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Acute limping in children

So how can one differentiate between transient synovitis and septic arthritis?

Clinical exam – this is the most important differentiator. Children with septic arthritis look sick. They are unwell, tired, possibly lethargic and will do very little activity. With transient synovitis, parents may report limping as the only ‘new’ finding, as the child will likely be active, alert, feed and in general – will look well.

Physical examination – Examination in young, non-cooperative children, is always challenging. When the child is cooperative, he or she may have limited range of motion (mostly internal rotation of the hip), and with septic arthritis…

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  Kocher Criteria for Septic Arthritis

The prediction rule was developed for the hip in children. It has been used for other joints such as the knee, however it was not developed for the knee and may not be valid. Also it was not developed in infants or adults, so it may not apply to these populations.

  Septic Arthritis

Despite the name, toxic synovitis is the self-limited, benign inflammation of the joint that gets treated symptomatically. Unfortunately, the presentation of toxic synovitis can be difficult to differentiate from septic arthritis, particularly when involving the hip joint.

 Transient Synovitis or Septic Arthritis? Evaluating the Kocher Criteria

Both present with an atraumatic, acutely irritable hip sometimes with associated limp, fever, refusal to bear weight, limited ROM, and/or joint effusion on x-ray and ultrasound. It is imperative to differentiate the two as the treatment and course of the two diseases are very different.

 Transient Synovitis vs Septic Arthritis of the Hip

Given that the Kocher clinical criteria and imaging (XR and US) modalities are only moderately helpful, at best, you should use a combination of your history and physical findings, imaging results, and gestalt to help guide your management decisions. Many clinicians err conservatively and perform an arthrocentesis in uncertain cases despite it being a relatively invasive procedure.

Articles of Interest

Emergency Department Management of Pediatric Septic Arthritis and Osteomyelitis

Septic arthritis and osteomyelitis in pediatric patients represent true emergencies, and can quickly threaten life and limb. A high index of suspicion should be maintained, as these conditions often present with a subacute course of illness and vague signs and symptoms. Septic arthritis and osteomyelitis can occur concurrently, so suspicion for one should also prompt investigation for the other.

Pediatric Septic Hip

Caveat: Though Kocher criteria is the most studied decision tool, it is far from perfect. A Kocher score of 0 does not rule out the disease (Caird 2006) but a positive screen should heighten suspicion

Septic Arthritis Basics

Septic Arthritis needs to be higher on your differential than Toxic Synovitis.

Septic arthritis in children

Unfortunately, diagnosing septic arthritis is not always straightforward. Transient synovitis is a benign, self-limiting condition that mimics septic arthritis. Other less common orthopaedic conditions can also present in a similar fashion, and need to be excluded.