Ressonância magnética da osteonecrose do joelho: estudo de 19 casos* Magnetic resonance imaging of knee osteonecrosis: a study of 19 cases

OBJETIVO: Descrever os achados epidemiologicos, clinicos e de ressonância magnetica da osteonecrosedas porcoes distal do femur e proximal da tibia. MATERIAIS E METODOS: Avaliacao de 19 pacientes (12mulheres e 7 homens), sem historia previa de fatores causais, com achados a ressonância magnetica suges-tivos de osteonecrose do plato tibial ou condilo femoral. RESULTADOS: Verificou-se a presenca de anorma-lidades osteocondrais em 63,1% dos casos e em 73,6% destes houve associacao com lesao meniscal ipsi-lateral. Houve tambem importante associacao com edema na medular ossea em correspondencia (grau IIIem 16 casos). CONCLUSAO: A ressonância magnetica demonstrou ser um metodo nao invasivo com boasensibilidade no diagnostico da osteonecrose do joelho, bem como das lesoes associadas, sendo mais fre-quente nas mulheres (63% dos casos).Unitermos: Osteonecrose; Imagem por ressonância magnetica; Anormalidades subcondrais.OBJECTIVE: To describe epidemiological, clinical and magnetic resonance imaging findings of osteonecrosisin the distal femur and proximal tibia. MATERIALS AND METHODS: Evaluation of 19 patients (12 womenand 7 men), with no previous history of causative factors, with magnetic resonance imaging findings suggestiveof osteonecrosis in the tibial plateau or femoral condyle. RESULTS: Osteochondral abnormalities were observedin 63.1% of the cases; in 73.6% of them, such abnormality was associated with ipsilateral meniscal lesion.Also, a significant association with bone marrow edema (grade III in 16 cases) was observed. CONCLUSION:Magnetic resonance imaging has demonstrated to be a noninvasive method with good sensitivity in thediagnosis of knee osteonecrosis as well as of associated lesions which are most frequently found in women(63% of cases).Keywords: Osteonecrosis; Magnetic resonance imaging; Subchondral abnormalities.