Secondary osteonecrosis of the knee as a part of long COVID-19 syndrome: a case series.

COVID-19 infection affects different organ systems with long-term sequelae, which has been termed as long COVID-19 syndrome. To the best of our knowledge, osteonecrosis of the knee as a part of long COVID-19 syndrome has not been documented. Corticosteroids are being used extensively in moderate and severe cases of COVID-19. We report two cases who developed osteonecrosis of the knee after being treated for COVID-19 infection. In our case series, the mean cumulative dose of prednisolone was 1156.5 mg (900-1413 mg), which is less than the cumulative dose reported in literature for osteonecrosis of the knee. In our case series, the patients developed symptomatic osteonecrosis at a mean interval of 73 days after initiation of steroid therapy, with the earliest presenting at 25 days. Early diagnosis of osteonecrosis of the knee on high clinical suspicion by MRI would help in early intervention with bisphosphonate therapy.