Joint widening is not reliable sign in standard AP because it requires a weight bearing view which should not be attempted if this injury is suspected.Increased trabecular density may represent compression fracture (see image B).Fractures can be subtle as slope of tibial plateau makes accurate assessment of depression difficult on AP view.Medial Tibial Plateau Fracture (Case courtesy of RMH Core Conditions,.
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