MSK: Arthritis Flashcards
What are the major categories of arthritis?
- Degenerative
- Inflammatory
- Metabolic
What are the major types of degenerative arthritis?
- Osteoarthritis
- Neuropathic joint
What are the major types of inflammatory arthritis?
- Erosive arthritis (inflammatory osteoarthritis)
- Rheumatoid arthritis
- Rheumatoid variants
What are the “rheumatoid variants”?
- Psoriatic arthritis
- Reactive arthritis (i.e. Reiter’s syndrome)
- Ankylosing spondylitis
- IBD-related arthritis
What are the major types of metabolic arthritis?
- Gout
- CPPD (calcium pyrophosphate deposition disease)
- Hemochromatosis
- Milwaukee shoulder
- Hyperparathyroidism
Think neuropathic joint
Note: “Surgical like margins” of degenerative changes are really only seen in neuropathic joints.
Charcot foot, consistent with neuropathic degenerative changes (common in diabetic neuropathy)
Note: “Rocker-bottom deformity” of the mid foot due to collapse of the longitudinal arch.
What features should make you think osteomyelitis rather than neuropathic degeneration when looking at a diabetic foot radiograph?
- Presence of an ulcer or sinus tract
- Location at pressure points (e.g. metatarsal heads, interphalangeal joints, or posterior plantar aspect of the calcaneus)
Note: Diabetic neuropathic changes (Charcot foot) mostly involves the midfoot.
Gullwing deformity, suggestive of erosive osteoarthritis
Which joints are most classically involved in erosive osteoarthritis?
The distal interphalangeal joints
What are the classic general imaging features of rheumatoid arthritis?
- Marginal erosions
- Uniform joint space narrowing
- Soft tissue swelling
- Osteoporosis
Which joints are classically involved in rheumatoid arthritis?
Metacarpophalangeal joints, with relative sparing of the 1st MCP joint (usually bilateral and symmetric)
Note: RA usually spares the DIP joints (which can help differentiate it from erosive osteoarthritis).
What is the first spot to show rheumatoid arthritis changes in the feet?
The 5th metatarsal head
Isolated degenerative changes of the first CMC joint…
Think osteoarthritis
Note: Rheumatoid and psoriatic arthritis often involve the carpal joints, but these usually spare the first CMC joint until late in the disease.
Rheumatoid arthritis, splenomegaly, and neutropenia…
Felty syndrome
Rheumatoid arthritis and pneumoconiosis…
Caplan syndrome
How can you differentiate osteoarthritis from rheumatoid arthritis in the hip?
The distribution of degenerative changes will be more vertical/horizontal in osteoarthritis
Rheumatoid arthritis mostly affects the superomedial joint space
Which hip is more likely osteoarthritis?
B (vertical forces narrowing the superior joint space)
Note: In A, there is more narrowing of the superomedial joint space, more suggestive of rheumatoid arthritis.
What percentage of pts with psoriasis get psoriatic arthritis?
30%
Which comes first: skin findings or psoriatic arthritis?
Skin findings (90%)
Which joints are most commonly affected in psoriatic arthritis?
Hand joints (mostly interphalangeal joints with relative sparing of the MCP joints)
Note: Feet and SI joints are also commonly involved.
Which portion of a DIP joint is usually involved first in psoriatic arthritis?
The joint margins
Note: The central joint is usually the last to go, which is what creates the pencil-in-cup deformity.
Psoriatic arthritis
Note: Pencil-in-cup deformity and sausage digits.
DIP joint degenerative changes with “fuzzy appearance” to the bone around the joint…
Think psoriatic arthritis
Note: The fuzzy appearance is due to bone proliferation.
Hand arthritis with sausage digits…
Think psoriatic arthritis (due to soft tissue swelling involving an entire finger)
Ivory phalanx, consistent with psoriatic arthritis
Pencil-in-cup deformity, consistent with psoriatic arthritis
Arrows
Finger ankylosis, which can be seen in psoriatic arthritis and erosive osteoarthritis
“Mouse ear” erosions with bony proliferation, consistent with psoriatic arthritis
Acroosteolysis
Note: This can be seen in psoriatic arthritis and other diseases.
Arthritis mutilans (when severe bone resorption leads to soft tissue telescoping/collapse)
Note: This can be seen in severe rheumatoid and severe psoriatic arthritis.
Does psoriatic arthritis tend to be symmetric or asymmetric?
Asymmetric
Note: This can help distinguish it from rheumatoid arthritis, which tends to be symmetric.
