2. MSK (Arthritis)

Question 1

Physiological tibial bowing

Answer 1

Smooth, lateral, bilateral, occurs from 18 months to 2 years

Question 2

Pathological causes of Tibial bowing (7)

Answer 2

NF-1: Anterior lateral, unilateral, hypoplastic fibula with psuedoarthritis
Foot deformities: posterior
Hypophosphatasia: Lateral (“Rickets in a newbown”)
Rickets: Lateral, widening and irregularity of growth plates.
Blount: Tibia vara - often asymmetric. Early walking, fat, black child
Osteogenesis imperfecta: Involves all long bones
Dwarfs: Short limbs

Question 3

Arthritis (types) (6)

Answer 3

Degenerative (OA, Neuropathic).
Inflammatory (RA & Variants).
Metabolic (Gout and CPPD)

Question 4

Osteoarthritis - pathophysiology (3)

Answer 4

Commonest arthritis.
Mechanical breakdown –> cartilage degeneration (fissures, microfractures) and fragmentation of subchondral bone (sclerosis and subchondral cysts).

Question 5

Osteoarthritis - imaging (5)

Answer 5

Loss of joint space (not symmetric).
Subchondral cysts
Endplate changes
Vacuum phenomenon
Osteophytes.

Question 6

Neuropathic joint (2)

Answer 6

Buzzword “Surgical like margins”.
Classically shown as bad joint followed by the reason for a bad joint.

Question 7

Neuropathic joint - imaging (5)

Answer 7

Imaging: Deformity with Debris, Dislocation, Dense subchondral bone, Destruction of articular cortex.

Question 8

Erosive osteoarthritis (inflammatory) (3)

Answer 8

“Gull wing” - describes central erosions.
Seen in postmenopausal women.
Favours DIO joints

Question 9

Rheumatoid arthritis (4)

Answer 9

Characterised by osteoporosis, soft tissue swelling, marginal erosions and uniform joint space narrowing.
Often bilateral and symmetric.
Classically spares DIP joints.
Hip: OA tends to affect superior and medial, whereas RA tends to affect axially.

Question 10

RA in the hands (3)

Answer 10

PIP joints involved AFTER MCP joints.
First CMC joint classically spared or last to be involved (OA loves first CMC).

Question 11

RA eponymous syndromes (2)

Answer 11

Felty syndrome: RA > 10 years + splenomegaly + neutropenia
Caplan syndrome: RA + Pneumoconiosis

Question 12

RA variants (4)

Answer 12

Psoriatic arthritis
Reiter’s syndrome (reactive arthritis)
Ankylosing spondylitis
Inflammatory bowel disease

Question 13

Psoriatic arthritis (5)

Answer 13

Affects 30% of psoriasis patients (skin changes usually first).
Strong correlation between nail and DIP involvement.
Classically “Erosive changes with bone proliferation, IP joints > MCP joints”.
Erosions start at margins of joint and move centrally (pencil in cup).
Hands most commonly involved, then feet, then 40% get SI involvement (asymmetric)

Question 14

Psoriatic arthritis buzzwords (6)

Answer 14

Fuzzy appearance to bone around joint (proliferation).
Sausage fingers - soft tissue swelling of fingers.
Ivory phalanx - sclerosis or bone proliferation, most commonly great toe.
Ankylosis in finger
Mouse ears
Acral osteolysis

Question 15

Ankylosis in the hand DDx (5)

Answer 15

RA vs Psoriasis
Symmetric vs asymmetric
Proximal (MCP, carpals) vs Distal (IP joints)
No bone proliferation vs bone proliferation.
Both can cause Mutilans when severe

Question 16

Reactive arthritis (2)

Answer 16

Similar to psoriatic arthritis, with bone proliferation and erosions and asymmetric SI joint involvement.
Reactive arthritis is rare in the hands, prefers feet.

