Transient Bone Marrow Edema Syndrome of the Knee: Clinical and Magnetic Resonance Imaging Results at 5 Years After Core Decompression

Purpose: We report on 24 cases of transient bone marrow edema syndrome in 18 patients who underwent core decompression of the knee. Methods: Diagnosis was made with the use of radiographs, magnetic resonance imaging (MRI), and core biopsy testing. Arthroscopic surgery and core decompression were carried out in all patients, and MRI was performed again, 5 years after surgery was performed. Results: Medial and lateral femoral condyles were affected in 15 and 7 knees, respectively. In all, 6 patients presented with bilateral involvement of the knees (migrating transient bone marrow edema syndrome). Two of these patients had affections of the medial and lateral compartments within the same knee at different times, consistent with intra-articular regional bone marrow edema syndrome. Core biopsy specimens showed areas of bone marrow edema and vital trabeculae covered by osteoblasts and osteoid seams. Resolution of symptoms and normalization of MRI findings occurred in all patients within 12 weeks after surgery. Conclusions: Migrating bone marrow edema was found in a high percentage (33%) of patients at 5-year follow-up; however, all patients were clinically asymptomatic, and signal alterations on MRI had resolved completely. The high incidence of migrating bone marrow edema, the lack of osteonecrotic regions in our specimens, and the fact that none of these cases progressed to spontaneous osteonecrosis seem to further support the contention that bone marrow edema syndrome of the knee is a distinct entity. Level of Evidence: Level II, diagnostic study; development of diagnostic criteria on the basis of consecutive patients and with universally applied reference gold standard.