Arthritides: Inflammatory and Degenerative

Overview & OA - Joint's Wear & Tear

• Arthritis Types:
  • Degenerative: Osteoarthritis (OA) - most common.
  • Inflammatory: RA, Spondyloarthropathies, Crystal, Septic.
• Osteoarthritis (OA) - "Wear & Tear":
  • Progressive articular cartilage loss; subchondral bone changes.
  • Risk Factors: Age, obesity, joint trauma, genetics.
  • Clinical: Pain (worse with use), morning stiffness (< 30 min), crepitus, ↓ROM.
  • Common Sites: Knees, hips, hands (DIP, PIP, 1st CMC), spine.
• Radiographic Features (OA) 📌 Mnemonic: LOSS:
  • Loss of joint space (asymmetric)
  • Osteophytes (marginal)
  • Subchondral sclerosis
  • Subchondral cysts (geodes)

⭐ Osteophytes are a hallmark of OA, particularly at weight-bearing joints like the knee and hip.

Rheumatoid Arthritis - Fiery Joint Attack

• Chronic, systemic autoimmune disease; symmetrical polyarthritis.
• Targets synovial joints: pannus formation → cartilage/bone destruction.
• Distribution: MCP, PIP (hands/feet), wrists, C-spine. Spares DIPs.
• X-ray:
  • Early: Soft tissue swelling, juxta-articular osteoporosis.
  • Late: Uniform joint space narrowing, marginal erosions ("bare areas"), subluxations, deformities (swan neck, boutonniere).
• 📌 LOPsided EROSION for RA: Loss of joint space, Osteoporosis (juxta-articular), Periarticular swelling, Soft tissue swelling, Erosions (marginal), Deformities, Subluxations.

⭐ Marginal erosions, often at the 'bare areas' (cartilage-free zones), are characteristic of Rheumatoid Arthritis.

Seronegatives - Spine's Twisted Tales

• Group of inflammatory arthritides (HLA-B27 associated, RF negative). 📌 Mnemonic: PAIR (Psoriatic, Ankylosing Spondylitis, IBD-associated, Reactive).
• Common features: Sacroiliitis, enthesitis (inflammation at tendon/ligament insertion), spondylitis (vertebral inflammation).
• Ankylosing Spondylitis (AS):
  • Bilateral, symmetrical sacroiliitis (earliest sign).
  • Romanus lesions (shiny corners), vertebral body squaring.
  • Marginal, thin, vertical syndesmophytes → Bamboo spine; Dagger sign (ossified supraspinous/interspinous ligaments).
• Psoriatic Arthritis (PsA):
  • Often asymmetrical or unilateral sacroiliitis.
  • Bulky, non-marginal, asymmetrical syndesmophytes; paravertebral ossification.
  • Peripheral: Dactylitis ("sausage digits"), "pencil-in-cup" deformity (hands/feet).
• Reactive Arthritis (Reiter's Syndrome):
  • Asymmetrical sacroiliitis.
  • Bulky, non-marginal syndesmophytes, often less extensive than PsA.
  • "Lover's heel" (calcaneal enthesitis/spurs). 📌 Mnemonic: Can't see (conjunctivitis), can't pee (urethritis), can't climb a tree (arthritis).
• Enteropathic Arthritis (IBD-associated):
  • Axial involvement radiographically often resembles AS (bilateral, symmetrical sacroiliitis, syndesmophytes).

⭐ Sacroiliitis is a common early feature in seronegative spondyloarthropathies; bilateral and symmetrical in AS, often unilateral or asymmetrical in PsA and Reactive arthritis. oka

Crystal & Bugs - Joint Invaders

• Gout (MSU)
  • Crystal: Monosodium Urate ($NaC_5H_3N_4O_3$).
  • Radiology:
    • Early: Soft tissue swelling.
    • Late: "Punched-out" erosions, overhanging edges (Martel's sign).
    • Tophi. Joint space preserved late.
  • Site: 1st MTP (podagra).
• CPPD (Pseudogout)
  • Crystal: Calcium Pyrophosphate Dihydrate ($Ca_2P_2O_7 \cdot 2H_2O$).
  • Radiology:
    • Chondrocalcinosis.
    • OA-like changes (radiocarpal, patellofemoral). Hook osteophytes (MCPs).

  ⭐ Chondrocalcinosis (calcification of hyaline or fibrocartilage) is the radiographic hallmark of CPPD.

• Septic Arthritis (Infection)
  • Radiology:
    • Early: Effusion, swelling.
    • Rapid joint space narrowing, juxta-articular osteoporosis.
    • Ill-defined erosions, bone destruction.
  • 📌 SJOE: Swelling → Joint space loss → Osteoporosis → Erosions.

High‑Yield Points - ⚡ Biggest Takeaways

• RA: Symmetrical erosive polyarthritis (MCP, PIP), spares DIPs; periarticular osteopenia.
• AS: Bilateral symmetrical sacroiliitis is hallmark; bamboo spine (syndesmophytes), dagger sign.
• PsA: Asymmetrical arthritis, pencil-in-cup (DIPs), sausage digits, fluffy periostitis.
• OA: Asymmetrical joint space narrowing, osteophytes, subchondral sclerosis & cysts; no erosions.
• Gout: "Rat-bite" erosions (juxta-articular, overhanging edge), tophi; 1st MTP classic.
• CPPD: Chondrocalcinosis in cartilage (knees, wrists) is pathognomonic.
• Reactive Arthritis: Asymmetrical oligoarthritis (lower limb), sacroiliitis, enthesitis.