Transient Synovitis as a Sequela of COVID-19 Infection: A Case Report and Review of Literature.

Introduction: Transient synovitis (TS) in the setting of a COVID-19 infection has been reported only a few times in the literature. We report a case of TS 5 weeks following a positive COVID-19 test, in which three modified Kocher criteria were met. We aim to summarize and compare the clinical presentations of prior reported cases, and to expand the current understanding of extrapulmonary manifestations of COVID-19. Case Report: A 4-year-old female presented with right hip pain and refusal to bear weight on the extremity without a history of trauma. Five weeks prior, the patient tested positive for SARS-Cov-2. The patient met three modified Kocher criteria and an ultrasound of the right hip demonstrated a 6 mm effusion. Synovial fluid analysis and cultures were negative for septic arthritis. The patient was admitted for observation and started on non-steroidal anti-inflammatory drugs with improvement in her pain. Conclusion: We report a case of TS 5 weeks following COVID-19 infection, and provide a review of the six prior reported cases. Our case differs from prior cases in the timing of hip pain after initial upper respiratory infection symptoms, and the number of modified Kocher criteria met. In the setting of pediatric hip pain, it is important to consider COVID-19 infection as a cause of TS.