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In addition to provide mechanical support and protecting key organs from traumatic injury bone plays an important role

In addition to provide mechanical support and protecting key organs from traumatic injury bone plays an important role in Ca homeostasis.


“Bones are

Bones are dynamic organs undergoing constant remodeling throughout life”


Are Diseases of bone diganosed a lot?

Diseases of bone are often under-diagnosed


Bone is a specialized

Bone is a specialized connective tissue consisting of cells embedded within a gel-like substance that becomes mineralized


Bone has the property of

Bone has the property of marked rigidity and strength whilst retaining some degree of elasticity


To accommodate changes related to mechanical stresses and demands on calcium homeostasis bones are

To accommodate changes related to mechanical stresses and demands on calcium homeostasis bones are in a dynamic state of growth and resorption throughout life.


Like other types of connective tissue bone is composed of

Like other types of connective tissue bone is composed of cells and an organic extracellular matrix containing primarily glycoproteins and collagen fibersthis matrix is known as osteoid. Osteoid rapidly undergoes mineralization (by deposition of inorganic salts, mainly calcium hydroapatite (CHAP) crystals, to form bone.


The bone matrix also contains a variety of

The bone matrix also contains a variety of growth factors which probably play an important role in bone development, modeling and remodeling.


Cellular elements of bone

• Osteoblasts- produce osteoid, immature cells of bone

• Osteocytes- mature cells of bone
• Lining cells (inactive osteoblasts)

• Osteoclasts- multinucleated cells that reabsorb bone- maintain Ca + metabolism


pinkish- osteoid

large mulitnucleated cells- osteoclasts that liberate ca into the blood


There are two types of bone based on the degree of maturity...

  1. Woven bone: Immature bone present during fetal development and in the early stages of bone repair. Collagen fibers in woven bone are randomly arranged adopting a crisscross (woven) pattern microscopically.

  2. Lamellar bone: Mature bone. Collagen fibers are arranged in a parallel pattern.

according to the stage of maturation bone(cortical or canellous) could be either woven or lamelluar


During fetal life bone formation occurs in 2 ways, both of which involve replacement of connective tissue by bone:

  1. Intramembranous ossification – Occurs within “membranes” of condensed primitive mesenchymal tissue  flat bones of the skull ONLY

  2. Endochondral ossification – Occurs in the majority of bones of the skeleton (limbs, vertebral column, pelvis, base of the skull). Bone develops from a cartilaginous model (hyaline cartilage) that is subsequently replaced by osseous tissue present in the so called ossification centers.


epiphyseal plates

Endochondral ossification occurs in the ossification centers of immature bones and in the growth plates (epiphyseal plates) of developing bones.



Once the growth plates are closed (mature animal),

Once the growth plates are closed (mature animal), no further longitudinal growth (resulting in increase length) can occur.


growth plate

Bottom- begining of mystephosis- spoongy bone

Top- resistin cartilage- chondro  cysts are isolated

Proliferative(p) layer



Chondrodysplasia (Chondrodysplasia fetalis or disproportionate dwarfism)


Breed-associated, usually hereditary conditions that occur in dogs, cattle and sheep. Membranous appositional growth is normal but interstitial growth of cartilage is abnormal resulting in premature close of growth plates and decrease length of long bones (affects bones that form by endochondral ossification).

Most common in beef breeds (Angus, Hereford). In Dexter cattle, homozygote animals for the Dexter phenotype (Dexter “bulldog” dwarfism) are severely deformed and are usually aborted before 7 months of gestation (lethal form of chondrodysplasia).


“Dexter bulldog

“Dexter bulldog” – Congenital lethal Chondrodysplasia

Inherited condition of Dexter cattle.
Affected calves are often aborted and exhibit disproportionate dwarfism,
short vertebral column, marked micromelia (shortening of the limbs),
large head with short muzzle, protruding

tongue and large abdominal hernia


Chondrodystrophic dog breeds exhibit

Chondrodystrophic dog breeds exhibit localized chondrodysplasias involving specific bones.


Daschumonds- Micromelic achondroplasia(very short limbs)

Other brachicephalic chondrodystrophic dog breeds are Bulldogs and Boxers

Basset hound


Cervico-vertebral stenotic myelopathy (Wobbler‟s syndrome)

- This a localized skeletal dysplasia most common in horses and large breed dog

- It can also be classified as a degenerative joint disease which affects the axial skeleton.

- The syndrome results in dynamic or static compression of the cervical spinal cord (SC) by abnormal cervical vertebrae.

-In the dynamic form sc compression occurs when the neck is flexed; in the static form sc compression occurs no matter what position the neck is in.

Wobbler's in horses and large breed dogs


Cervical vertebral stenotic myelopathy

in Doberman

"ski-slope lesions"


Wobbler Syndrome, horse

static- severe compression of the cervical canal



Osteopetrosis (petros: rock)

Inherited disease caused by osteoclast failure to reabsorb the primary spongiosa. This failure results in an increased bone density and lack of medullary (bone marrow) spaces.


Metaphyseal Dysplasia

Osteopetrosis is an heritable condition also known as “Metaphyseal Dysplasia” results in diffuse osteosclerosis (↑ bone density).

Since there is no space for the hematopoietic tissues of the bone marrow to grow, affected animals often present aplastic anemia. Affected bones have an increased susceptibility to fracture. Reported mainly in dogs, sheep, cattle and horses.


