Joint disease/arthritis Flashcards
Outline types of joints
Joints are connections between bones
–Synovial joints- movable joints of the body
(knee joint)
–Non synovial joints- structural integrity and minimal movement
•Cartilaginous (e.g., intervertebral disks)
•Fibrous (e.g., cranial sutures)
List structures of synovial joints
Articular surface is covered by hyaline cartilage (Healing is poor)
–Articular cartilage: acts as a shock absorber between bones
•Chondrocytes produce the matrix + enzymes and cytokines to degrade it
•Collagen II
•Proteoglycans
•H2O
- Joint capsule (pain sensitive) lined by synovium
- Ligaments- band of fibrous connective tissue
- Bursa- fibrous sac that acts as a cushion to ease movement in areas that are subject to friction
- Synovial membrane and synovial fluid
Describe synovium
The synovium aka synovial membrane lacks a basement membrane-> quick exchange between blood and synovium
–Type A synovial cells are macrophage-like (phagocytic and produce hyaluronic acid)
–Type B synovial cells (fibroblast-like)->protein
Describe synovial fluid
Synovial fluid located in synovial cavity (lubrication and nourishment for cartilage)
- Colour - colourless to pale yellow
- Clarity- transparent
- WBC/mm3 < 200
- PMNs < 25%
- Glucose nearly equal to blood
- Gram stain negative
Classify arthritis
- Osteoarthritis
- Arthritis related to infectious agents
- Arthritis related to immunological disease
- Arthritis induced by crystals
- Arthritis associated with systemic disease
Osteoarthritis
most common type of rheumatic disease
Degenerative disease characterised by progressive erosion of articular cartilage affecting 80% of elderly
classified as primary or secondary
Non inflammatory process of arthritis
osteoarthrosis
Define primary osteoarthritis
•Primary (idiopathic)
–Affects elderly
–Involves the weight-bearing joints (e.g., hips and knees)
•More common in overweight
–Interphalangeal joints
–Some families have mandelian pattern of inheritance of primary generalised osteoathritis (mutation in the gene for type II collagen)
Define secondary osteoarthritis
•Develop at any age in a damaged joint –Trauma –Rheumatoid arthritis –Gout –Tuberculosis –Acromegaly –Haemochromatosis –Deformity (e.g., dislocation of the hip)
PATHOGENESIS OF OSTEOARTHRITIS
•Aging and mechanical effects “wear and tear”
•Biomechanical stresses of weight bearing over time
•Genetic factors
•Changes in the composition and the mechanical properties of cartilage
–Increased water and decreased concentration of proteoglycans
–Chondrocytes produce IL1, TNF-α and nitric oxide
•Stimulate production of metalloproteinase that degrade the matrix
•Inhibit production of type II collagen and proteoglycan
Morphology of osteoarthritis
Destruction of articular cartilage
–Chondromalacia
–Cartilage fibrillation
–Erosion
Exposure of subchondral bone plate
–Subchondral sclerosis (eburnation, ivory)
–Cyst formation
–Small fractures
•Osteophyte formation (lipping) outward growth of bone at the margins of articular surfaces;;
Formed by enchondral ossification
•Joint mice (detached fragments of bone)-> pain and recurrent locking
•Osteoporosis
Secondary changes •Thickening of the synovium with minimal inflammation •Atrophy of the muscle •Deformity of the joint –Osteophyte formation –Subluxation (partial dislocation) •Osteoporosis
Explain osteophyte formation in osteoarthritis
- Heberden’s nodes are osteophytes producing palpable enlargement at the distal interphalangeal joints and often an early manifestation of osteoarthritis
- Bouchard nodes are similar but on the proximal interphalangeal joints
Clinical features of osteoporosis
•Asymptomatic •Symptomatic –Severe pain –Morning stiffness –Restricted movement –Crepitous –Compression of nerve root by osteophytes –Deformity
Investigations a/w osteoarthritis
•X-ray •Negative serology (exclude RA) •Synovial fluid aspirate –Synovial fluid is clear and viscous –Cell count is slightly raised or normal
Tx for osteoarthritis
Glucosamine and chondroitin, s adenosylmethioninine
Define RA
Autoimmune systemic disorder that affects many organs especially (joints, skin, heart, lungs, eyes, lymph nodes and marrow)
•Affects 3% of women and 1% of men
•Most cases arise in young or middle-aged females
•Course unpredictable
–Insidious
–Remittent
CRITERIA FOR RHEUMATOID ARTHRITIS
Four or more of the following –Morning stiffness –Arthritis of three or more joints –Arthritis of the hands –Symmetrical arthritis –Rheumatoid nodule –Serum rheumatoid factor –Characteristic x-ray findings
Pathogenesis for RA
Genetic susceptibility
•Associated with HLADR4
•30% concordance between monozygotic twins
Autoimmune reaction
•Type IV hypersensitivity (CD4+ T-cells)
•Autoantibodies ( B-cells)
•Cytokines (IL-1 and TNF) injury
Microbial agent •? Parvovirus, mycobacteria, mycoplasma •? EBV –EBV detected in synovium –EBV and type II collagen share similar epitopes –B cell infected by EBV RF
Describe rf
•80% patients with rheumatoid arthritis
•IgM antibody against the FC portion of the IgG
•Titre correlates with severity of disease
•RF-IgG immune complexes
–Synovial fluid and synovial membrane
–Circulating immune complexes-> extra-articular manifestations
•Present in < 5% of normal elderly
Morphology of RA
Classically affects the SYNOVIUM of small joints of hands especially
– Proximal interphalangeal joints (swan-neck deformity, boutonniere deformity, ulnar deviation of fingers)
–Metacarophalangeal (radial deviation of wrist)
•Symmetrical
•Polyarticular
Secondary changes
- affects joints
- osteoarthritis
- osteoporosis
- muscle wasting
