Transient synovitis (TS) is a self-limiting disease characterized clinically by acute hip pain. The diagnosis is confirmed by excluding other severe diseases, such as septic arthritis, osteomyelitis, and Legg-Calvé-Perthes disease. Ultrasonography examination frequently reveals hip effusion. 1,2 A point-of-care ultrasonography (POCUS) decision-support algorithm (DSA) is regularly used to identify TS in the pediatric emergency department (ED) of Rambam Health Care Campus, a tertiary hospital in Haifa, Israel. 2,3 The POCUS-DSA includes a set of 5 clinical criteria that must be met, followed by bedside ultrasonography examination of the hip joint (Figure ). 1,2 Here, we evaluate the performance of the POCUS-DSA in the diagnosis of TS among children presenting to the pediatric ED. MethodsThis study was approved by the Rambam Health Care Campus ethics committee. Informed consent was not necessary because of the retrospective nature of the study, in accordance with Rambam Health Care Campus policy. The reporting guideline for case series was used for this study. This case series analyzed all children with nontraumatic hip tenderness who met the POCUS-DSA criteria between January 1, 2014, and December 31, 2019. Ultrasonography was performed using an accepted technique. 2 Patients with hip effusion received a diagnosis of TS in the ED and were scheduled for a follow-up visit in 5 to 7 days. Patients without hip effusion were assessed with laboratory or imaging tests, as per clinician judgment (Figure). 2 A final diagnosis of TS was made for any patient who had spontaneous resolution of symptoms and a reduction in the amount of effusion at the follow-up visit. 1 Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR), and negative LR were used to assess Author affiliations and article information are listed at the end of this article.