Corticosteroid-induced Knee Osteonecrosis and Accompanying Femoral Head Osteonecrosis

Introduction: The aim of this study was to investigate the prevalence and magnetic resonance imaging (MRI) findings of knee osteonecrosis (ON) in patients with arthralgia who received corticosteroid therapy. We also aimed to demonstrate the diagnostic performance of plain radiography in knee ON when MRI is accepted as the gold standard and to investigate the prevalence of accompanying femoral head ON in patients who underwent hip MRI. Methods: One hundred and sixty-two knee X-rays and MRI examinations of 136 patients with knee pain and a history of corticosteroid intake were retrospectively evaluated for the presence of ON. Localization, maximum size of dominant lesion, multiplicity of lesions, presence of bone edema, double-line sign and subchondral extension were evaluated in patients with ON. Accompanying femoral head ON was also investigated in patients who underwent hip MRI. Results: MRI revealed ON in 37 knees of 28 patients. The sensitivity and specificity of plain radiography in the diagnosis of knee joint ON was 29.73% and 98.40%, respectively. There were multiple lesions in 31 knees and subchondral space was affected in 24 knees. The double-line sign and bone marrow edema were present in most of the lesions. Of the 28 patients with knee ON, only 16 had hip joint MRI and five of these patients (31.3%) had femoral head ON. Conclusion: Plain radiography has low sensitivity but high specificity for the diagnosis of knee ON. Corticosteroid-induced ON tends to be multifocal, and a significant proportion of patients with knee ON during corticosteroid therapy have ON of the hip joint.