• Chronic inflammation of synovium with erosion in adjacent cartilage/bone
• Multiple joints (symmetrical), typically hands (PIP, MCP), feet (MPL), wrists, knees, elbows, ankles
• Subcutaneous nodules
• Tender, warm, but seldom red
• Morning stiffness, lasting 1hr+
• Low fever common
• Insidious (gradual, cumulative) onset

• Typically seen in Bouchard's node on PIP or Heberden's node on DIP
• Degenaration and progressive loss of cartilage within joints, leading to bone damage and formation of new bone at cartilage margins
• Generally, single joint, but can be additive
• Slowly progressive (insidious)
• Small infusions over joint (especially knee), as well as bony enlargement
• Crepitus over affected joint
• Seldom warm and rarely red
• Stiffness goes away with activity (10-15 minutes in the morning)
• No generalized symptoms

• Severe pain with rapid onset
• Swollen joint, but no trauma
• Fevers, chills, with warm and erythmatous joint
• Generally one joint

• Deposition of urate in joints, leading to inflammation
• Generally in one joint, common in base of the toe (MTP)
  
• Very tender, hot and red
• Onset can be sudden
• Over time, development of multiple sites of inflammation
• Urate crystal deposits can form tophi, swellings with exudate
• Crystals in aspirate are spikey

• Accumulation of calcium pyrophosphate crystals in joint space
• Synovitis, w/ red, tender and warm joints
• Common in knee
• Can occur in multiple joints
• Crystals in aspirate are rhomboid

• Generally seen post-Salmonella, Shigella, Yersinia, Campylobacter, Chlamydia infection
• Skin involvement (Keratoderma blenorrhagieum, circinate balantis) 
• Uveitis, urethritis, arthritis (conjunctivitis)

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• Arthritis typically observed in DIP  
• Sacroiliitis, or spondylitis, var symmetry
• Rash pink, scaly, itchy, on extensor surfaces

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