Hip Transient Synovitis

  • Transient synovitis is characterized by the acute onset of monarticular hip pain, limp, and restricted hip motion.
  • It must be distinguished from septic arthritis.
  • Gradual but complete resolution over several days to weeks is the norm.
  • Synonyms: Toxic synovitis; Irritable hip
  • Transient synovitis is the most common cause of hip pain in children.
  • It is a diagnosis of exclusion.
  • Transient synovitis of the hip can occur from 9 months of age to adolescence; most cases occur in children 3-8 years old.
  • The risk of a child having at least 1 episode of transient synovitis of the hip is 1-3%.
    • This risk is 3 times greater in patients with a stocky or obese physique.
  • Right and left involvement is essentially equal; concurrent bilateral involvement has not been reported.
  • Male:Female ratio is 2:1.
  • Transient synovitis accounts for 0.5% of annual pediatric orthopaedic admissions.
  • The incidence is much lower among African Americans.
Risk Factors
  • Male gender
  • Upper respiratory infection or other active infection
This condition is not genetic.
  • The true cause is unknown; it appears to be an immune-mediated inflammation, not an infection.
  • It has been proposed that transient synovitis of the hip may be associated with active infection elsewhere, trauma, or allergic hypersensitivity.
  • Nonspecific upper respiratory infection, pharyngitis, and otitis media have been associated with the occurrence of transient synovitis in as many as 70% of cases.
  • An association is noted with minor trauma in up to 30%, and with allergic predisposition in up to 25%.
Associated Conditions
Legg-Calve-Perthes disease (~1.5%)


Signs and Symptoms
  • An acute onset of unilateral hip pain occurs in an otherwise healthy child.
  • Pain usually is confined to the ipsilateral groin and hip area, but it may present as anterior thigh and knee pain.
  • Limp and antalgic gait are common, with some patients refusing to bear weight on the involved extremity.
  • The hip is held in a flexed and externally rotated position and has restricted ROM.
  • The patient may have a low-grade fever.
  • Laboratory values are nonspecific and are often within normal limits.
Physical Exam
  • The patient usually indicates unilateral hip pain confined to the ipsilateral groin, anterior thigh, or knee.
  • ROM often is decreased and painful.
  • The patient does not have as much pain as a patient with a septic hip.
    • If the hip ROM is tested slowly, it is usually at least 50% of normal.
  • While walking, patients often display a limp or an antalgic gait; some children refuse to walk.
  • Ipsilateral muscle atrophy is seen rarely, but when present, it implies a longstanding duration of symptoms, and a diagnosis other than transient synovitis should be considered.


  • Results are usually nonspecific and within normal limits, but they may help to rule out other diagnoses.
    • The peripheral white blood cell count is normal to slightly elevated.
    • The ESR averages 20 mm/hour but may be slightly higher.
    • Urinalysis, blood culture, rheumatoid factor, and Lyme titers and tuberculin skin test results are usually within normal limits.
    • Analysis of joint fluid for complement levels or other tests has been nonspecific.
  • Radiography:
    • Plain films of the hip should include AP and lateral views.
  • In transient synovitis, these films are normal but may help rule out other diagnoses, such as Legg-Calve-Perthes disease and SCFE.
  • Ultrasound may be useful to determine if an effusion exists, and to guide aspiration, if infection cannot be ruled out clinically.
  • MRI is needed only in cases of persistent pain, when infection has been excluded.
  • A bone scan often is not helpful because this condition is not a bony process.
Pathological Findings
  • Biopsy specimens have shown synovial hypertrophy secondary to nonspecific, nonpyogenic inflammatory reaction.
  • Hip joint aspirates have shown a culture-negative synovial effusion, usually 1-5 mL.
Differential Diagnosis
  • Transient synovitis of the hip is a diagnosis of exclusion.
  • Conditions to rule out include:
    • Pyogenic arthritis
    • Osteomyelitis in the adjacent femoral neck or pelvis
    • Tuberculous arthritis
    • Psoas abscess
    • Other muscle infection about the hip
    • Juvenile rheumatoid arthritis
    • Acute rheumatic fever
    • Legg-Calve-Perthes disease
    • Tumor
    • SCFE
    • Dislocation
    • SI joint infection


General Measures
  • Transient synovitis usually has a limited duration of symptoms, averaging <7 days.
    • Most studies report complete resolution of all signs and symptoms with no immediate residual clinical or radiographic abnormalities.
    • Long-term studies have shown mild radiographic changes in the involved hip.
  • Traction and routine joint aspiration are not always needed.
    • If traction is used, it is to promote rest and comfort.
    • The hip should be in ~30° of flexion to avoid increasing intra-articular pressure.
  • The important point in management of this condition is to establish the diagnosis: Pyogenic arthritis must be excluded, on clinical grounds or with laboratory tests.
  • Treatment is directed at rapidly resolving the underlying inflammatory synovitis with its symptoms.
  • Bed rest until initial acute pain resolves
  • Weightbearing after pain resolves and full ROM returns, followed by a period of refraining from strenuous activities

Special Therapy

Physical Therapy
  • Usually not necessary
  • Parents can moderate child’s activity adequately.
First Line
  • Anti-inflammatory drugs:
    • Some experts believe these medications should be withheld to avoid masking an infection, but others believe they may have diagnostic value in speeding the natural resolution of inflammatory symptoms.


The prognosis is good because transient synovitis is self-limiting, without any clinically significant sequelae.
  • 1 study has reported that Legg-Calve-Perthes disease or AVN of the femoral head may develop several months after an episode of transient synovitis of the hip.
    • This finding probably represents a delay in establishing the correct diagnosis.
Patient Monitoring
  • A physician should be available for re-evaluation at all times until the possibility of infection is excluded.
  • The child should be re-examined in ~1-2 weeks to determine return of motion before resuming full weightbearing and normal activity.
  • Parents should bring the child back if symptoms recur or increase.


727.0 Synovitis
Patient Teaching
  • Transient hip synovitis is a self-limiting process without major consequences.
  • Some authorities have suggested an increased incidence of later Legg-Calve-Perthes disease in such patients, but this finding has not been proven conclusively.


Q: Do all patients with transient synovitis require aspiration of the hip?
A: No. Although the essence of management is to rule out infection, in many cases this goal can be accomplished clinically by noting that transient synovitis involves a more mild degree of guarding, more mild elevation of infection and inflammatory markers. Most often, patients with transient synovitis will be able to bear some weight on the involved side.
Q: If aspiration is needed to rule out infection, where and how should it be done?
A: Aspiration requires sedation. It should be done with imaging (ultrasound or fluoroscopy) to be certain that the aspirate is from the hip joint. A radiologist or orthopaedic surgeon may perform this procedure. Anterior, medial, or lateral approaches are used. Fluid should be sent for cell count with differential and culture.


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