Psoriatic and reactive arthritis are both associated with…
HLA-B27
Urethritis, conjunctivitis, and arthritis…
Reactive arthritis (classic triad)
Note: “Can’t see, can’t pee, can’t climb a tree.”
Classic radiographic appearance of reactive arthritis
Very similar to psoriatic arthritis, but rarely involves the hands (reactive arthritis tends to affect things below the waist, e.g. foot joints)
Think early ankylosing sponylitis
Note: “Shiny corners.”
Ankylosing spondylitis
Note: This is the “bamboo spine.”
What is usually the first site to be involved in ankylosing spondylitis?
The sacroiliac joint (symmetric involvement)
Note: The joint actually widens before it narrows.
Next step: Pt with known ankylosing spondylitis has minor trauma to the back
Whole spine CT (bamboo spines are very susceptible to fracture)
What is the most common site of peripheral skeleton involvement in ankylosing spondylitis?
Hips (followed by shoulders)
Pts with ankylosing spondylitis are at a high risk for ______ after hip arthroplasty
Heterotopic ossification
Note: This is why these pts often get postoperative low dose radiation and NSAIDs (as prophylaxis against heterotypic ossification).
Bamboo spine with normal sacroiliac joints…
Its not ankylosing spondylitis (which virtually always involves the SI joints first)
What percentage of pts with IBD get enteropathic arthritis?
20%
What are the two main manifestations of enteropathic arthritis?
- Axial arthritis (favoring the SI joints and spine)
- Peripheral arthritis (which usually varies depending on the severity of the bowel disease)
Symmetric sacroiliitis, think ankylosing spondylitis or enteropathic arthritis
Differential for bilateral sacroiliitis
PAIR:
- Psoriatic arthritis
- Ankylosing spondylitis
- IBD arthritis
- Reactive arthritis
Note: PaiR (psoriatic/reactive tend to be asymmetric) and pAIr (ankylosing and IBD tend to be symmetric).
Unilateral sacroiliitis…
Think infection (e.g. pyogenic, tuberculous, brucellosis)
Note: Psoriatic and reactive arthritis tend to be bilateral (but asymmetric).
Gout is most common in what pt population?
Males over age 40 (think red meat eaters)
Pathophysiology of gout
Uric acid crystal deposition in and around the joints
Most common location for gout
First MTP joint
Earliest sign of gout
Joint effusion
Classic imaging findings for gout
- Juxtaarticular erosions (sparing the joint space until late in the disease)
- Punched out lytic lesions with overhanging edges
- Soft tissue tophi (usually enhances)
Dense soft tissue swelling around the first MTP joint, think Gout
Gout
What are the 5 entities that can have a similar appearance to gouty arthritis?
CRASH:
- Cystic rheumatoid arthritis
- Reticular histiocytosis
- Amyloid
- Sarcoid
- Hyperlipidemia
Note: Gouty appearance is much more rare with these than with actual gout.
Calcium pyrophosphate deposition disease and synovitis…
Pseudogout
Classic imaging feature of CPPD
Chondrocalcinosis (especially of the triangular fibrocartilage)
Note: Hemochromatosis can also appear this way.
Degenerative changes in the shoulder…
Think CPPD (unless there is a reason to develop osteoarthritis)
Note: Degenerative changes in an uncommon joint is a common feature of CPPD.
What is the most common location for CPPD arthropathy?
The knee
Isolated degenerative changes at the STT (scaphotrapeziotrapezoid) joint…
Think CPPD
Note: Consider CPPD when you find degenerative changes in atypical, non-weight bearing joints.
What is the pathophysiology of chondrocalcinosis in hemochromatosis?
Calcium pyrophosphate deposition (same as for CPPD)
Does hemochromatosis arthritis get better after treating the hemochromatosis?
No
Hemochromatosis arthropathy
Note: Uniform MCP joint narrowing favors hemochromatosis. CPPD would look very similar, but the index/middle fingers tend to be more prominently involved than other MCP joints.
Think Milwaukee shoulder (destruction of the humeral head from hydroxyapatite deposition)
Note: Can appear similar to a neuropathic shoulder, but shouldn’t have the same “surgical margins.”
Milwaukee shoulder is more common in what pt population?
Older females with a history of prior shoulder trauma
Subperiosteal bone resorption on the radial aspect of the 2nd and 3rd fingers…
Think hyperparathyroidism
Subperiosteal bone resorption, think hyperparathyroidism
Terminal tuft erosions
Note: This can be seen in hyperparathyroidism.
