Arthritides: Inflammatory and Degenerative

Arthritides: Inflammatory and Degenerative

Arthritides: Inflammatory and Degenerative

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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. AS vs PsA Phenotypesoka

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.
FeatureGoutCPPD
CrystalMSU ($NaC_5H_3N_4O_3$)CPPD ($Ca_2P_2O_7 \cdot 2H_2O$)
Radiographic Hallmark"Punched-out" erosions, overhanging edgeChondrocalcinosis
Common Sites1st MTP, ankle, kneeKnee, wrist, MCP joints

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.

Practice Questions: Arthritides: Inflammatory and Degenerative

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Earliest radiographic finding in rheumatoid arthritis

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Flashcards: Arthritides: Inflammatory and Degenerative

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X-ray in gout will show _____ with overhanging margins, and in pseudogout will show chondrocalcinosis

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X-ray in gout will show _____ with overhanging margins, and in pseudogout will show chondrocalcinosis

periarticular erosions

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