Transient synovitis is sometimes referred to as irritable hip. It generally presents as acute hip pain following a recent viral infection.

Epidemiology:

• It is the commonest cause of hip pain in children.
• The typical age group is 3-8 years.
• Affects boys more than girls

Features

• limp/refusal to weight bear
• groin or hip pain
• a low-grade fever is present in a minority of patients
  • high fever should raise the suspicion of other causes such as septic arthritis

Transient synovitis is self-limiting, requiring only rest and analgesia.

NICE Clinical Knowledge Summaries help us with the difficult task of excluding septic arthritis and other serious diagnoses in children who present with a limp. They suggest:

• fever is a red flag, indicating the need for urgent specialist assessment
• children may be monitored in primary care (with a presumptive diagnosis of transient synovitis) 'If the child is aged 3–9 years, well, afebrile, mobile but limping, and has had the symptoms for less than 72 hours

Kochers criteria states certain factors that make a diagnosis of septic arthritis more likely:

• Fever >38.5
• Refusal to weight bear on affected side