The reasoning
| Feature | Osteoarthritis | Inflammatory |
|---|---|---|
| Age | elderly | younger (RA 30–50) |
| Symmetry | asymmetric | symmetric (RA), asymmetric (seronegative, gout) |
| Joint space loss | non‑uniform (weight‑bearing zone; medial knee, superolateral hip) | uniform/concentric (axial hip migration in RA) |
| Bone density | subchondral sclerosis | periarticular osteopenia |
| Osteophytes | present | absent (RA); proliferative new bone in seronegative |
| Erosions | absent (except erosive OA: central "gull‑wing") | marginal (bare‑area) erosions |
| Cysts | subchondral cysts (geodes) | less prominent |
| Periosteal reaction | absent | seronegative arthritis |
| Loose bodies | present | absent |