Question 17

Ankylosing spondylitis (8)

Answer 17

Favours spine and SI joints.
“Bamboo spine” due to early syndesmophytes from adjacent vertebral bodies.
“Shiny corners” is a buzzword for early involvement.
Susceptible to trauma.
SI joint usually first involved. Joint widens a bit before narrowing.
Can also get upper lobe predominant interstitial lung disease.
Any ank spond/DISH + minor trauma requires CT whole spine.

Question 18

Ankylosing spondylitis in the hip (4)

Answer 18

If peripheral skeletal involvement, think hip and shoulder. Hip involvement can be very disabling.
Heterotopic ossification occurs after hip replacement or revision, so they often get prophylactic low dose radiation and NSAIDs.
Normal SI joints excludes Ank Spond

Question 19

Inflammatory Bowel Disease - arthritis (2)

Answer 19

2 types
- Axial arthritis: Favours SI joints and spine, often unrelated to bowel disease
- Peripheral arthritis: Varies depending on severity of bowel disease

Question 20

SI joint arthritis - DDx (6)

Answer 20

Unilateral = infection
Asymmetric = Psoriasis or Reiters
- Psoriasis: M = F, also hands, feet, thoracolumbar spine
- Reiters: M>F, feet, lumbar spine
Symmetric = Inflammatory bowel, AS
- AS: M>F, SI joints and whole spine

Question 21

Gout (2)

Answer 21

Crystal arthropathy from deposition of uric acid crystals in and around joints.
Almost always big toe, man, over 40

Question 22

Gout buzzwords/trivia (6)

Answer 22

Earliest sign = joint effusion.
Spares joint space (until late disease).
Juxta-articular erosions occur away from the joint.
Punched out lytic lesions
Overhanging edges
Soft tissue tophi

Question 23

Gout on MRI (2)

Answer 23

Juxta-articular soft tissue mass (low on T2).
Tophus will typically enhance

Question 24

Gout mimickers (5)

Answer 24

Amyloid
RA (Cystic)
Reticular histiocytosis (rarest)
Sarcoid
Hyperlipidaemia

Question 25

CPPD (10)

Answer 25

Calcium Pyrophosphate Dihydrate disease.
Common in older people.
Causes chongrocalcinosis.
Synovitis + CPPD = Pseudogout.
Commonly affects triangular fibrocartilage of the wrist and peri-odontoid tissue and intervertebral disks.
Hooked MCP osteophytes with chondrocalcinosis in the TFCC is classic look.
“Degenerative change in an uncommon joint” - shoulder, elbow, patellofemoral joint, radiocarpal joint.
If isolated patellofemoral, radiocarpal or talonavicular joint disease, think CPPD.
Most commonly affects knees.
Commonly degenerates SL ligament causing SLAC wrist.

Question 26

OA vs CPPD (6)

Answer 26

Many overlapping features:
- Joint space narrowing
- Subchondral sclerosis
- Subchondral cysts
- Osteophyte formation
Unique to CPPD
- Atypical joint distribution (favours compartments like Patellofemoral and radiocarpal).
- Subchondral cysts can be bigger than expected

Question 27

Milwaukee Shoulder (3)

Answer 27

Destruction of shoulder secondary to hydroxyapatite.
Articular surface changes are very advanced, lots of intra-articular loose bodies.
Classically old women with Hx of trauma to the joint.

Question 28

Haemochromatosis (4)

Answer 28

Iron overload causes calcium pyrophosphate deposition, leading to chondrocalconosis.
Similar distribution to CPPD (MCP joints).
Both CPPD and haemochromatosis have hooked osteophytes at MCP joint.
Therapy for systemic disease does not affect the arthritis.

