Pathology of Joints Flashcards
What are joints, or articulations?
place where two or more bones are united by fibrous, elastic, or cartilaginous tissues or a combination of these tissues
What are the 3 types of joints? Give examples of each.
- FIBROUS JOINTS: synarthroses; bones united by fibrous tissue (between cranial bones, between teeth and alveolar bones
- CARTILAGINOUS JOINTS: amphiarthroses; bones united by hyaline cartilage (costochondral joints) or fibrocartilage (pelvic and mandibular symphyses, intervertebral joints)
- SYNOVIAL JOINTS: true joints, diarthroses; bone ends covered by hyaline articular cartilage and surrounded by articular capsule filled with synovial fluid
Synovial joint:
What type of joint is most likely to have lesions in domestic animals?
diarthrodial joints (synovial joints)
What are the 3 joint reactions to injury?
- FIBRILLATION (fraying) - articular cartilage erosion causing collage exposure and proteoglycan loss
- eburnation - articular cartilage ulceration
- joint mice formation
What happens to the subchondral bone underneath eburnated cartilage?
- bone will rub bone and cause pain (nerve endings in bone and not cartilage)
- becomes increasingly dense (osteosclerosis) to support trauma
- inflammation
What causes osteophyte formation? What is it? Where is this most common?
chronic joint injury - nodular proliferation of bone covered by cartilage
chondro-osseous margin where increased mobility occurs
What is villous hypertrophy/hyperplasia?
thickening of the usually thin and translucent synovial membrane due to chronic joint injury (finger-like projections)
(loss of cartilage from femur head)
What is pannus formation?
fibrovascular (granulation) and histiocytic tissue that develops within the synovial membrane at its junction with the periosteum and cartilage margins (transitional zone) and can spread over the articular surfaces as a velvety membrane
What does the infiltration of inflammatory cells in the pannus formation cause?
(+ collagenases from synovial fibroblasts) can further damage the articular cartilage and lead to ankylosis, or fixation, of the joint
What does “end-stage joint” mean? What do affected joints exhibit?
- generic term to describe a joint with severe chronic injury
- variable degrees of damage to the articular cartilage, deformation, osteophyte and pannus formation, capsular fibrosis, synovial villous hypertrophy/hyperplasia, and occasional ankylosis
What is osteochondrosis (dyschondroplasia)? What is a common sequel?
developmental joint disease characterized by abnormal growth and maturation of the articular cartilage
- severe degenerative joint disease
What is osteochondrosis (dyschondroplasia) the most common cause of? What is thought to affect pathogenesis?
- lameness in domestic animals, especially swine, horses, poultry, and large breed dogs (rapidly growing pigs can reach 100% incidence)
- ischemic damage to the growing cartilage due to an unknown and underlying cause
What is osteochondrosis/osteochondritis dissecans (OCD)? What does this cause in the synoial joint?
form of osteochondrosis characterized by the separation of a piece (flap) of articular cartilage from the subchondral bone
formation of joint mice that are able to use the nutrient-filled synovial fluid to survive and grow
When is osteochondrosis/osteochondritis dissecans (OCD) most common? What syndrome is commonly caused when it affects the elbow?
young, fast-growing males of large/giant breeds, commonly affecting shoulder and elbow joints
elbow dysplasia syndrome - ununited anconeal process and fragmented medial coronoid process of the ulna
How does osteochondrosis/osteochondritis dissecans (OCD) affect horses?
- common cause of lameness in foals and younger horses
- lesions can be widespread, but the stifle, hock, and fetlock joints are most commonly affected sites
OCD, dog humerus:
OCD, horse distal femur:
focal cartilage ulceration on trochlea with surrounding discoloration
OCD, pig humerus:
- thickness is not uniform
- ischemia of subcondral bone that is beginning the flap formation process
OCD histology, horse humerus:
OCD lesion, horse distal femur:
flap broke off into synovial joint
OCD lesion comparison:
abnormal growth of articular cartilage and subchondral bone resulting in deformation of the trochlear groove and ridges
OCD, pig:
Osteochondrosis, pig:
- nodules represent regenerative attempts at repair
- villous hypertrophy
OCD, pig:
- flap separated from bone
- villous hypertrophy
In what animals is hip dysplasia a common issue? What is it characterized by?
large breed dogs
lack of conformity between the femoral head and the acetabulum, leading to subluxation and degenerative joint disease
What is thought to play a significant role in the development of hip dysplasia? What is an early finding?
environmental factors, like nutrition and rapid growth
- polygenic mode of inheritance has been postulated
joint laxity (instability)
Hip dysplasia, femur:
cartilage erosion leads to flattening of femur head not allowing for conformity into the joint
Hip dysplasia, femur head lesions:
- eburnation
- fibrillation
- thickened connective tissue, capsule, and synovial membrane
What are the 2 types of intervertebral disk disease?
