Distinguishing Rheumatoid Arthritis, Inflammatory Arthritis, and Osteoarthritis

Key Diagnostic Features

The American College of Rheumatology recommends that rheumatoid arthritis (RA) diagnosis is characterized by symmetric small joint involvement with morning stiffness >30 minutes, positive serology (RF/anti-CCP), and systemic inflammation 1.
The European League Against Rheumatism (EULAR) suggests that osteoarthritis (OA) presents with mechanical pain in weight-bearing joints, minimal morning stiffness (<30 minutes), bony enlargement, and normal inflammatory markers 2.
The American College of Rheumatology states that RA is distinguished from OA by the presence of anti-CCP antibodies, which demonstrate 90% specificity with 60% sensitivity, while RF shows 70% specificity with similar sensitivity 1.
The European League Against Rheumatism (EULAR) notes that inflammatory markers such as CRP are preferred over ESR as they are more reliable and not age-dependent, though both can be normal even in active disease 1.

The American College of Rheumatology recommends performing a 28-joint count examination to quantify synovitis, and documenting morning stiffness duration to differentiate between inflammatory arthritis and OA 1, 2.
The European League Against Rheumatism (EULAR) suggests that joint distribution pattern, such as symmetric small joint involvement, suggests RA, while DIP/thumb base involvement suggests OA 1, 2.

The American College of Rheumatology states that RA is characterized by non-proliferative marginal erosions with periarticular osteopenia, while OA is characterized by joint space narrowing, osteophytes, subchondral sclerosis, and cysts 3, 4.

The American College of Rheumatology recommends that patients with RA should be referred to rheumatology within 6 weeks of symptom onset, and treated with methotrexate as first-line therapy, combined with short-term low-dose glucocorticoids 1.
The European League Against Rheumatism (EULAR) suggests that OA management should include non-pharmacologic interventions such as physical activity and exercise, and pharmacologic options such as acetaminophen or NSAIDs at lowest effective dose for shortest duration 5, 6.

The American College of Rheumatology warns against delaying RA treatment waiting for positive serology, as seronegative RA has similar prognosis and requires equally aggressive treatment 1.
The European League Against Rheumatism (EULAR) cautions against dismissing inflammatory arthritis based on normal CRP/ESR, as acute phase reactants are poor predictors and can be normal even in active disease 1.

The American College of Rheumatology recommends referring patients with arthritis involving >1 joint to rheumatology urgently, within 6 weeks of symptom onset 7
The European League Against Rheumatism suggests initiating methotrexate 15-30 mg/week as first-line disease-modifying antirheumatic drug (DMARD) for inflammatory arthritis, with the addition of short-term low-dose prednisone (10-20 mg daily) as bridge therapy while awaiting DMARD effect 8
The American College of Rheumatology recommends a treatment escalation strategy for inadequate response after 3 months, including triple DMARD therapy (methotrexate + hydroxychloroquine + sulfasalazine) or the addition of a biologic agent (TNF inhibitor or IL-6 receptor inhibitor preferred) 8
The American College of Rheumatology suggests using physical activity and exercise programs (aerobic exercise, strength/resistance training) as first-line management for arthrosis/osteoarthritis 9
The American College of Rheumatology recommends using NSAIDs at the lowest effective dose for the shortest duration when inflammation is present in arthrosis/osteoarthritis, and considering intra-articular corticosteroid injections for localized joint inflammation 8
The American College of Rheumatology suggests that disease-modifying agents, such as methotrexate, decrease radiographic progression in rheumatoid arthritis and should be initiated early to prevent bone/joint erosions 10

Cognitive-behavioral therapy has a uniform positive effect on pain in both rheumatoid arthritis and osteoarthritis 9
Patient education programs have a positive effect on pain in osteoarthritis 9