What is the appropriate work‑up and management for swelling of the left metacarpophalangeal joint?

Left Metacarpophalangeal Joint Swelling: Work-Up and Management

Immediate Clinical Assessment

Begin with visual inspection and palpation to distinguish soft tissue swelling (inflammatory) from bony enlargement (osteoarthritis), as soft tissue swelling indicates synovitis requiring urgent evaluation. 1

Key Physical Examination Findings

• Perform the "squeeze test" by applying lateral compression across the MCP joints—pain indicates inflammatory arthritis and warrants rheumatology referral within 6 weeks 1, 2
• Assess for morning stiffness duration—stiffness lasting >30 minutes strongly suggests inflammatory arthritis rather than mechanical causes 1, 2
• Palpate for joint-line tenderness (tender joint count), which shows moderate interrater reliability (kappa 0.41-0.58) and correlates strongly with MRI-detected synovitis 3
• Visual assessment of swelling demonstrates the highest interrater reliability (kappa 0.55-0.63) and high specificity (>0.8) for detecting synovitis 3
• Examine the pattern of joint involvement—MCP involvement with PIP joints while sparing DIPs suggests rheumatoid arthritis, whereas DIP involvement suggests psoriatic arthritis or osteoarthritis 4, 2

Essential Laboratory Work-Up

Order rheumatoid factor (RF), anti-CCP antibodies, CRP, ESR, complete blood count, comprehensive metabolic panel, and urinalysis immediately without delaying treatment. 2

First-Line Laboratory Tests

• RF and anti-CCP (ACPA) should be ordered simultaneously—anti-CCP has high specificity (90%) with moderate sensitivity (60%), while RF has lower specificity (70%) 2
• CRP is preferred over ESR as it is more reliable, not age-dependent, and better for ongoing monitoring 1, 2
• Complete blood count with differential to assess for cytopenias before starting treatment 2
• Comprehensive metabolic panel including liver function, renal function, glucose, and urate levels 2
• Urinalysis as part of standard initial workup 2

Conditional Testing

• ANA testing if diagnosis remains uncertain or to screen for other connective tissue diseases like lupus 2
• HLA-B27 if symptoms suggest spondyloarthropathy, reactive arthritis, or axial involvement 2
• Hepatitis B, Hepatitis C, and tuberculosis screening before starting any biologic therapy 2

Imaging Studies

Obtain bilateral hand and wrist radiographs at baseline to assess for erosions, which predict aggressive disease and guide treatment intensity. 2

Initial Imaging

• Conventional radiographs show periarticular osteopenia, uniform joint space narrowing, and marginal erosions in inflammatory arthritis versus asymmetric narrowing with osteophytes in osteoarthritis 2
• Presence of erosions on baseline radiographs is highly predictive for RA diagnosis and disease persistence 2

Advanced Imaging When Diagnosis Uncertain

• Ultrasound with Power Doppler is superior to clinical examination for detecting synovitis (75% more accurate than physical examination alone) and should be used when clinical examination is equivocal but suspicion remains high 5, 2, 3
• MRI with IV contrast is more sensitive than ultrasound in early disease and detects bone marrow edema (osteitis), which is the strongest predictor of future erosive progression and functional deterioration 2

Treatment Algorithm

Conservative Management (First-Line)

Start NSAIDs after evaluating gastrointestinal, renal, and cardiovascular status for symptomatic relief while completing diagnostic work-up. 1

• Activity modification and joint protection education through occupational therapy referral 1
• Splinting for joint protection and pain relief 1, 6
• Dynamic exercise programs incorporating aerobic exercise and progressive resistance training, with adequate rest during poorly controlled inflammation 1

Pharmacological Interventions for Inflammatory Arthritis

If inflammatory arthritis is confirmed (score ≥6/10 on ACR/EULAR criteria), start methotrexate 15 mg weekly immediately without waiting for complete serologic work-up, as early treatment prevents irreversible joint damage. 2

• Methotrexate 15 mg weekly as first-line DMARD, with plan to escalate to 20-25 mg weekly 2
• Short-term low-dose prednisone (10-20 mg daily) as bridge therapy while awaiting DMARD effect 2
• Intra-articular corticosteroid injection for localized joint inflammation and painful flares 1
• Target remission (SDAI ≤3.3) or low disease activity (SDAI ≤11) with reassessment every 4-6 weeks 2

Surgical Options (When Conservative Treatment Fails)

Consider surgical intervention when conservative treatments fail to arrest progression of pain or deformity after adequate trial. 7, 6

• Arthroplasty remains the most common treatment option for finger MCP joints, with traditional constrained silicone joint replacements most commonly used 7
• Arthrodesis is indicated for thumb MCP arthritis and is generally reliable 7
• Newer unconstrained surface replacement arthroplasties show promise for osteoarthritis and select inflammatory arthritis cases with good bone stock, minimal deformity, adequate soft tissues, and good disease control 7

Critical Diagnostic Pitfalls

• Do not delay treatment waiting for positive serology—seronegative RA accounts for 20-30% of cases and has similar prognosis to seropositive disease 2
• Do not dismiss inflammatory arthritis based on normal ESR/CRP—acute phase reactants can be normal even in active disease and are poor predictors of RA 2
• Do not rely solely on palpation for swelling assessment—visual inspection has higher reliability and specificity than palpation (kappa 0.19-0.41 for palpation versus 0.55-0.63 for visual assessment) 3
• Consider rare causes such as synovial chondromatosis when common etiologies have been excluded and symptoms persist despite conservative management 8
• Assess for sagittal fiber disruption in patients with chronic pain and swelling following closed crush injury, as partial ulnar sagittal fiber tears may require surgical repair 9

Referral Timing

Refer to rheumatology within 6 weeks of symptom onset if inflammatory arthritis is suspected, as multiple studies demonstrate better outcomes when treatment starts earlier. 2