Rib notching
Note: This can be seen in hyperparathyroidism.
What is the cause of rib notching, rugger jersey spine, and subperiosteal bone resorption in hyperparathyroidism?
Phosphate retention
Severe arthritis in the bilateral hands…
Rheumatoid arthritis
Note: Atlantoaxial instability can occur in rheumatoid arthritis.
Marginal erosions favoring the 4th/5th MCP joints, think rheumatoid arthritis
What should you decide first when looking at complicated hand arthritis radiographs?
Is it inflammatory arthritis (symmetric joint space narrowing OR erosions)
OR
Degenerative (asymmetric joint space narrowing OR osteophytes)
Differential for degenerative changes in an atypical joint or at an atypical age
- Post traumatic
- Gout or CPPD
- Hemophilia
- Neuropathic (if severe or surgical margins)
Bulky osteophytes sparing the disc space…
Think DISH
Flowing syndesmophytes…
Think ankylosing spondylitis (i.e. bamboo spine)
Focal lateral paravertebral ossification/bridging lateral osteophyte…
Think ossification of annulus fibrosis in psoriatic arthritis
Cervical spine fusion, think congenital (Klippel-Feil) or juvenile rheumatoid arthritis
Erosion of the odontoid process, think CPPD or rheumatoid arthritis
Severe cervical kyphosis, think NF1
Classic imaging appearance of DISH
Ossification of the anterior longitudinal ligament involving at least 4 levels with relative sparing of the disc space AND no sacroiliitis (helps distinguish from ankylosing spondylitis)
Ossification of the posterior longitudinal ligament, which can lead to spinal canal stenosis (especially in the cervical spine)
Ossification of the posterior longitudinal ligament is associated with…
- DISH
- Ossification of the ligamentum flavum
- Ankylosing spondylitis
Ossification of the posterior longitudinal ligament is most common in the _____ spine
Cervical
Note: This is not good because this is also where it is most likely to cause spinal stenosis/cord injury.
Pt with end stage renal disease
Think destructive spondyloarthropathy
Note: This is associated with pts on dialysis for at least 2 years due to amyloid deposition (it looks like bad degenerative changes or CPPD).
Think SLE
Note: This is the “swan neck” deformity.
Think SLE
Note: Reversible ulnar deviation.
Classic imaging findings of SLE on hand radiographs
Reducible joint deformities/subluxations without erosions
Pts with SLE have an increased risk of _____ dislocations due to ligamentous laxity
Patella dislocations
History of rheumatic fever
Jaccoud’s arthropathy
Note: Non-erosive arthropahty with ulnar deviation of the 2nd-5th fingers at the MCP joints with a history of rheumatoid arthritis.
Anti-ribonucleoprotein (anti-RNP) positive
Mixed connective tissue disease
By definition, juvenile idiopathic arthritis starts before age…
16
14 y/o
Juvenile idiopathic arthritis
Note: Carpal ankylosis and periarticular osteopenia in a pt younger than 16 y/o.
Does serology help when considering juvenile idiopathic arthritis?
Only in ruling out other diseases (JIA is serology negative 85% of the time)
32 y/o with long standing history of arthritis
Juvenile idiopathic arthritis (chronic)
Note: Epiphyseal overgrowth and severe joint malalignment with a history of arthritis in youth.
Classic imaging features of juvenile idiopathic arthritis
- Carpal ankylosis (due to premature fusion of growth plates)
- Epiphyseal overgrowth
- Widened intercondylar notch in the knee
Widening of the intercondylar notch, think hemophilia or juvenile idiopathic arthritis
Carpal tunnel syndrome in a pt on dialysis…
Think amyloid arthropathy
Amyloid arthropathy is seen in what pt population?
Pts on dialysis for at least 5 years (80% prevalent in pts on dialysis for more than 10 years)
Note: It can also be seen in pts with long-standing chronic inflammation (e.g. rheumatoid arthritis).
Severe destructive arthritis involving the bilateral shoulders, hips, carpals, and knees…
Think amyloid arthropathy (pt likely on dialysis or with long-standing RA)
Widening of the joint space in an adult hip…
Think pituitary gigantism
Note: This is due to the formation of enchondral bone at existing chondrites-osseous junctions.
Think pituitary gigantism
Note: Widening of the hip joint space with epiphyseal necrosis (occurs in gigantism due to the cartilage outgrowing its blood supply).