COVID-19 patients admitted to the Intensive Care Unit may develop painful range of motion restrictions of the large joints due to heterotopic ossifications. Here we describe two patients who developed restricted and painful passive and active mobility of the hips, shoulders and elbows after mechanical ventilation because of respiratory failure due to COVID-19 pneumonia. Conventional radiography showed extensive heterotopic ossifications. Retrospectively, alkaline phosphatase levels were elevated. It is likely that local and systemic factors contribute to the development of heterotopic ossifications. Early diagnosis is important to provide complementary non-pharmacological interventions (gentle passive mobilization) and medication (non-steroidal anti-inflammatory drugs, such as indomethacin). If pain and limited joint mobility remain present, surgical removal of ectopic bone could be considered. Future trials are needed to systematically map the prevalence of heterotopic ossifications in COVID-19 patients who were admitted to the Intensive Care Unit, andto evaluate whether prophylactic treatment with non-steroidal anti-inflammatory drug is of relevance.