Arthritis

Question 1

Hallmark of joint inflammation

Answer 1

Bone erosion
- periarticular osteopenia > focal subchondral osteopenia > marginal bone erosion > focal discontinuity of thin, white, subcondral bone plate > enlarges & extends into trabeculae/medullary space

Question 2

Marginal bone erosion

Answer 2

-Bone erosion at the margins of an inflamed synovial joint

=Intra-articulations but not covered by hyaline cartilage

Question 3

Degenerative arthritis

Answer 3

-osteophyte
-bone sclerosis
-non-uniform joint space narrowing
-subchondral cyst
+ no features of inflammatory changes

Question 4

Osteoarthritis

Answer 4

Degenerative joint disease involving a synovial articulation

Question 5

4 features of inflammatory arthritis

Answer 5

1. Periarticular osteopenia
2. Uniform joint space narrowing
3. Soft tissue swelling
4. Bone erosion

Question 6

Phemister triad - tuberculous arthritis

Answer 6

1. Juxtaarticular osteopaenia
2. Peripheral bone erosion
3. Gradual narrowing of joint space

Question 7

Rheumatoid arthritis

-a disease that affects synovium diffusely

Answer 7

• proximal distribution + lack of bony proliferation
• women age 30-60yo
• chronic nature: subluxation, subchondral cyst, ulnar deviation at MCP. Swan neck, Boutonniere deformity
• usually bilateral, symmetrical
• MCP , PIP, mid carpal, radiocarpal, distal radioulnar joints, ulnar styloids
• Foot: lateral aspect of the 5th metatarsal head = first site of bone erosion
• Shoulder: high riding numeral head related to rotator cuff tear

Question 8

Subchondral cyst

Answer 8

= subchondral lucency not interrupting bone surface

Question 9

Kager triangle

Answer 9

• sharply marinated radiolucent triangle on posterior ankle
• Anterior: FHL muscle/tendon
• Posterior: Arrchilles tendon
• Inferior: calcaneus
• Anteroinferior corner = posterior ankle joint
• Posterolaterally: retrocalcaneal bursa

Question 10

Non-ossifying fibromyalgia (>2cm)

Fibrous cortical defect (<2cm)

Answer 10

Features:

• adolescents/young adult
• commonest location: femur, tibia
• did-metaphysical location
• eccentric with mild expansion
• well defined lucent lesion with sclerotic margin
• cortical thinning (but no breach)

-spontaneously regress, asymptomatic

Question 11

Seronegative spondyloarthropathies

Answer 11

• psoriatic, reactive arthritis, ankylosis spondylitis

- inflammation involving multiple joints in a distal distribution of hands or feet with bone proliferation is suggestive

Question 12

RA vs Seronegative spondyloarthropaties

Answer 12

-cartilaginous joints and entheses are involved to a greater extent in SS

Question 13

Psoriatic arthritis

Answer 13

Hallmarks = signs of inflammatory arthritis + bone proliferation, periostitis, enthesitis, distal joint distribution in extremities

• uni/bi-lateral, symmetrical/asymmetrical
• sausage digit: involvement of several joints in a single digit with soft tissue swelling
• bone proliferation: irregular/indistinct appearance to marginal bone (fuzzy, whiskering appearance)
• pencil in cup deformity

Question 14

Reactive arthritis / Reiter syndrome

Answer 14

• Sterile inflammatory arthritis that follows an infection at a different site (commonly enteric/urogenital)
• associated with urethritis, conjunctivitis
• seropositive for HLA-B27 antigen
• young men 25-35yo
• similar radiological features to psoriasis
• different to psoriasis in ‘clinical hx, sex, age, distribution of joint’
• sausage digit and pencil-and-cup may present

Question 15

Ankylosis spondylitis

Answer 15

• 96% patient HLA-B27 positive
• M:F = 3:1, age 20-40yo
• Spine: osteitis, syndesmophyte formation, facet inflammation, facet joint/vertebral body fusion
• SI joint: bilateral & symmetrical, precedes spinal involvement. Starts inferiorly
• Shiny corner sign: erosion at the anterior margin of vertebral body at discovertebral junction > ‘squared vertebral body’ from bone proliferation > thin/slender syndesmophytes (ossification of outer layer of annulus fibrosis) > as syndesmophytes thicken becoming ‘bamboo spine’ > dagger sign (ossification of posterior interspinous ligament) > trolley track sign (dagger sign + fused facet joints)