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Transient Synovitis or Septic Arthritis? Evaluating the Kocher Criteria

When a child presents with atraumatic hip pain, the differential includes septic arthritis, transient synovitis, osteomyelitis, slipped capital femoral epiphysis, Legg- Calve-Perthes disease, juvenile idiopathic arthritis, acute rheumatic fever, post strep reactive arthritis, gonococcal arthritis, Henoch-Schoenlein purpura, sickle cell crisis, lyme arthritis, etc. The list is extensive. Fortunately, many of these complaints can be ruled out using a good history, physical exam, and basic laboratory/imaging tests. Two diagnoses, however, are notoriously hard to differentiate without an invasive procedure: septic arthritis and transient synovitis.

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 Acute limping in children

When children with a limp present to you, always consider the possibility of septic arthritis.

Articles of Interest

Approach to the Pediatric Limp

Minor trauma is the most common etiology for a limp, with the median age being 4 years, boys outnumbering girls 2:1, and localization typically to the hip. In those that deny history of trauma, the most common diagnosis is transient synovitis, with 77% having a benign cause without requiring surgical intervention or hospital admission.

Pediatric Nontraumatic Hip Pathology

Transient synovitis is the most common diagnosis among patients with nontraumatic pediatric hip complaints.

Transient Synovitis vs Septic Arthritis of the Hip

TS is an inflammation of the joint space, classically following a URI, with a benign clinical course. SA is an infectious arthritis associated with poor outcomes with diagnostic delays, including osteonecrosis, growth arrest, and sepsis. Both can both present as an atraumatic, acutely irritable hip with progressive signs of fever, limp, refusal to bear weight, limited range of motion, and abnormal labs. This overlap makes them difficult to differentiate.

Resources

Kocher Criteria

Distinguishes septic arthritis from transient synovitis in a child with an inflamed hip.

StatPearls

TS most commonly presents as acute unilateral limb disuse ranging from nonspecific hip pain or subtle limp to a refusal to bear weight. Depending on the age of the patient, the history may only be significant for the child or infant becoming increasingly agitated or crying more often than at baseline. Therefore, heightened clinical suspicion is warranted in younger pediatric patients and infants.