Osteoarthritis & Other Joint Pathology

Question 1

what is osteoarthritis

Answer 1

destructive disease of synovial joints, which can affect one or more joints and can vary in severity

Question 2

what are the risks/predisposing factors of osteoarthritis

Answer 2

Question 3

what is primary osteoarthritis

Answer 3

no predisposing cause

occurs in old age

Question 4

what is secondary osteoarthritis

Answer 4

underlying abnormality in joint or supporting structures

1. hip dysplasia
2. rupture of cranial cruciate ligament
3. misaligned limb fractures
4. angular limb deformities
5. aseptic necrosis
6. metabolic bone diseases with collapse of subchondral bone, inherited defects in cartilage or collagen formation and septic arthritis

Question 5

what type of osteoarthritis is common in dogs

Answer 5

secondary to chondrodystrophy, dysplasia or OCD

medium and large breeds most common in major weight bearing joints

Question 6

what is osteoarthritis in horses

Answer 6

interphalangeal metacarpophalangeal and hock most common

Question 7

how does osteoarthritis develop

Answer 7

multifactorial condition, but gross and histological changes are similar regardless of cause

non specific lesions; similar across primary and secondary degenerative joint disease

Question 8

what clinical signs are common in osteoarthritis

Answer 8

joint enlargement or deformity, pain and articular malfunction (reduced range of motion)

Question 9

what is the pathology of osteoarthritis

Answer 9

first lesions are roughening of the cartilage in areas of weight-bearing –> loss of proteoglycans from the matrix and unmasking of collagen fibrils –> fibrillation

Question 10

what pathology is seen here

Answer 10

roughening of cartilage in areas of weight bearing

loss of proteoglycans from matrix and unmasking of the collagen fibrils –> fibrillation

Question 11

what is progressive erosion of fibrillated cartilage accompanied by

Answer 11

sclerosis of the subchondral bone

Question 12

what is seen here

Answer 12

Question 13

what is seen here

Answer 13

Question 14

what is seen here

Answer 14

Question 15

what occurs in advanced lesions

Answer 15

the articular cartilage may be completely absent and exposed bone polished to a smooth surface by rubbing against the opposing bone –> eburnation

Question 16

what pathology is seen here

Answer 16

aburnation

Question 17

what are the processes shown here

Answer 17

normal

fibrillation

eburnation

Question 18

what is shown here

Answer 18

formation of osteophytes at the margin of articular cartilage and bone

small nodular outgrowth of bone covered by hyaline cartilage

Question 19

what changes also occur in the joint

Answer 19

thickening of the joint capsule and hypertrophy of synovial villi

Question 20

what pathology is seen here

Answer 20

thickening of the joint capsule and hypertrophy of synovial villi

Question 21

what other pathology may occur

Answer 21

rare or low numbers of inflammatory cells may be present

Question 22

what is the pathology shown here

Answer 22

hypertrophied synovial villi

low numbers of lymphocytes and plasma cells

Question 23

what lesions can be seen

Answer 23

Question 24

what lesions are shown here

Answer 24

Question 25

what lesions are seen

Answer 25

Question 26

what is the pathogenesis in the development of osteoarthritic changes in joints

Answer 26

1. primarily degenerative in nature, accompanying inflammatory changes are secondary 2. disruption of balance between degradation and repair cartilage matrix in favour of matrix breakdown leads to loss of proteoglycans and damage to collagen fibrils 3. leads to loss of viscoelastic properties of articular cartilage, and further loss of cartilage with biomechanical trauma

Question 27

what occurs in the balance between synthesis and degradation of cartilage matrix

Answer 27

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

Question 28

what degrading enzymes lead to the early loss of matrix components

Answer 28

1. metalloproteinases 2. serine proteinases 3. cysteine proteinases 4. aggrecanse

Question 29

why do degradtive enzymes have an effect

Answer 29

natural inhibitors of these enzymes are normally present in articular cartilage but are deficient in degenerative joint disease

Question 30

what else is involved in the pathogenesis

Answer 30

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

Question 31

what are inflammatory changes secondary to

Answer 31

stimulation of IL-1 and TNF-alpha by synoviocytes following release of degraded collagen and proteoglycan fragments from degenerate cartilage

Question 32

what is bacterial arthritis

Answer 32

following bacteremia common in horses and food animals sequel to neonatal bacteremia

Question 33

what does bacterial arthritis cause

Answer 33

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)

Question 34

how is bacterial arthritis caused

Answer 34

implantation, penetrating wound --\> affects one joint, mixed bacterial population

Question 35

what pathology is seen

Answer 35

fibrinous arthritis in the carpus abundant yellow fibrin fills the recesses of the joint articular cartilage is smooth and unaffected

Question 36

what is seen here

Answer 36

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)

Question 37

what are common aetiologies of bacterial arthritis

Answer 37

1. coliform arthritis (E. coli) --\> neonatal septicemia in farm animals 2. staphylococcal arthritis (S. aureus) --\> common in farm animals and monoarticular arthritis in dogs 3. erysipelothrix rhusiopathiae --\> causes porcine erysipelas which can result in articular lesions --\> erysipelas infection in sheep usually follows cuts or abrasions 4. chlamydial arthritis (C. pecorum) --\> cause of arthritis in calves and lambs 5. mycoplasmal arthritis (M. hypopneumoniae and M. hyosynoviae in pigs, M. bovis in cattle, mycoplasma in sheep) 6. borreliosis (lyme disease) --\> dogs, multiple joints affected

Question 38

what is viral arthritis

Answer 38

caprine arthritis-encephalitis virus

Question 39

what is fungal arthritis

Answer 39

rare with systemic fungal infections (blastomyces, histoplasma, cryptoccocys)

Question 40

what is immune mediated polyarthritis

Answer 40

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

Question 41

what is seen here

Answer 41

immune mediated polyarthritis ex. rheumatoid arthritis