Joints:

• RA: MCP>PIP, wrist.
• OA: DIP>PIP, spine, hip, knee.
• AnS: sacroiliac joints, neck.

Classic deformities:

• RA: swan neck, ulnar deviation, wrist subluxation, Boutonniere's deformity.
• OA: Heberden's, Bouchard's nodes.
• AnS: neck hyperextension, kyphosis, spinocranial ankylosis.

Morning stiffness:

• RA: >30min.
• OA: <30 min.

ESR:

• RA: increased.
• OA: normal.
• AnS: increased in 50% of pts.

Rheumatoid factor:

• RA: (+) in 70% of pts.
• OA: (-).
• AnS: ? 

NSAID response:

• RA: usually some relief.
• OA: variable relief.
• AnS: variable relief

Treatment:

• RA: OT/PT, NSAIDs, gold, penicillimine, etc.
• OA: paracetamol, weight loss, joint replacement, exercise.
• AnS: exercise instead of rest for backache, NSAIDs.

Imaging:

• RA: juxta-articular osteroporosis, erosions.
• OA: osteophytes, eburnation, reduced joint space.
• AnS: lumbar vertebrae squaring, sacroilitis, bamboo spine.