Definition
Transient synovitis of unknown aetiology with complete resolution
Epidemiology
Most common cause of hip pain
- 1 /1000
May occur in 3% of children with majority not seeking medical attention
Wide range of age
- from 9 / 12 to teenagers
- usually 3 - 8 years
- peak 6 years / same as Perthes
More common in
- boys 2:1
- caucasian
- never bilateral
Aetiology
1/3 viral 1/3 trauma 1/3 unknown
1. Infection
? Infectious condition
- supported by frequent association with current or antecedal illness
- viral or bacterial
- most commonly ENT
- no specific viral antibodies found
2. Trauma
May be contusion of hip
- history of trauma in 30%
3. Allergic hypersensitivity
May be hypersensitivity response
- 25% have atopia
- dramatic response to antihistamines & steroids
Pathology
Culture negative synovial effusion
Synovial hypertrophy 2° to non-pyogenic inflammatory reaction
NHx
Limited duration of symptoms
- average 10 days
- may be 8 weeks
Recurrence uncommon < 10%
Associated with Perthes Disease in 1.5%
- probably not causative
Clinical
Acute onset of unilateral hip pain
- usually hip & groin
- may be thigh & knee
Findings
Limp
Inability to weight bear
Hip held in flexion & ER
Protective muscle spasm
Restricted ROM especially IR
May be low-grade fever < 38°
Blood Tests
May be mild elevation of
- WCC
- ESR
- CRP
Xray
Usually normal
- exclude other conditions
May be mild changes in hip
- coxa magna / femoral neck widening
- ? 2° to hypervascularisation
- not symptomatic
US
May show effusion
Differential Dx
Septic Arthritis
- see Miscellaneous / Infection / Septic Arthritis
- Kocher criteria (WB / ESR / fever / WCC)
Osteomyelitis
Perthes / SUFE / JRA
Management
Important to rule out other pathology
Symptomatic only
- rest in bed and analgesia until FROM shown to decrease recovery time & recurrence
- traction only for severe cases that fail to settle
- NSAID
- PWB on crutches until limp resolves