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 arthropathy is suspected. 2, 3

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

Rheumatoid Arthritis Classification

Use the 2010 ACR/EULAR criteria requiring a score ≥6/10 for definite RA classification. 1

Scoring system:

• Joint involvement: 1 small joint = 2 points; 4-10 small joints = 3 points; >10 joints with ≥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

Order ANA testing only if connective tissue disease features are present (malar rash, photosensitivity, serositis, oral ulcers). 2

Obtain blood cultures if fever is present or acute onset suggests bloodstream infection. 2

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

Critical Red Flags Requiring Urgent Action

• Fever with acute monoarticular swelling: Perform immediate arthrocentesis 3
• Sinus tract communicating with a prosthetic joint: Definitive prosthetic joint infection 8
• Purulence around prosthesis: Definitive prosthetic joint infection 8

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

Methotrexate is the first-line disease-modifying antirheumatic drug for rheumatoid arthritis. 5

Biologic agents (TNF inhibitors like etanercept) are second-line or added for dual therapy with methotrexate. 9, 5

Follow-Up Monitoring

Monitor patients with inflammatory arthritis every 4-6 weeks after treatment initiation using serial examinations and inflammatory markers. 2

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

Treatment targets:

• Clinical remission defined as: Tender joints ≤1, swollen joints ≤1, CRP ≤1 mg/dL, and patient global assessment ≤1 on 10-cm scale 1
• Alternative remission criterion: SDAI score ≤3 1

Common Pitfalls to Avoid

Do not rely on a negative RF alone to exclude rheumatoid arthritis—30% of RA patients are seronegative, and anti-CCP may be positive when RF is negative. 5

Do not order an "arthritis panel" indiscriminately—testing should be guided by specific clinical findings from history and examination. 7

Do not delay arthrocentesis in acute monoarthritis—septic arthritis is a medical emergency requiring immediate diagnosis and treatment. 2, 3

Recognize that power Doppler activity on ultrasound is present in 15-62% of patients in clinical remission by DAS28 criteria—subclinical inflammation may persist despite apparent clinical improvement. 2