Osteoarthritis vs Psoriatic Arthritis
Osteoarthritis and Psoriatic Arthritis are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Osteoarthritis vs Psoriatic Arthritis at a glance
- Osteoarthritis: Non-inflammatory degenerative joint disease driven by progressive articular cartilage loss.
- Psoriatic Arthritis: Seronegative inflammatory arthritis associated with psoriasis; classic features include dactylitis, enthesitis, and DIP involvement.
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Side-by-side comparison
| Feature | Osteoarthritis | Psoriatic Arthritis |
|---|---|---|
| At a glance | Non-inflammatory degenerative joint disease driven by progressive articular cartilage loss. | Seronegative inflammatory arthritis associated with psoriasis; classic features include dactylitis, enthesitis, and DIP involvement. |
| Classic presentation | Heberden nodes (DIP) and Bouchard nodes (PIP); squared first CMC joint; medial knee joint-line tenderness.; Insidious joint pain worse with activity and improved by rest; Brief morning stiffness (<30 minutes) and gel phenomenon after inactivity; Reduced range of motion, crepitus, functional limitation; Knee: medial joint-line pain,… | Joint pain with morning stiffness >30 minutes, improving with activity; Asymmetric oligoarthritis (most common pattern), DIP-predominant, polyarticular RA-like pattern, arthritis mutilans, or axial pattern; Dactylitis — sausage digit from combined tenosynovitis and arthritis; Enthesitis — Achilles, plantar fascia, lateral epicondyle;… |
| Workup / key labs | ACR clinical criteria for knee OA: knee pain plus at least 3 of: age >50, stiffness <30 min, crepitus, bony tenderness, bony enlargement, no palpable warmth. Radiographic hallmarks (Kellgren-Lawrence): joint-space narrowing, subchondral sclerosis, subchondral cysts, marginal osteophytes.; Generally not required for diagnosis when… | CASPAR classification criteria: inflammatory articular disease (joint, spine, or entheseal) plus ≥3 points from psoriasis, nail changes, RF-negative, dactylitis history, and juxta-articular new bone formation.; RF and anti-CCP — typically NEGATIVE (some patients have low-titer positivity); ESR, CRP — variably elevated; can be normal in… |
| Imaging | Weight-bearing plain radiographs of the affected joint — first-line; MRI reserved for atypical presentations, suspected meniscal or ligamentous injury, or possible avascular necrosis; Ultrasound can detect effusion and osteophytes but is not routinely needed | Plain radiographs — 'pencil-in-cup' deformity at DIPs, periostitis, fluffy new bone formation, marginal erosions, ankylosis, asymmetric sacroiliitis, non-marginal syndesmophytes (large, asymmetric, parasyndesmophytes); Ultrasound or MRI — detects enthesitis, synovitis, dactylitis, and bone marrow edema before radiographic change |
| First-line treatment | Patient education and self-management programs; Exercise: low-impact aerobic, strengthening (quadriceps for knee OA), aquatic therapy; Weight loss (5-10% body weight) for knee or hip OA in overweight patients; Topical NSAIDs (diclofenac gel) — preferred initial pharmacotherapy for hand and knee OA; Acetaminophen up to 3 g/day (modest… | Mild peripheral disease: NSAIDs — naproxen, ibuprofen, meloxicam — plus intra-articular steroid injections; Conventional DMARDs for peripheral arthritis: methotrexate, sulfasalazine, leflunomide (also helps skin disease, especially MTX); Treat skin disease in parallel with topical agents and phototherapy as needed |
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