What is the initial step in a comprehensive arthritis workup for a patient with a history of autoimmune disorders or trauma?

Arthritis Workup: Initial Step

The initial step in a comprehensive arthritis workup is a complete history and thorough physical examination to identify clinical synovitis and determine the differential diagnosis ranking, which then guides all subsequent investigations. 1

Critical History Elements to Document

The history must specifically assess:

• Duration of symptoms and morning stiffness (>30 minutes suggests inflammatory arthritis; <1 hour suggests osteoarthritis) 1, 2
• Number and pattern of joints involved (symmetric small joint involvement suggests RA; asymmetric large joint involvement suggests spondyloarthropathy) 1
• Functional status and disability using standardized measures 1
• Age, gender, and geographical area as these influence differential diagnosis 1
• History of trauma (can precipitate localized chronic inflammation that spreads to other joints months later) 3
• History of autoimmune disorders (increases likelihood of inflammatory arthritis and guides autoantibody testing) 1
• Extra-articular/systemic features including rash, fever, dry eyes, oral ulcers, or organ involvement 1, 4

Essential Physical Examination Components

Perform a systematic 28-joint count examination assessing proximal interphalangeal joints (PIPs), metacarpophalangeal joints (MCPs), wrists, elbows, shoulders, and knees for:

• Tenderness and swelling (soft, boggy swelling indicates synovitis; hard, bony enlargement suggests osteoarthritis) 1, 5, 6
• Squeeze test of MCPs and metatarsophalangeal joints (MTPs) to detect clinical synovitis 5
• Range of motion and pain with movement 1, 7
• Axial/entheseal involvement if spondyloarthropathy suspected 1

The presence of definite clinical synovitis in at least one joint not better explained by another disease is the cornerstone finding that determines whether to proceed with inflammatory arthritis workup 5, 6.

Differential Diagnosis Framework

All possible causes must be considered systematically: 1

• Autoimmune (RA, psoriatic arthritis, lupus, Sjögren's)
• Infectious (septic arthritis, Lyme disease, viral arthritis)
• Crystalline (gout, pseudogout)
• Degenerative (osteoarthritis)
• Traumatic (post-traumatic arthritis)
• Metabolic (hemochromatosis)
• Malignancy (paraneoplastic syndromes, metastases)

In patients with history of autoimmune disorders, prioritize testing for connective tissue diseases with additional autoantibody panels beyond RF/ACPA 1. In patients with history of trauma, recognize that severe joint trauma can precipitate chronic localized inflammation that spreads to other joints 2 weeks to 36 months later, manifesting as RA 3.

Immediate Laboratory Testing Based on Clinical Findings

If clinical synovitis is confirmed, order baseline investigations: 1

• ESR and CRP (CRP preferred as it's more reliable and not age-dependent) 1, 5
• RF and ACPA (predictive of RA diagnosis and prognosis; negative tests do not exclude RA) 1, 5, 6
• Complete blood count with differential 1, 5
• Comprehensive metabolic panel (liver function, renal function, glucose, urate) 1, 5
• Urinalysis 1, 5
• ANA and extractable nuclear antigens if connective tissue disease suspected 1, 4

If clinical examination is equivocal but suspicion remains high, proceed directly to ultrasound with Power Doppler or MRI to detect subclinical synovitis before ordering extensive laboratory workup 1, 5, 6.

Baseline Imaging Strategy

X-rays of affected joints should be performed at baseline. 1 For suspected inflammatory polyarthritis, obtain bilateral hand, wrist, and foot X-rays as the presence of erosions is highly predictive for RA development and disease persistence 1, 6.

Repeat X-rays within 6-12 months to monitor for radiographic progression 1, 5.

Advanced Imaging When Diagnosis Uncertain

There is insufficient evidence to recommend routine MRI or ultrasound for all patients, but these modalities should be considered in specific scenarios: 1

• Ultrasound with Power Doppler is superior to clinical examination for detecting synovitis and structural damage, particularly useful when patients don't meet 2010 ACR/EULAR criteria 1, 5, 6
• MRI with IV contrast is more sensitive than ultrasound in early stages and detects bone marrow edema (osteitis), which is the best single predictor of future disease progression 1, 5, 6

Critical Pitfalls to Avoid

Do not delay workup or dismiss inflammatory arthritis based on: 5

• Normal ESR/CRP (acute phase reactants can be normal even in active inflammatory disease; 20-30% of RA patients are seronegative) 5, 6
• Negative RF or ACPA (seronegative RA accounts for 20-30% of cases with similar prognosis) 5, 6
• Absence of radiographic erosions (erosions develop over time; early disease may have normal X-rays) 1, 6

Do not order extensive autoantibody panels indiscriminately. Base additional testing on clinical presentation: 1

• HLA-B27 only if axial/entheseal involvement or spondyloarthropathy suspected 1, 5
• Synovial biopsy only for persistent monoarthritis when diagnosis remains unclear 1

Urgency and Referral Timing

Patients with arthritis involving more than one joint should be referred to rheumatology within 6 weeks of symptom onset, as early treatment prevents irreversible joint damage 1, 5. Initiate diagnostic testing immediately upon presentation, not after referral 1, 5.

Predictors of persistent inflammatory arthritis requiring urgent evaluation: 1

• Disease duration ≥6 weeks
• Morning stiffness >30 minutes
• Involvement of small joints and/or knees
• RF and/or ACPA positivity
• Presence of radiographic erosions
• Elevated ESR or CRP