Transient Synovitis vs. Septic Arthritis
Today’s post will focus primarily on transient synovitis vs. septic arthritis in children (you can see other differentials below, but we won’t explore their work-up today) . Transient synovitis is relatively common (with a prospective lifetime occurrence of 3%), however it is important to do your due diligence on a pediatric patient presenting with hip pain, and it is imperative to distinguish it from septic arthritis.
Presentation: 4 year old male comes in refusing to bear weight on his left leg. No history of trauma. According to the family the patient did have a “head cold,” approximately 1 week ago. Vitals are stable and patient is afebrile.
Differential includes acute rheumatic fever, developmental dysplasia of hip, fracture, Legg-Calve-Perthes disease, septic arthritis, slipped capital femoral epiphysis, transient synovitis, and osteosarcoma.
The key to this work-up is your clinical suspicion and evidence gathering:
Xray: to rule out structural changes (i.e. fracture, SCFE, ect.)
Ultrasound to look for effusion.
The presence of effusion does not rule in or out transient synovitis.
Gold standard dx: US guided arthrocentesis
Kocher criteria (see mdCalc) can help guide decision making but it is really only helpful if you have a patient on either extreme of the criteria.
Below is a table of features/lab values to help decision making.
Without an arthrocentesis, distinguishing septic joint for transient tenosynovitis can be difficult, and septic joint is a “do not miss.” Gather your evidence and consult your specialists.
Nigrovic, P.A. (2021). Approach to hip pain in childhood. In T.W. Post, J. Drutz, W. Phillips, S. Li, M. Torchia (Eds.), UpToDate. Available from https://www.uptodate.com/contents/approach-to-hip-pain-in-childhood?search=transient%20synovitis&source=search_result&selectedTitle=1~14&usage_type=default&display_rank=1#H18