Osteoarthritis & Other Joint Pathology Flashcards
what is osteoarthritis
destructive disease of synovial joints, which can affect one or more joints and can vary in severity
what are the risks/predisposing factors of osteoarthritis
what is primary osteoarthritis
no predisposing cause
occurs in old age
what is secondary osteoarthritis
underlying abnormality in joint or supporting structures
- hip dysplasia
- rupture of cranial cruciate ligament
- misaligned limb fractures
- angular limb deformities
- aseptic necrosis
- metabolic bone diseases with collapse of subchondral bone, inherited defects in cartilage or collagen formation and septic arthritis
what type of osteoarthritis is common in dogs
secondary to chondrodystrophy, dysplasia or OCD
medium and large breeds most common in major weight bearing joints
what is osteoarthritis in horses
interphalangeal metacarpophalangeal and hock most common
how does osteoarthritis develop
multifactorial condition, but gross and histological changes are similar regardless of cause
non specific lesions; similar across primary and secondary degenerative joint disease
what clinical signs are common in osteoarthritis
joint enlargement or deformity, pain and articular malfunction (reduced range of motion)
what is the pathology of osteoarthritis
first lesions are roughening of the cartilage in areas of weight-bearing –> loss of proteoglycans from the matrix and unmasking of collagen fibrils –> fibrillation
what pathology is seen here
roughening of cartilage in areas of weight bearing
loss of proteoglycans from matrix and unmasking of the collagen fibrils –> fibrillation
what is progressive erosion of fibrillated cartilage accompanied by
sclerosis of the subchondral bone
what is seen here
what is seen here
what is seen here
what occurs in advanced lesions
the articular cartilage may be completely absent and exposed bone polished to a smooth surface by rubbing against the opposing bone –> eburnation
what pathology is seen here
aburnation
what are the processes shown here
normal
fibrillation
eburnation
what is shown here
formation of osteophytes at the margin of articular cartilage and bone
small nodular outgrowth of bone covered by hyaline cartilage
what changes also occur in the joint
thickening of the joint capsule and hypertrophy of synovial villi
what pathology is seen here
thickening of the joint capsule and hypertrophy of synovial villi
what other pathology may occur
rare or low numbers of inflammatory cells may be present
what is the pathology shown here
hypertrophied synovial villi
low numbers of lymphocytes and plasma cells
what lesions can be seen
what lesions are shown here
what lesions are seen
what is the pathogenesis in the development of osteoarthritic changes in joints
- primarily degenerative in nature, accompanying inflammatory changes are secondary
- disruption of balance between degradation and repair cartilage matrix in favour of matrix breakdown leads to loss of proteoglycans and damage to collagen fibrils
- leads to loss of viscoelastic properties of articular cartilage, and further loss of cartilage with biomechanical trauma
what occurs in the balance between synthesis and degradation of cartilage matrix
synthesis: anti-inflammatory cytokines, TIMPs (tissue inhibitor of MMPs), growth factors, collagen synthesis, proteoglycan synthesis
degradation: proinflammatory cytokines, MMPs (matrix metalloproteinases, collagenases, stromelysin, gelatinases), aggrecanases, prostaglandins, nitric oxide
what degrading enzymes lead to the early loss of matrix components
- metalloproteinases
- serine proteinases
- cysteine proteinases
- aggrecanse
why do degradtive enzymes have an effect
natural inhibitors of these enzymes are normally present in articular cartilage but are deficient in degenerative joint disease
what else is involved in the pathogenesis
various cytokines and growth factors –> inflammatory response
IL-1 and TNF-alpha increase the synthesis of metalloproteinases and plasminogen activators and induce the resorption of cartilage
IL-1 also stimulates fibroblasts to synthesize collagen and may contribute to fibrous thickening of joint capsule
what are inflammatory changes secondary to
stimulation of IL-1 and TNF-alpha by synoviocytes following release of degraded collagen and proteoglycan fragments from degenerate cartilage
what is bacterial arthritis
following bacteremia
common in horses and food animals
sequel to neonatal bacteremia
what does bacterial arthritis cause
bacterial lodge in highly vascular synovial membrane
results in polyarthritis
hot, painful swollen joints, destruction of cartilage +/- extension into adjacent bones (osteomyelitis)
spread of infection from nearby soft tissues (uncommon)
how is bacterial arthritis caused
implantation, penetrating wound –> affects one joint, mixed bacterial population
what pathology is seen
fibrinous arthritis in the carpus
abundant yellow fibrin fills the recesses of the joint
articular cartilage is smooth and unaffected
what is seen here
suppurative arthritis
suppurative exudate fills the elbow joint and extends into the surrounding tendon sheaths and soft tissue
suppurative osteomyelitis of the proximal ulna (arrow)
what are common aetiologies of bacterial arthritis
- coliform arthritis (E. coli) –> neonatal septicemia in farm animals
- staphylococcal arthritis (S. aureus) –> common in farm animals and monoarticular arthritis in dogs
- erysipelothrix rhusiopathiae –> causes porcine erysipelas which can result in articular lesions –> erysipelas infection in sheep usually follows cuts or abrasions
- chlamydial arthritis (C. pecorum) –> cause of arthritis in calves and lambs
- mycoplasmal arthritis (M. hypopneumoniae and M. hyosynoviae in pigs, M. bovis in cattle, mycoplasma in sheep)
- borreliosis (lyme disease) –> dogs, multiple joints affected
what is viral arthritis
caprine arthritis-encephalitis virus
what is fungal arthritis
rare with systemic fungal infections (blastomyces, histoplasma, cryptoccocys)
what is immune mediated polyarthritis
inflammatory but not infectious diseases of joints
dogs and cats
divided into erosive polyarthritis/non-erosive polyarthritis based on presence or absence of cartilage destruction
non-erosive polyarthritis –> most common form, see joint effusions with increased neutrophils
no cartilage destruction
idiopathic polyarthritis most common type affecting young sporting and large breeds
most often no known underlying disease
can also secondary to other inflammatory
infectious or neoplastic disease
what is seen here
immune mediated polyarthritis
ex. rheumatoid arthritis
