What are the causes of transient synovitis in pediatric patients?

From the Guidelines

Transient synovitis in pediatric patients is most commonly caused by a viral infection, with the exact mechanism involving an immune response to the viral infection that leads to inflammation of the synovial membrane lining the joint. The condition, also known as toxic synovitis, primarily affects the hip joint in children aged 3-10 years. While the specific virus is often not identified, common culprits include adenovirus, influenza virus, and enteroviruses 1. Less frequently, toxic synovitis may develop following mild trauma or as a reaction to certain medications.

Key Points to Consider

• The inflammatory response in toxic synovitis is self-limiting and rarely causes long-term joint damage, distinguishing it from more serious conditions like septic arthritis, which requires immediate medical intervention 1.
• Common presenting features include a limp, pain, and limited mobility of the affected joint, often following an upper respiratory tract infection.
• The diagnosis of transient synovitis is typically made based on clinical presentation, laboratory tests, and imaging studies, with MRI being useful in differentiating it from septic arthritis 1.
• The condition typically resolves spontaneously within 1-2 weeks with supportive care, including rest and anti-inflammatory medications such as ibuprofen (10 mg/kg/dose every 6-8 hours) or naproxen (5-7 mg/kg/dose twice daily) 1.

Important Considerations for Management

• Early diagnosis and differentiation from septic arthritis are crucial to prevent unnecessary treatments and potential complications 1.
• Imaging studies, including ultrasound and MRI, can be helpful in diagnosing and managing transient synovitis, especially in cases where the diagnosis is uncertain or when there are concerns about potential complications 1.
• The use of antibiotics is not recommended for the treatment of transient synovitis unless there is a clear indication of a bacterial infection 1.

From the Research

Causes of Transient Synovitis in Pediatric Patients

The causes of transient synovitis in pediatric patients are not fully understood, but several factors have been identified:

• Unknown etiology, although a recent history of an upper respiratory tract infection may be present in some cases 2
• May be related to a viral or bacterial infection, but the exact mechanism is unclear 3, 4
• Can be distinguished from more serious entities such as septic arthritis, osteomyelitis, and pyomyositis through diagnostic testing and evaluation 3, 4
• Lyme arthritis is another potential cause of hip pain in pediatric patients, and can be similar in presentation to transient synovitis and septic arthritis 5

Risk Factors and Associations

Several risk factors and associations have been identified:

• Age: younger children are more likely to be misdiagnosed with transient synovitis when they actually have a bacterial musculoskeletal infection 3
• Recent upper respiratory tract infection: may be present in some cases of transient synovitis 2
• Geographic location: Lyme arthritis is more common in certain areas, and can be a cause of hip pain in pediatric patients 5

Diagnostic Considerations

Diagnostic considerations for transient synovitis include:

• Laboratory tests: such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) 3, 5
• Imaging studies: such as ultrasound and radiographs 2, 3
• Clinical evaluation: including assessment of pain, limping, and refusal to bear weight 4, 5