Question 29

Hyperparathyroidism (5)

Answer 29

Can be primary or secondary.
“Subperiosteal bone resorption” of radial aspect of 2nd and 3rd fingers.
“Rugger-jersey spine”
“Brown tumours
“Terminal tuft erosions”

Question 30

Hyperparathyroidism - imaging (5)

Answer 30

Classic imaging:
Superior and inferior rib notching - bone resorption
Resorption along radial aspect of fingers with brown tumours
Tuft resorption
Rugger jersey spine
Pelvis with narrowing or constricting of femoral necks, and wide DI joints.

Question 31

Arthritis - DDx approach (2)

Answer 31

Symmetric joint space narrowing and/or erosions = Inflammatory
Asymmetric joint space narrowing and/or osteophytes = degenerative

Question 32

Inflammatory arthritis - DDx (6)

Answer 32

One joint = infection
Multiple joints:
No bony proliferation, proximal distribution
- RA
Bony proliferation, distal distribution
- AS
- Psoriasis
- Reactive
- Inflammatory bowel related

Question 33

Degenerative arthritis - DDx (5)

Answer 33

Typical joints (hands/knees) = OA
Atypical joint, Atypical age
- Post traumatic
- Gout or CPPD
- Haemophilia
Atypical joint, Atypical age, SEVERE or “Surgical Destruction”
- Neuropathic

Question 34

Spine degenerative change (4)

Answer 34

Usually just multilevel degenerative change in the real world.
Shiny corners or “Flowing syndesmophytes” = AS (early or late).
Bulky osteophytes sparing disc space = DISH
Big, bridging lateral osteophytes = Psoriatic arthritis.

Question 35

Cervical spine changes - DDx (3)

Answer 35

Fusion: either congenital (Klippel-Feil) or Juvenile RA
Erosions of Dens: CPPD or RA
Bad kyphosis: NF1

Question 36

SLE4)

Answer 36

“Reducible joint deformity without articular erosions”
Can show hands with ulnar subluxations at MCPs on Norgaard view, which reduce on AP view because hands are flat.
Increased risk of patellar dislocations.

Question 37

Jaccoud’s arthropathy (3)

Answer 37

Similar to SLE in the hand.
Non-erosive arthropathy with ulnar deviation of 2nd-5th fingers at MCP joint.
Post-rheumatic fever

Question 38

DISH (5)

Answer 38

Diffuse Idiopathic Skeletal Hyperostosis.
Ossification of anterior longitudinal ligament involving more than 4 levels, with sparing of disc spaces.
Thoracic spine most commonly involved.
Often get bony proliferation at pelvis, ischial tuberosities, trochanters and iliac crests.
NO sacroiliitis (different from AS)

Question 39

OPPL (5)

Answer 39

Ossification of the Posterior Longitudinal Ligament.
Associated with DISH, ossification of ligamentum flavum and Ank Spond.
Favours cervical spine of old, asian men.
Can cause canal stenosis and lead to cord injury after minor trauma.
Worse in C spine, usually asymptomatic in thoracic spine

Question 40

Destructive spondyloarthropathy (4)

Answer 40

Associated with renal dialysis patients (>2 years).
Commonly affects C spine.
Looks like bad degenerative changes or CPPD.
Likely caused by amyloid deposition

Question 41

Mixed connective tissue disease (2)

Answer 41

Positive for antibodies (Ribonucleoprotein, RNP).
Serology therefore essential for diagnosis.

Question 42

Juvenile idiopathic arthritis (4)

Answer 42

Age <16.
Washed out hand with proximal distribution and ankylosed carpals (premature fusion of growth plates).
Serology often negative.
Knees: enlargement of epiphyses and widened intercondylar notch, similar to haemophilia

Question 43

Amyloid arthropathy (6)

Answer 43

Seen in dialysis pts and less commonly chronic inflammation such as RA.
Severe pattern of destruction, similar to septic arthritis or neuropathic spondyloarthropathy.
Typically bilateral shoulders, hips, carpals and knees affected.
Common cause of carpal tunnel syndrome.
Joint space usually preserved until late disease.
Common after 10 years of dialysis (80%), rare before 5