Hansen’s Type I: nucleus pulposus extrudes into vertebral canal through connective tissue (most severe)
- most common in chondrodystrophic breeds at younger ages
Hansen’s Type II: nucelus pulposus protrudes into the vertebral canal without rupturing the connective tissue (whole disk pushes into canal)
- age-related, more subtle with time
What is IVDD the most common cause of in dogs?
posterior paresis
IVDD, dog:
fibrocartilage intact —> Hansen’s Type II, age-related
What is spondylosis deformans (ankylosing spondylosis/itis)? What is the initial lesion like?
common degenerative disease of the vertebral column characterized by the formation of osteophytes at the ventral and lateral margins of vertebral bodies adjacent to vertebral spaces
degenerative changes in the ventral annulus fibrosus
In what animals is spondylosis most common?
- old bulls
- pigs (sows and boars)
- dogs
(thoracolumbar region!)
How does the finding of spondylosis lesions compare in bulls and dogs?
BULLS: seen in almost every bull past middle age and is especially common in those used for artificial insemination (large, at work everyday)
DOGS: usually an incidental (subclinical) finding but may cause mild to severe clinical signs like posterior weakness, ataxia, or paralysis
Spondylosis deformans:
- compresses spinal nerve exits
- compensatory osteosclerosis due to increased mobility and stress on bone
Ankylosing spondylosis:
- osteophyte formation and fixation to the right
- 2 bodies fused
Lumbar segment of vertebral column leading to lordosis:
- yellow in marrow = osteosclerosis
- periosteum induces the prodution of new bone for compensation
- lordosis is accentuated by live animal weight pulling it down
What is the difference between primary and secondary degenerative joint disease (osteoarthritis/osteoarthrosis)?
PRIMARY: no apparent predisposing cause, generally observed in older animals
SECONDARY: associated with an underlying abnormality in the joint or its supporting structures which leads to premature degeneration of the articular cartilage (hip dysplasia, trauma, inflammation)
What is ringbone? In what animals is it most common?
degenerative disease in horses affecting the inter-phalangeal (coffin) joints characterized by bone compensating for chronic traumatic injury by growing around the tendons of the flexors and extensors
horses used in rodeo events, barrel racing, or polo where they ensure abrupt stops, turns, and twists
What are 5 common routes of infection in inflammatory joint disease?
- iatrogenic
- septic (hematogenous)
- local trauma (osteomyelitis)
- exogenous trauma
- inflammation of surrounding tissues leads to neutrophil tunneling into the joint
In what animals is inflammatory joint disease most common?
farm animals, especially the young where it is a common consequence of neonatal bacteremia
When does non-infectious arthritis commonly occur?
in dogs and cats that have an immune-mediated etiology (like rheumatoid arthritis)
What are 10 common bacteria isolated from septic arthritis?
- Trueperella (Arcanobacterium) pyogenes - cattle, swine
- Erysipelothrix rhusiopathiaw - swine, sheep, birds (diamond skin disease!)
- E. coli - calves, piglets
- Strep suis - pigs 2-10 weeks
- Haemophilus suis/parasuis - pigs 5-12 weeks
- Mycoplasma hyorrhinis - pogs 3-10 weeks
- Mycoplasma hyosynoviae - pigs > 10 weeks
- Histophilus somni - cattle
- Histophilus bovis - cattle
- Borrelia burgdorferi - Lyme disease in humans and dogs
What is caprine arthritis-encephalitis (CAE)?
slowly progressive disease of goats caused by a retrovirus that produces respiratory and neurological syndomes, alond with joint lesions characterized by lymphocytis hyperplastic synovitis with the formation of carpal hygromas
What are carpal hygromas? What does a high prevalence of hygromas and lameness in a goat herd point to?
chronic lesions that appear as flattened cystic fluid-filled subcutaneous distensions over the cranial carpus, usually with no communication with the carpal joint or tendon sheath
viral caprine arthritis-encephalitis (CAE)
What is non-infectious arthritis? What is it usually caused by?
arthritis with an immune-mediated etiology (rheumatoid-like) where the inflammation is in response to persistence of antigens in the synovial membrane of affected joints
- previous infection
- deposition of immune complexes in in the synovium from inflammatory lesions elsewhere
In what animals is non-infectious arthritis most common? What are the 2 types described?
dogs and cats with polyarthritis
- erosive
- non-erosive
Where do malignant neoplasms of joints arise from? What are the 2 types?
synovial membrane (uncommon in dogs and very rare in other species)
- SYNOVIAL CELL SARCOMA: malignant tumors arising from synovial fibrocytes
- HISTIOCYTIC SARCOMA: malignant tumors arising from cells of histiocytic phenotype, like dendritic (Langerhans) cells, in the synovium
