Transient synovitis of the hip or Irritable hip
Transient synovitis of the hip is a self-limiting, post-infectious inflammatory arthritis. Synonyms are toxic synovitis and irritable hip.
It is the most common cause of limping in children.
It is due to swelling of the lining of the hip joint.
Transient synovitis of the hip is an idiopathic disorder.
And it is often preceded by a viral infection such as nonspecific upper respiratory tract infection or diarrhea. However transient synovitis of the hip can occur after a fall or injury in some cases.
Transient synovitis of the hip is seen most often in children between 3 and 8 years of age.
It manifests with the sudden onset of pain in the hip, groin, thigh, or knee and may have a limp or difficulty crawling or standing.
Boys are more commonly affected.
On examination, the child will be afebrile and will have a nontoxic clinical appearance.
Young children may be comfortable sitting in the mother’s lap but become very guarded with any attempt at the examination.
The child may refuse to walk while walking limp will be present.
There is a loss of internal rotation of the hip and it is usually held in flexion, abducted, and externally rotated.
Transient synovitis of the hip is a clinical diagnosis and no tests are required to make the diagnosis. However, investigations are required to rule out other conditions.
Plain radiographs often show no abnormality or may show a small widening of the joint space.
Ultrasound is a sensitive and reliable method to confirm the presence of an effusion.
White blood cell (WBC) count, C – reactive protein level (CRP) and erythrocyte sedimentation rate (ESR) is usually normal or marginally elevated.
Septic arthritis is ruled out by joint aspiration and synovial fluid analysis. Joint aspirate usually reveals a WBC count between 5000 and 15,000 cells/mL, with more than 25% polymorphonuclear leukocytes.
Magnetic Resonance Imaging (MRI) may be considered to evaluate for periarticular pyomyositis or osteomyelitis is suspected, if there is significant lab abnormality.
Rest with close observation and non-steroidal anti-inflammatory drugs are appropriate.
Most children will have a complete resolution within 2 weeks.
There are no significant long term sequelae. Recurrence of 4 – 26 % is noted within the first 6 months after the initial onset. 0 -10% incidence of subsequent Perthes disease has been reported.