What is the appropriate diagnosis and treatment approach for a patient presenting with joint pain?

Diagnostic and Treatment Approach for Joint Pain

Begin with plain radiographs of affected joints as the initial imaging modality, combined with targeted laboratory testing including inflammatory markers (ESR/CRP), complete blood count, rheumatoid factor, and anti-CCP antibodies to establish whether inflammatory arthritis is present. 1, 2, 3

Initial Clinical Assessment

Determine the number and pattern of involved joints, duration of symptoms, presence of morning stiffness, and any extra-articular manifestations. 2

Key clinical features to assess:

• Joint distribution: Small joints (MCPs, PIPs, wrists) versus large joints (shoulders, elbows, hips, knees, ankles) 1
• Symmetry: Symmetric involvement suggests rheumatoid arthritis; asymmetric suggests seronegative spondyloarthropathy or psoriatic arthritis 3, 4
• Morning stiffness duration: ≥1 hour strongly suggests inflammatory arthritis 5, 6
• Acute versus chronic onset: Acute monoarticular pain with fever requires immediate arthrocentesis to exclude septic arthritis 2, 3

First-Line Laboratory Investigations

Order ESR and CRP together—both elevated provides the best sensitivity and specificity for inflammatory arthritis. 2, 3

Essential initial labs:

• Complete blood count with differential to evaluate for infection, inflammation, or malignancy 2
• Rheumatoid factor (RF) and anti-CCP antibodies if rheumatoid arthritis is suspected 1, 2, 5
• Serum uric acid if gout is in the differential 7

Imaging Strategy

Plain radiographs are the mandatory first imaging study for all patients with joint pain. 1, 2, 3

Radiographs can demonstrate:

• Erosions, joint space narrowing, and periarticular osteopenia in rheumatoid arthritis 1, 5
• Chondrocalcinosis in pseudogout (CPPD disease) 1
• Tophi and erosions with overhanging edges in gout 1
• Central erosions of interphalangeal joints in erosive osteoarthritis 1

Add ultrasound or MRI only when diagnosis remains unclear after initial workup or to assess early disease activity. 2, 3

• Ultrasound detects synovitis, erosions, and the "double contour sign" in gout with 83% sensitivity 1
• MRI is most sensitive for early erosive changes and bone marrow edema, which predicts radiographic progression 2, 3
• Dual-energy CT complements radiographs for detecting urate deposits in gout 1

Joint Aspiration

Perform arthrocentesis immediately if septic arthritis or crystal-induced arthritis is suspected. 2

Synovial fluid analysis must include:

• Cell count with differential (>50,000 WBC/mm³ suggests septic arthritis) 2
• Crystal analysis under polarized microscopy for monosodium urate (gout) or calcium pyrophosphate (pseudogout) 2
• Gram stain and culture for infectious causes 2

Diagnostic Algorithm for Inflammatory Arthritis

If clinical synovitis is present with elevated inflammatory markers, calculate the 2010 ACR/EULAR classification score for rheumatoid arthritis. 1

Score ≥6/10 confirms rheumatoid arthritis classification:

• Joint involvement: 1-3 small joints = 2 points; 4-10 small joints = 3 points; >10 joints including ≥1 small joint = 5 points 1
• Serology: High positive RF or anti-CCP (>3× ULN) = 3 points; low positive = 2 points 1
• Acute phase reactants: Abnormal CRP or ESR = 1 point 1
• Symptom duration: ≥6 weeks = 1 point 1

Additional Testing Based on Clinical Suspicion

Test for hepatitis B, hepatitis C, and tuberculosis before initiating immunosuppressive therapy. 2, 5

Consider:

• ANA testing if connective tissue disease is suspected (SLE, scleroderma, myositis) 2
• Blood cultures if fever is present or bloodstream infection suspected 2
• HLA-B27 if seronegative spondyloarthropathy is suspected (not routinely recommended) 3

Treatment Initiation

Refer to rheumatology within 6 weeks of symptom onset if inflammatory arthritis is suspected—early aggressive treatment prevents irreversible joint damage. 3, 5

Start methotrexate as first-line disease-modifying antirheumatic drug (DMARD) for confirmed rheumatoid arthritis. 5

• Typical dosing: 7.5-25 mg weekly, escalated over 8 weeks to maximum tolerated dose 1
• Biologic agents (TNF inhibitors like etanercept) are second-line or added for dual therapy if inadequate response 8, 5

Monitoring Strategy

Reassess patients with inflammatory arthritis every 4-6 weeks after treatment initiation using joint counts and inflammatory markers. 2

Target clinical remission defined as: tender joint count ≤1, swollen joint count ≤1, CRP ≤1 mg/dL, and patient global assessment ≤1 on 0-10 scale. 1

Obtain repeat radiographs within 1 year to assess for disease progression. 2

Critical Pitfalls to Avoid

• Do not delay arthrocentesis in acute monoarticular arthritis with fever—septic arthritis is a medical emergency requiring immediate diagnosis and treatment 2, 3
• Do not rely on negative RF alone to exclude rheumatoid arthritis—30% of RA patients are seronegative, and anti-CCP may be positive when RF is negative 1, 5
• Do not order an "arthritis panel" indiscriminately—testing must be guided by clinical suspicion from history and physical examination 7
• Do not assume clinical remission equals true remission—power Doppler activity is found in 15-62% of patients in clinical remission by DAS28 criteria 2