How to differentiate between additive pain and intermittent pain in pediatric arthritis?

Differentiating Additive vs Intermittent Pain in Pediatric Arthritis

To distinguish additive from intermittent pain patterns in children with arthritis, focus on the temporal evolution and joint involvement: additive pain progressively accumulates across multiple joints that remain symptomatic simultaneously, while intermittent (migratory) pain moves from one joint to another with resolution of previously affected joints over days.

Key Clinical Distinctions

Additive Pain Pattern

• Progressive accumulation: New joints become painful while previously affected joints remain symptomatic, creating an expanding pattern of joint involvement 1
• Persistent involvement: Once a joint becomes symptomatic, it continues to hurt even as additional joints are affected 2
• Typical presentation: Suggests polyarticular juvenile idiopathic arthritis or other chronic inflammatory arthritides where multiple joints are simultaneously inflamed 3
• Duration: Pain persists in affected joints beyond the acute phase, often requiring disease-modifying therapy 2

Intermittent (Migratory) Pain Pattern

• Sequential involvement: Pain moves from one joint to another over days, with previously affected joints improving as new joints become symptomatic 1
• Classic timeframe: The American College of Cardiology states that migratory polyarthritis typically lasts approximately 4 weeks total even without treatment 1
• Joint preference: Large joints are predominantly affected; small joints of hands, feet, and spine are rarely involved, which distinguishes this pattern from other arthritides 1
• Dramatic response: The American Heart Association notes that pain is highly responsive to salicylates and NSAIDs within hours, which is pathognomonic for acute rheumatic fever 1

Practical Assessment Approach

History Taking Essentials

• Temporal mapping: Ask parents and child to map which joints hurt on which days using a calendar or body diagram 2
• NSAID exposure: The American College of Cardiology warns that the migratory pattern may be masked if NSAIDs were given before evaluation, making careful history essential 1
• Pain characteristics: Assess the sensory dimension including quality, intensity, location, and duration at each affected joint 2
• Morning stiffness: Prolonged morning stiffness (>1 hour) suggests inflammatory arthritis with additive pattern rather than migratory acute rheumatic fever 3

Physical Examination Findings

• Joint swelling: Joint swelling and stiffness at rest suggest inflammatory arthritis with additive pattern rather than migratory causes 4
• Warmth assessment: Warm, swollen joints indicate inflammatory arthritis, which typically presents with additive rather than migratory patterns 3
• Sequential documentation: Examine and document all joints at each visit to track whether pain is truly migrating or accumulating 2

Diagnostic Workup Based on Pattern

For Suspected Migratory Pattern

• Streptococcal testing: The American Academy of Pediatrics recommends obtaining throat culture or rapid strep test and anti-streptolysin O (ASO) titers to evaluate for recent streptococcal infection 1
• Jones criteria application: Apply revised Jones criteria for acute rheumatic fever diagnosis, noting that polyarthralgia can be a major criterion in moderate/high-risk populations 1
• Cardiac evaluation: Obtain echocardiogram to evaluate for carditis, as subclinical carditis occurs in 25-50% of acute rheumatic fever cases 1

For Suspected Additive Pattern

• Inflammatory markers: Check ESR, CRP to confirm inflammatory process 3
• Autoimmune screening: Consider ANA, RF testing for polyarticular juvenile idiopathic arthritis 3
• Imaging: Plain radiographs of affected joints to assess for chronic changes 4

Pain Intensity Monitoring Tools

Age-Appropriate Selection

• Ages 4-7 years: Use the Faces Pain Scale-Revised (FPS-R), validated for children ≥4 years 1
• Ages 8+ years: The Visual Analog Scale (VAS) provides scores from 0-100 where 10-30 indicates mild pain, 40-60 moderate pain, and 70-100 severe pain 1, 5
• Chronic pain assessment: The Bath Adolescent Pain Questionnaire (BAPQ) is a multidimensional tool for children ≥8 years with persistent pain 1

Assessment Frequency

• The American College of Rheumatology recommends assessing pain at the first visit and at each subsequent visit at least 7 days apart using developmentally appropriate tools 5
• Serial assessments allow tracking of whether pain is accumulating across joints or migrating between them 2

Critical Pitfalls to Avoid

• NSAID masking: Do not dismiss migratory pattern if child received NSAIDs before evaluation; obtain detailed pre-treatment history 1
• Incomplete joint examination: Failing to examine all joints at each visit may miss the additive nature of polyarticular disease 2
• Underestimating pain impact: Children with persistent additive pain experience significantly more problems with physical, emotional, social, and school functioning than those with acute migratory patterns 6
• Delayed cardiac screening: In migratory patterns suggestive of acute rheumatic fever, failure to obtain echocardiogram may miss subclinical carditis present in 25-50% of cases 1