ABSTRACT
Background: SARS-CoV-2 is the virus responsible for COVID-19. Patients with Covid-19 manifested symptoms mainly related to the respiratory system, but also the musculoskeletal system can be involved. Covid-19 has been described as a possible cause of knee osteonecrosis (ON). We performed a systematic review to investigate the hypothetical correlation between Covid-19 and knee ON. Methods: Inclusion criteria were all articles reporting cases of knee ON after a diagnosis of SARS-CoV-2 infection. Considering that Covid-19 is an emerging disease, we included all levels of evidence studies. Results: We finally included 2 case series and 2 case reports. We extracted data regarding demographic and clinical characteristics, details of magnetic resonance imaging (MRI), use of corticosteroids (CCS), temporal correlation between ON and Covid-19, treatment of the lesion and its outcomes. A total of 6 cases of post-Covid knee ON have been described. Knee pain arose on average 8 weeks after the diagnosis of Covid-19. All patients had knee MRI showing osteonecrosis. CCS were used to treat COVID-19-related symptoms in 3 cases. The medial femoral condyle was always involved by ON. Conservative treatment was successful in 4 patients. Conclusions: It is unclear the correlation between COVID-19 and ON. Probably post Covid-19 osteonecrosis has a multifactorial origin in which factors related to the patient, consequences of Covid-19 and CCS therapy add up to cause a reduction of blood supply and bone vitality until ON is triggered. A greater number of patients is needed to clarify the role of Covid-19 in the etiopathogenesis of knee ON.