Transient synovitis of the hip

Disease Description (Causes and Symptoms)

• Definition: A pediatric hip disorder in which pain and limited joint movement occur due to temporary inflammation of the hip synovium (transient synovitis of the hip).
• Age of onset and epidemiology: Occurs mainly in children aged 3–12 years and is more common in boys.
• Cause (presumed): The exact mechanism is unknown. It often occurs after an upper respiratory tract infection (cold or otitis media) and may be associated with an allergic hypersensitivity reaction or minor trauma.
• Pathophysiology: Nonpurulent inflammation of the synovium increases synovial fluid (joint fluid), causing joint swelling and pain.
• Main symptoms:
  • Pain in the groin or hip area
  • Avoidance of walking or limping (avoidance of weight-bearing)
  • Limited range of motion of the hip (especially limited abduction and internal rotation)
  • A low-grade fever may occur
  • Severe systemic symptoms are rare, and pain is usually mild to moderate

Treatment Methods

• Conservative treatment (standard):
  • Bed rest and restriction of weight-bearing (until the pain subsides)
  • Pain relief with nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen — follow dosing appropriate for the child’s weight and age
  • Gradual resumption of activity and exercise after the rest period (avoid strenuous activity for an additional 1–2 weeks after the pain has resolved)
• Additional examinations and interventions:
  • If ultrasound shows a large amount of joint fluid and the condition is suspected, joint aspiration (diagnostic/therapeutic drainage) may be considered
  • If infection is suspected, such as in the presence of high fever, severe pain, elevated blood test inflammatory markers, or purulent findings on joint aspiration, immediate antibiotic administration and emergency treatment by orthopedics (or pediatric orthopedics) are required — septic arthritis (infectious arthritis) must be ruled out first
• Surgery: Surgery is almost never necessary for transient synovitis itself (if another cause, such as an infectious disease, is identified, the corresponding treatment is performed).
• Precautions (self-care):
  • Monitor pain, walking status, and body temperature, and visit a medical institution immediately if the condition worsens
  • Follow instructions for taking prescribed medication, and watch for gastrointestinal or kidney-related abnormal symptoms when taking NSAIDs

Outpatient Visit Checkpoints (Items to Bring and Example Questions)

• Items/examination materials to bring:
  • A list of currently taken medications (name, dose, and time of administration)
  • Past medical history (especially recent infections and trauma) and allergy history
  • Copies or summaries of previously performed examination results (recent X-rays, ultrasound, blood test results, etc.)
  • Records of when symptoms began, changes in pain intensity, changes in body temperature, and walking status (including whether walking assistance is required at all times)
• Useful information to record for the outpatient visit:
  • When the pain began and its course (how many days it has been present)
  • Whether there was a recent upper respiratory tract infection (cough, runny nose, otitis media, etc.) and its treatment history
  • Factors that worsen the pain (weight-bearing, certain positions, etc.)
• Situations in which an emergency visit is recommended (visit a medical institution immediately):
  • High fever (e.g., 38.5°C or higher) or a fever that continues to rise
  • Sudden worsening with extreme pain or inability to bear any weight at all
  • Severe localized redness, swelling, or skin changes, or systemic symptoms such as decreased consciousness

Examples of General Questions to Ask the Doctor

• "If this is the correct diagnosis, what additional tests are needed?"
• "What are the side effects of this medication (or the prescribed pain reliever)?"
• "How long will it take for the pain to improve, and what is the prognosis?"
• "How specifically should activity be restricted? When can exercise be resumed?"

Examples of Condition-Specific Questions

• "Joint fluid was observed on the ultrasound. Is joint aspiration necessary?"
• "Which blood tests (ESR, CRP, WBC) or imaging tests should be performed first to distinguish this from an infection (septic arthritis)?"

Additional summary (key differential diagnoses and warnings): Transient synovitis usually improves spontaneously within several days to several weeks, but it is important to distinguish it from serious conditions such as septic arthritis, osteomyelitis, and femoral head avascular necrosis (Legg–Calvé–Perthes disease). Fever, severe pain, high inflammatory markers, or inability to bear weight requires immediate evaluation.