The severe acute respiratory syndrome (SARS) was a highly infectious pneumonia that emerged in southern China early in 2003. A large number of SARS patients experienced large joint arthralgia, although this was, for the most part, not associated with any abnormality on magnetic resonance imaging. The main musculoskeletal complications of SARS were osteonecrosis and reduced bone mass, and these arose not from the disease per se but as a sequel to treatment of SARS with high-dose steroids. SARS patients were almost universally steroid naive with no other known predisposition to osteonecrosis. Prevalence of osteonecrosis in SARS patients treated with steroids ranged from 5% to 58%. Osteonecrosis most commonly affected the proximal femur and femoral condyles and was most strongly related to cumulative steroid dose and duration of steroid therapy. Osteonecrosis risk was <1% in patients receiving <3 g and 13% in patients receiving >3 g cumulative prednisolone-equivalent dose. Most osteonecrotic lesions tended to improve with a reduction in lesion volume over a follow-up period of 5 years. The relative reduction in osteonecrotic lesion volume was greatest for smaller lesions.
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