Irritable hip

Definition/diagnostic criteria Irritable hip, also known as transient synovitis, is a self-limiting condition characterised by inflammation of the synovium of the hip joint. It is predominantly a diagnosis of exclusion, made after ruling out other more serious conditions such as septic arthritis. The condition is typically marked by acute hip pain, limping and restricted range of movement in the hip joint.

Epidemiology Irritable hip is most commonly observed in children between the ages of 3 and 10 years, with a higher incidence in boys than in girls. It is the most common cause of hip pain and limping in this age group, although it can occasionally be seen in adolescents and, rarely, in adults.

Diagnosis
Clinical features: The condition presents acutely with hip pain, which may be accompanied by limping or refusal to bear weight on the affected side.

• The pain may be referred to the thigh or knee, and there is often a history of a preceding upper respiratory tract infection.
• On examination, there is limited and painful internal rotation and abduction of the hip.
• Fever is not typically a prominent feature and, when present, should prompt consideration of other diagnoses.

Investigations: Laboratory investigations often show a mildly elevated ESR and CRP, but these are not diagnostic.

• Ultrasound may show an effusion in the affected hip joint.
• X-rays are typically normal but are important for ruling out other conditions such as fracture or Perthes’ disease.
• MRI is not routinely used but can demonstrate joint effusion and synovial thickening if performed.

Treatment Management of irritable hip is primarily supportive, focusing on symptom relief and the maintenance of hip function.

• NSAIDs such as ibuprofen can be used to manage pain and reduce inflammation. Paracetamol is an alternative, especially if NSAIDs are contraindicated.
• Bed rest is not necessary, and patients should be encouraged to resume normal activities as tolerated.
• Physiotherapy is not routinely required but may be beneficial in cases with prolonged symptoms or significant loss of range of motion.

Prognosis The prognosis is excellent, with most cases resolving spontaneously within one to two weeks. Long-term sequelae are rare, but transient mild stiffness or limping may persist for a few months. Recurrence is observed in up to 15% of cases. Parents and caregivers should be advised to seek further medical attention if symptoms worsen or new symptoms develop, particularly high fever or marked limitation of hip movement, to rule out other more serious conditions.