Overview
Definition:
A limp in a toddler is a symptom of pain or mechanical dysfunction in the lower extremity, leading to an altered gait
Transient synovitis is a common, self-limiting inflammatory condition of the hip joint
Septic arthritis is a bacterial infection of a joint, requiring urgent treatment.
Epidemiology:
Transient synovitis is the most common cause of acute hip pain and limp in children aged 3-10 years, with a peak incidence between 5-8 years
Septic arthritis is less common but more serious, occurring in children of all ages, with a predilection for infants and toddlers (up to 3 years)
It can affect any joint, but the hip is commonly involved.
Clinical Significance:
Differentiating between transient synovitis and septic arthritis is crucial due to the vastly different management and potential sequelae
Missed septic arthritis can lead to rapid joint destruction, osteomyelitis, sepsis, and long-term morbidity, including growth disturbance and functional limitations
Prompt recognition and treatment of septic arthritis are paramount for optimal outcomes.
Clinical Presentation
Symptoms:
Toddler presents with limp, often noticed after mild trauma or illness
Pain is usually localized to the hip, groin, thigh, or knee
Child may refuse to bear weight on the affected leg
Fever may be present, especially in septic arthritis
Red flag symptoms include high fever, severe pain, inability to move the joint, systemic toxicity, and a history of immunocompromise.
Signs:
On examination, the affected hip may be held in slight flexion, abduction, and external rotation to maximize joint volume and minimize pain
Tenderness to palpation over the hip joint
Limited range of motion, particularly internal rotation
Guarding and antalgic gait are evident
In septic arthritis, there may be signs of systemic illness: fever, tachycardia, and irritability.
Diagnostic Criteria:
No specific diagnostic criteria exist for transient synovitis
it is largely a diagnosis of exclusion
For septic arthritis, a combination of clinical signs, laboratory markers (elevated WBC, CRP, ESR), and joint aspiration findings (purulent fluid, positive Gram stain/culture) is used
The Kocher criteria are sometimes used for suspected septic hip in children.
Diagnostic Approach
History Taking:
Detailed history of onset of limp, duration, severity, and provoking factors
Presence and nature of pain (location, radiation, character)
Associated symptoms: fever, chills, rash, upper respiratory infection symptoms
History of recent trauma, insect bites, or skin infections
Immunization status
Previous similar episodes
Red flag symptoms: high fever, inability to bear weight, toxic appearance, rapid onset.
Physical Examination:
Assess gait pattern and weight-bearing
Examine the entire lower extremity, including hips, knees, and ankles
Inspect for swelling, erythema, or warmth
Palpate for tenderness
Assess range of motion of the hip and knee, noting pain and limitations, especially internal rotation of the hip
Check for distal pulses and neurological status
Systemic examination for signs of sepsis.
Investigations:
Laboratory: Complete blood count (CBC) with differential (leukocytosis, neutrophilia), C-reactive protein (CRP) (elevated in infection), Erythrocyte Sedimentation Rate (ESR) (elevated in inflammation/infection)
Imaging: Plain radiographs of the hip and pelvis (may show widening of the joint space or effusion, but can be normal in early septic arthritis)
Ultrasound of the hip (detects joint effusion, thickened synovium, and can guide aspiration)
MRI (gold standard for identifying synovitis, effusion, periosteal reaction, and osteomyelitis, especially if ultrasound is inconclusive or infection is suspected elsewhere)
Joint aspiration: Essential for diagnosis of septic arthritis
Fluid analysis includes cell count and differential, Gram stain, and bacterial culture and sensitivity
A WBC count >50,000/µL with >90% neutrophils is highly suggestive of septic arthritis.
Differential Diagnosis:
Transient synovitis
Septic arthritis
Osteomyelitis
Juvenile idiopathic arthritis (JIA)
Trauma (fracture, sprain, contusion)
Slipped capital femoral epiphysis (SCFE) (older children)
Legg-Calve-Perthes disease
Tumor (rare)
Viral myalgia/arthralgia
Reactive arthritis.
