What is the most appropriate initial management for a patient with monoarthritis (inflammation of a single joint) in the knee, associated with chest discomfort and an ejection systolic murmur (heart sound), considering options such as aspirin (acetylsalicylic acid) or corticosteroids?

Acute Rheumatic Fever: Aspirin is the Appropriate Initial Management

For a patient presenting with monoarthritis of the knee, chest discomfort, and an ejection systolic murmur, aspirin is the appropriate initial treatment as this clinical triad strongly suggests acute rheumatic fever (ARF), for which high-dose aspirin remains the cornerstone anti-inflammatory therapy for arthritis and carditis. 1

Clinical Recognition of Acute Rheumatic Fever

This presentation is classic for ARF, which requires immediate recognition:

• Migratory monoarthritis or oligoarthritis (often affecting large joints like the knee) combined with cardiac manifestations (chest discomfort, new murmur suggesting valvulitis) points directly to ARF 1
• The ejection systolic murmur likely represents mitral regurgitation from acute rheumatic carditis
• ARF is a post-streptococcal inflammatory condition requiring specific anti-inflammatory management distinct from other forms of arthritis

Why Aspirin Over Corticosteroids

Aspirin is the first-line anti-inflammatory agent for ARF with arthritis and mild-to-moderate carditis: 1

• High-dose aspirin (80-100 mg/kg/day in children, 4-8 g/day in adults divided every 8 hours) provides effective control of both arthritic and cardiac inflammation 1
• Aspirin should be continued until symptoms resolve and inflammatory markers (ESR, CRP) normalize, then tapered gradually 1

Corticosteroids are reserved as second-line therapy in ARF: 1

• Corticosteroids are indicated only for severe carditis with heart failure or when aspirin/NSAIDs fail to control symptoms 1
• The presence of an ejection systolic murmur alone, without evidence of severe cardiac dysfunction, does not mandate corticosteroid use 1
• Starting with corticosteroids when aspirin would suffice exposes the patient to unnecessary risks of long-term steroid toxicity 2

Critical Pitfalls to Avoid

Do not mistake this for simple monoarthritis requiring intra-articular corticosteroids: 2, 3

• While intra-articular corticosteroids are appropriate for isolated knee arthritis from osteoarthritis or other localized inflammatory conditions 2, 3, they are completely inappropriate for ARF
• The systemic nature of ARF (cardiac involvement) requires systemic anti-inflammatory therapy 1

Do not use NSAIDs other than aspirin as first-line: 1

• While other NSAIDs have anti-inflammatory properties, aspirin has the longest track record and most evidence specifically for ARF management 1
• Aspirin provides both anti-inflammatory and analgesic effects needed for ARF 1

Treatment Algorithm

1. Confirm the diagnosis: Obtain throat culture or rapid strep test, ASO titers, anti-DNase B, ECG, and echocardiogram to assess cardiac involvement
2. Initiate high-dose aspirin: 80-100 mg/kg/day (up to 8 g/day in adults) divided every 8 hours 1
3. Monitor response: Continue until symptoms resolve and CRP normalizes, typically 4-6 weeks 1
4. Taper gradually: Reduce dose over 2-4 weeks to prevent rebound inflammation 1
5. Escalate only if needed: Switch to corticosteroids (prednisone 1-2 mg/kg/day) only if severe carditis develops or aspirin fails 1
6. Secondary prophylaxis: Begin penicillin prophylaxis to prevent recurrent ARF

Corticosteroids would be the wrong choice here because they carry significant toxicity risks (bone health, growth impairment in children, metabolic complications) that are not justified when aspirin is effective for this presentation 2, 1.