Joint Pathology Flashcards
What should the bones at synovial joints be like?
Fit nicely together with even distribution of pressure
Not touch - separated by cartilage
What type of cartilage is articular cartilage?
Hyaline
What attracts water in cartilage?
Glycosaminoglycans
How is the collagen arranged in articular cartilage?
To hold glycosaminoglycans compressed together
Are there any blood vessels in articular cartilage?
No
How is articular cartilage perfused?
Compression/decompression of cartilage > pushes water in and out
What do the capsule, tendons, and ligaments at the joint do?
Hold everything together
Crucial to joint stability and movement
Where is the synovium?
Lines joint space
Where is the synovium attached?
Firmly anchored to capsule and bone at edges of cartilage
What is the synovium?
Vascular connective tissue with synovial membrane
What are the cell types of the synovium?
25% type A “macrophage-like” synoviocytes
75% type B “fibroblast-like” synoviocytes
Why is the synovial membrane not an epithelium?
No basement membrane
No junctional complexes
What makes up synovial fluid?
Plasma filtrate - easily crosses in and out of joint space
Hyaluronic acid - makes viscous
Lubricin - makes slippery
Etc
How thick is the synovial membrane?
1-4 cell layers
Why is osteoarthritis classified as a degenerative disease?
Cartilage wears away
Does osteoarthritis present symmetrically?
No
When is pain worst in osteoarthritis?
At end of day
What is released by the cartilage matrix and synovial cells in osteoarthritis?
Enzymes - Collagenases - MMPs Cytokines - IL-1
What parts of the joint does osteoarthritis affect?
Capsule
Synovium
Bone
What is the pathophysiology of osteoarthritis?
Damage stimulates chondrocyte - Hypertrophy - Proliferation - Enzyme/cytokine secretion Unravelling of cartilage matrix, release of enzymes, loss of frictionless mechanical function Changes in bone - Thickening - Microfractures Shedding of cartilage - Fibrillation - Erosions Bone-on-bone - Eburnation - Cysts - Osteophytes
What is the morphology of osteoarthritis?
Remaining cartilage looks rough Eburnation of bone Fibrillation of articular cartilage Subchondral cysts Non-uniform loss of cartilage Subchondral thickening Osteophytes
What is eburnation?
Bone looks like ivory
What are osteophytes?
Cartilage growths which become bone through endochondral ossification
How can osteophytes affect the joint?
Can impinge on range of movement/nearby structures; eg: in spine, impinge on nerves
Can improve joint stability
What are the symptoms of osteoarthritis?
Pain - Deep, achy - Worse after activity Onset over years Non systemic symptoms
What are the signs of osteoarthritis?
Reduced range of movement
Crepitus
Osteophytes
What are Bouchard’s nodes?
Osteophytes in proximal interphalangeal joints
What are Heberden’s nodes?
Osteophytes in distal interphalangeal joints
What is the relationship between x-ray and clinical findings in osteoarthritis?
Severity of x-ray findings don’t always correlate with severity of clinical findings
What is subchondral sclerosis?
Bone thicker under damaged cartilage
What are the risk factors for osteoarthritis?
Increasing age
Obesity
Previous injury/abnormality of joint
Repeated heavy use of joint
What is the disease classification of rheumatoid arthritis?
Systemic inflammatory disease
What is rheumatoid arthritis?
Autoimmune attack on connective tissue
What other organs can rheumatoid arthritis affect?
Skin
Blood vessels
Heart
Lungs
What is the primary stimulus in rheumatoid arthritis?
Unknown
Triggered in genetically susceptible individuals
What is the pathophysiology of rheumatoid arthritis?
Self reactive Th1 and Th17 cells activate Secrete cytokines - IL-1 - IL-6 - IL-17 - TNF-alpha Induce - Fibroblasts - Macrophages - Osteoclasts - B cells - T cells - DCs - Mast cells Exuberant granulation tissue-like synovium Collagenases and MMPs Breakdown of cartilage and bone
What is the morphology of the inflammatory changes in the joints in rheumatoid arthritis?
Neutrophils and fibrin may be found in joint space
Mononuclear infiltrate in synovium
- Germinal centres
Hyperplasia of synovium with villus formation
- Pannus
Pannus invades and erodes cartilage and bone
Weakening and destruction of ligaments
What is pannus?
Inflammatory granulation-like tissue in synovium
What are the symptoms of rheumatoid arthritis?
Symmetrical polyarthritis - Usually starts in hands and feet - Distal interphalangeal joints often spared Morning stiffness - Eases with activity Systemic symptoms - Fever - Weight loss - Anaemia
What are the signs of rheumatoid arthritis?
Warm, swollen joints
Rheumatoid nodules
- Common under skin but can get elsewhere
- 30-40% of patients
- Predicts severe disease
Evential destruction and deformity of joints
What does a rheumatoid nodule look like histologically?
Evidence of granulomatous inflammation
Epithelioid macrophages
Lymphocytes and fibrosis
Central necrosis
What do general inflammatory tests show in rheumatoid arthritis?
CRP, ESR, and FBE all show changes of inflammation
What are more specific tests that can be done to diagnose rheumatoid arthritis?
Rheumatoid factor
- Not high specificity and sensitivity
Anti-cyclic citrullinated peptide (anti-CCP) Abs (ACPAs)
- More specific
What is the role of x-rays in diagnosing rheumatoid arthritis?
Little role
What are the risk factors for rheumatoid arthritis?
Genetic
Female
Smoking
Increasing age from 25-55
What is the pathophysiology of gout?
Too much uric acid in body
- Asymptomatic at first
- Eventually precipitates in cool areas with low pH and nucleating agents
- Especially after alcohol/dehydration/dietary indiscretion
Crystals can activate inflammatory cells, synovial cells, and complement
- Acute inflammatory cascade
- IL-1, complement, and chemotaxis > crystals lyse neutrophils
What happens if gout remains untreated?
Progresses into chronic, disabling, tophaceous gout
What is tophaceous gout?
Involvement of multiple joints Recurrent joint inflammation causes damage - Can form pannus Urate deposition in other soft tissue - Forms tophi Gouty neuropathy and kidney stones
What type of inflammation is a gouty tophus?
Granulomatous inflammation (foreign body type)
What are the signs of gout?
Acutely inflamed joint
Seldom systemically unwell
Tophi if chronic
What are the symptoms of gout?
Spontaneous onset of - Excruciating pain - Swelling - Heat - Redness Classically in big toe in early morning
What is the gold standard for diagnosing gout?
Joint/tophus aspiration
- Negatively birefringent crystals with neutrophils
Why is measuring serum urate confusing?
Acute gout attack can lower serum urate
Urate-lowering therapy can precipitate gout
Most people with high urate don’t have gout
What are the risk factors for gout?
Male Increasing age Menopaus Abnormal uric acid metabolism Genetics and ethnicity Obesity Hypertension Metabolic syndrome