Management
Initial Management:
Urgent evaluation in a healthcare setting is essential
If septic arthritis is suspected, immediate orthopedic consultation and joint aspiration are required
Pain management with analgesics (e.g., paracetamol or ibuprofen)
If transient synovitis is diagnosed, conservative management is initiated.
Medical Management:
For transient synovitis: Rest, analgesia (paracetamol or ibuprofen)
Non-weight bearing on the affected limb is advised
Antibiotics are NOT indicated for transient synovitis
For septic arthritis: Prompt intravenous antibiotics covering common pathogens (e.g., Nafcillin or Cefazolin for Staphylococcus aureus, Ceftriaxone for Gram-negative coverage in older children, Amoxicillin-clavulanate in younger children or if H
influenzae is suspected)
Antibiotic choice should be guided by local epidemiology and Gram stain results, and adjusted based on culture sensitivity
Duration of therapy is typically 2-4 weeks, with transition to oral antibiotics.
Surgical Management:
Septic arthritis: Surgical drainage (arthrotomy or arthroscopy) of the joint is often indicated, especially for hip involvement, to relieve pressure, remove purulent material, and prevent joint damage
This may be combined with or followed by closed suction drainage
Osteomyelitis associated with septic arthritis may also require surgical debridement.
Supportive Care:
For both conditions: Pain control is crucial
Physiotherapy may be beneficial for regaining range of motion after the acute phase, especially for transient synovitis
Close monitoring for signs of complications or treatment failure.
Complications
Early Complications:
Septic arthritis: Joint destruction, osteonecrosis of the femoral head, avascular necrosis, spread of infection to surrounding tissues (osteomyelitis), sepsis, toxic shock syndrome
Transient synovitis: Recurrence of symptoms, although generally benign.
Late Complications:
Septic arthritis: Chronic synovitis, osteoarthritis, joint stiffness, limb length discrepancy, growth disturbances, gait abnormalities, persistent pain
Transient synovitis: Generally no long-term complications
however, repeated episodes can sometimes be mistaken for more serious conditions.
Prevention Strategies:
Prompt diagnosis and treatment of septic arthritis are key to preventing long-term complications
Careful monitoring and follow-up are essential
In transient synovitis, ensuring adequate rest and pain relief can aid recovery.
Prognosis
Factors Affecting Prognosis:
For septic arthritis, prognosis is heavily influenced by the speed of diagnosis and treatment initiation, organism virulence, and promptness and effectiveness of surgical drainage and antibiotic therapy
Delay in treatment significantly worsens prognosis
For transient synovitis, the prognosis is generally excellent.
Outcomes:
With prompt treatment, most children with septic arthritis can achieve a good outcome with minimal long-term sequelae
However, some may experience chronic joint pain, reduced range of motion, or degenerative changes
Transient synovitis typically resolves completely within 1-2 weeks without sequelae.
Follow Up:
Children with septic arthritis require close orthopedic and infectious disease follow-up for at least 6 months to monitor for complications and assess functional recovery
Regular X-rays or MRIs may be needed
Children with transient synovitis should be advised to return if symptoms recur or worsen, and may benefit from review by a pediatrician or orthopedic specialist to confirm the diagnosis.
Key Points
Exam Focus:
Always suspect septic arthritis in a limping child with fever or systemic symptoms
Hip joint effusion on ultrasound or MRI requires urgent aspiration
Differentiate based on inflammatory markers, joint fluid analysis, and imaging
Septic arthritis is an orthopedic emergency requiring immediate surgical drainage and antibiotics.
Clinical Pearls:
Inability to bear weight and hip pain in a toddler are high-alert symptoms
Always perform a thorough examination of the hip
Remember that plain radiographs can be normal in early septic arthritis
Ultrasound is highly sensitive for effusion
Always consider the age of the child and local epidemiology when choosing empiric antibiotics.
Common Mistakes:
Mistaking septic arthritis for transient synovitis due to normal X-rays or a mild presentation
Delaying joint aspiration when septic arthritis is suspected
Inadequate antibiotic coverage for septic arthritis
Not considering other differentials like osteomyelitis or inflammatory arthritis.