Causes of Migrating Polyarthritis with Knee Effusion in Drug Users
In drug users, migrating polyarthritis with knee effusion is most commonly caused by infectious processes, particularly infective endocarditis with septic emboli, or by reactive arthritis following bacterial infections.
Infectious Causes
Infective Endocarditis
- Most common serious cause in IV drug users
- Characterized by:
- Migratory joint pain affecting multiple joints
- Knee effusion (often with inflammatory characteristics)
- Associated symptoms: fever, heart murmurs, petechiae, Osler nodes
- Causative organisms:
- Staphylococcus aureus (most common in IV drug users)
- Streptococcal species
- Gram-negative organisms
Septic Arthritis
- Direct joint infection that can present with effusion
- Often affects a single joint but can be polyarticular in:
- Disseminated gonococcal infection
- Disseminated bacterial infection in immunocompromised hosts
- Requires urgent diagnosis and treatment to prevent joint destruction
Reactive Arthritis
- Follows bacterial infections (often GI or GU tract)
- Classic triad: arthritis, conjunctivitis, urethritis
- Can present with migratory pattern before settling in larger joints
- Associated with HLA-B27 in many cases
Rheumatic Fever
- Can present with migratory polyarthritis and effusion
- Associated with prior streptococcal infection
- According to the Jones criteria, polyarthritis is a major criterion for diagnosis 1
- Highly responsive to salicylates and NSAIDs
- More common in areas with high incidence of rheumatic fever
Drug-Related Causes
Direct Drug-Induced Arthritis
- Certain substances can directly cause inflammatory arthritis 2
- Examples:
- Cocaine (vasculitis with joint manifestations)
- Opioid contaminants
- Adulterants in street drugs
Withdrawal Syndromes
- Opioid withdrawal can present with diffuse arthralgias
- May be confused with inflammatory arthritis
HIV-Associated Arthritis
- Common in IV drug users with HIV
- Can present as:
- HIV-associated arthritis
- Reactive arthritis
- Psoriatic arthritis
Systemic Inflammatory Conditions
Seronegative Spondyloarthropathies
- Can present with migratory pattern and knee effusion
- Includes:
- Psoriatic arthritis
- Reactive arthritis
- Enteropathic arthritis
- Often associated with skin manifestations or GI symptoms 3
Vasculitis
- Polyarteritis nodosa can present with polyarthritis and skin lesions 4
- More common in hepatitis B/C infected individuals (common in IV drug users)
Diagnostic Approach
Joint Fluid Analysis
- Essential for distinguishing infectious from non-infectious causes
- Parameters to assess:
- Cell count and differential (>50,000 WBC/mm³ suggests infection)
- Gram stain and culture
- Crystal analysis to rule out gout/pseudogout
Blood Tests
- Blood cultures (multiple sets)
- Inflammatory markers (ESR, CRP)
- Serologic tests for:
- HIV, hepatitis B/C
- Anti-streptolysin O titers
- Rheumatoid factor and anti-CCP antibodies
Imaging
- Ultrasound can identify effusions and guide aspiration 5
- MRI may be necessary to evaluate for osteomyelitis or soft tissue infection
Treatment Priorities
For Suspected Infection
- Immediate joint aspiration
- Empiric antibiotics pending culture results
- For endocarditis: blood cultures and echocardiography
For Non-Infectious Inflammatory Arthritis
- NSAIDs are first-line for inflammatory arthritis with effusion 5
- Intra-articular corticosteroid injection for persistent effusion 1, 5
Important Considerations
- Never delay diagnosis of septic arthritis or endocarditis in drug users
- Always consider infectious causes first due to high mortality if untreated
- Address underlying substance use disorder as part of comprehensive management
- Consider co-infections (HIV, hepatitis) that may complicate diagnosis and treatment
Red Flags Requiring Urgent Attention
- High fever
- Rapidly progressive joint destruction
- Multiple joint involvement with systemic symptoms
- Evidence of cardiac involvement (new murmur, heart failure)
- Skin lesions suggesting endocarditis (Janeway lesions, Osler nodes)