Joint Swelling (paediatrics, learning outcomes)

 S5.6

Joint Swelling (diagnosis)

Joint Swelling in Children

1. Define joint swelling in a child and its clinical significance:

• Definition: An increase in fluid within the joint cavity (intra-articular effusion) or thickening of the periarticular soft tissues.
• Significance: It is a non-specific sign occurring in a wide range of conditions—from benign states to serious autoimmune, infectious, or oncological diseases.
• Assessment: Differentiating between intra-articular effusion (characterized by fluctuation, restricted movement, and "patellar tap"/ballottement) and periarticular soft tissue edema.

2. Describe the basic pathophysiological mechanisms of joint swelling:

• Inflammatory Effusion: Increased vascular permeability (e.g., septic arthritis, viral arthritis, autoimmune processes).
• Traumatic Effusion: Bleeding into the joint (hemarthrosis) due to ligament/meniscus rupture or coagulopathy, or reactive exudation.
• Impaired Drainage: Obstruction of lymphatic or venous outflow leading to secondary soft tissue swelling.
• Degenerative Mechanism: Increased production of synovial fluid due to overuse (rare in children).

3. Categorize joint swelling by duration and character:

• By Duration:
  • Acute (hours to days): Often painful; causes include trauma, septic arthritis, reactive arthritis, or hemarthrosis.
  • Chronic (weeks to months): Juvenile Idiopathic Arthritis (JIA), hemophilia, malignancy, or storage diseases.
• By Number of Joints: Monoarthritis (one) vs. Oligoarthritis (2–4) vs. Polyarthritis ($\geq 5$); critical for differential diagnosis.
• By Associated Symptoms: Presence of erythema (redness), spontaneous or palpation tenderness, morning stiffness, and restricted range of motion (ROM).

4. Take a targeted medical history for a child with joint swelling:

• Duration of swelling, type of pain (nocturnal, resting, exertional), preceding trauma, and recent infections (GI, urinary, or respiratory).
• Family history of autoimmune, hematological, or orthopedic diseases.
• Systemic symptoms: Fever, rash (exanthem), anorexia, weight loss, night pain, bleeding tendencies, or skin changes (e.g., erythema migrans in Lyme disease, salmon-pink rash in sJIA).

5. Perform or describe the physical examination of a child with joint swelling:

• Inspection: Symmetry, deformities, skin color, and degree of swelling.
• Palpation: Local temperature (warmth), fluctuation, tenderness, and presence of effusion.
• Range of Motion (ROM): Assess both active and passive restriction.
• Symmetry: Always compare with the contralateral (unaffected) joint.
• Surrounding structures: Examine bursae, ligaments, and tendons.

6. Indicate and interpret laboratory and imaging tests:

• Laboratory:
  • Inflammatory markers: CRP, CBC (Complete Blood Count), ESR (Sedimentation rate).
  • Serology: ASLO (streptococcal), Borrelia, Yersinia, herpes viruses, parvovirus.
  • Immunology: ANA (Antinuclear antibodies).
  • Coagulation studies.
  • Synovial fluid analysis: Cytology, biochemistry, and culture (mandatory if septic arthritis is suspected).
• Imaging:
  • Ultrasound (US): Highly sensitive for detecting effusion and soft tissue changes.
  • X-ray (Skiagram): Usually bilateral for comparison; detects fractures, calcifications, or focal bone lesions.
  • MRI: Detailed visualization of intra-articular and soft tissue structures.

7. Systemic list of causes by etiology (highlighting urgent conditions):

• a) Traumatic: Contusion, sprain (distortion), ligament injury, meniscus rupture, epiphyseal fracture.
  • Hemarthrosis: Trauma or hemophilia.
  • Overuse: e.g., "Juvenile knee" syndromes.
• b) Infectious Arthritis:
  • Acute Bacterial (Septic) Arthritis: MEDICAL EMERGENCY! (Most common: S. aureus).
  • Reactive Arthritis: Post-gastrointestinal, urogenital, or respiratory infections; post-viral (Parvovirus B19, EBV, HBV).
  • Lyme Borreliosis: Most commonly presents as monoarthritis of the knee.
  • Note: Osteomyelitis near a joint can mimic arthritis.
• c) Autoimmune and Inflammatory:
  • Juvenile Idiopathic Arthritis (JIA).
  • SLE, Dermatomyositis, Vasculitis (e.g., Henoch-Schönlein purpura).
  • Rheumatic fever.
• d) Hematological:
  • Hemophilia and other coagulopathies.
  • Leukemia: Often presents with bone pain, night pain, and marrow infiltration.
• e) Mechanical/Orthopedic: Osgood–Schlatter disease, hypermobility syndrome.
• f) Neoplastic:
  • Primary: Bone tumors (Osteoid osteoma, Ewing sarcoma, Osteosarcoma).
  • Secondary: Neuroblastoma, Lymphoma.

8. Describe basic therapeutic principles:

• Etiology-driven:
  • Septic Arthritis: URGENT – I.V. antibiotics + joint aspiration/drainage or surgical washout.
  • Autoimmune: Corticosteroids, DMARDs, or biological therapy.
  • Hemophilia: Replacement of the missing coagulation factor.
• Non-specific (Acute): Rest, elevation, ice (cryotherapy), and NSAIDs.
• Rehabilitation: Physical therapy once acute inflammation subsides.

9. State "Red Flags" indicating a severe condition:

• High fever, severe pain, excruciating joint tenderness, night pain, refusal to walk/weight-bear, or overlying erythema (Septic arthritis).
• Systemic signs of infection or Sepsis.
• Chronic night pain and weight loss (Malignancy).

10. Explain the situation to parents:

• Define the nature of the swelling and potential causes, emphasizing when it constitutes an emergency.
• Explain the importance of timely diagnostics to prevent permanent joint damage.
• Stress the necessity of follow-up and adherence to the prescribed treatment regimen.