- Aplastic anemia





Congential  Cortical hyperostosis of pigs

Autosomal recessive inherited condition in pigs.

• Limbs (primarily the forelimbs) appear swollen due to excessive deposition of radiating trabeculae on the periostal surface, and blockage of the local lymphatic circulation.

Most affected pigs are born dead or die within hours- lame animals that can not stand

This abnormality has been compared to Caffey‟s disease (infantile cortical hyperostosis) observed in children and monkeys.


Localized malformations

Localized malformations

• Limbs (appendicular skeleton)
• Amelia: Absence of a limb(s|)
• Hemimelia: Absence of the distal half of a limb
• Polymelia: Supernumerary limbs
• Phocomelia: Abscense of the proximal portion(s) of a limb(s)

• Micromelia: Abnormally small or short limb(s)
• Syndactylia: Fusion of the digits
• Polydactylia: Supernumerary digits
• Others...



Absence of a limb(s|)



Absence of the distal half of a limb



Supernumerary limbs



Abscense of the proximal portion(s) of a limb(s)



Abnormally small or short limb(s)



Fusion of the digits



Supernumerary digits



Ventral deviation of the vertebral column



Dorsal deviation of the vertebral column



Lateral deviation of the vertebral column



Dorso-lateral deviation of the vertebral column


Dorsal deviation of the spinal column- kyphosis


Angular limb deformities

Angular limb deformities – Relatively common in young animals and specially important in horses. In many cases (not all) the origin of the deformity can be traced to an asymmetric lesion in an active growth plate. Characterized by twisting of the bone: lateral (outward) deviation (valgus deformity) or medial (inward deviation (varus deformity) of one or more limbs distal to the affected growth plate or joint. Present at birth or may develop later in life. Causes may include:

- Malposition in utero
- Joint laxity
- Hypothyroidism (congenital goiter)
- Trauma (ischemia or reduced blood supply) - Malnutrition
- Impaired endochondral ossification


Carpal Valgus, foal.


Metabolic Bone Diseases

• Also referred as osteodystrophies

Result from disturbed bone growth, modeling or remodeling due to either nutritional or hormonal imbalance.

MBD is characterized by failure of production of bone matrix, its mineralization or its maintenance.


Metabolic Bone Diseases Etiology

Nutritional: Vitamins C, D, Ca, P, Protein

Hormonal: Parathyroid (PTH), Thyroid (calcitonin),

gonads (estrogens), adrenal problems (corticosteroids).

Disuse: Physical inactivity

Toxic: Lead and fluoride poisoning, hypervitaminosis A etc.


Can  metabolic bone diseases have more than one etiology?

In a particular individual metabolic bone diseases can have more than one etiology. In addition, different forms of metabolic bone disease (osteodystrophies) can coexist in the same individual.


In domestic animals metabolic bone disease caused by nutritional deficiency

In domestic animals metabolic bone disease caused by nutritional deficiency is often caused by deficiency of more than one nutrient.



Characterized by osteopenia (↓ in the amount of bone tissue). “ there is a ↓ amount of bone but the bone that is present is normal. Grossly there is a reduction in the thickness of the cortical bone and a ↓ number of trabeculae in the cancellous bone.


Osteoporosis Etiology

1. Nutritional
Starvation(MOST COMMON), Cu deficiency, Vitamin C deficiency.

2. Aging

In humans peak bone mass occurs around the age of 30; there after resorption outpaces bone formation.

3. Disuse


Goat, osteoporosis/ osteopenia – Cornell Serous atrophy of bone marrow -Starvation


From McGavin: Sheep Osteopenia/ osteoporosis


Heifer – starvation Serous atrophy of BM Fat, Cornell Files

osteoporosis- MIGHT BE, but it's hard to diagnosis



Metabolic bone disease of a complex etiology affecting young growing animals.

The basic pathogenesis involves defective calcification of osteoid and defective endochondral ossification.

Etiology is multifactorial but typically involves vitamin D or phosphorous deficiency.

Exposure to sunlight (solar ultraviolet radiation is also important).


Gross Lesions in Rickets

o Irregular thickening of growth plates with tongues of uncalcified

cartilage extending into the metaphysis

o Widening of growth plates  enlarged ends of long bones; enlargement of costochondral junctions (“rachitic rosary”); weight-bearing long bones may become bowed

o Hemorrhages beneath the articular cartilage or in growth plates o Pathological fractures may occur
o At necropsy ribs bend rather than snap


Rickets. Dog from India


Osteodystrophic (growth- arrest) lines –Rickets-Foal


Chicken: Rachitic rosary



A disease of grown (adult) animals (closed growth plates).

Similar pathogenesis to rickets: failure in the mineralization of

osteoid primarily due to vitamin D or P deficiency.

Unmineralized osteoid is resistant to osteoclastic resorption and accumulates in the bone.

Affected animals may exhibit bone pain (shifting lameness), pathologic fractures and deformities such as kyphosis, lordosis and scoliosis.

Collapse of articular surfaces may occur.


Fibrous Osteodystrophy

(osteodystrophia fibrosa; osteitis fibrosa cystica)

Relatively common metabolic bone disease characterized by extensive bone resorption and replacement by fibrous connective tissue and poorly mineralized immature bone.

• The disease is the result of persistent elevations of plasma PTH levels (hyperparathyroidism).

• More common in horses, pigs, dogs and cats. Also seen in reptiles and New World Monkeys.


Fibrous Osteodystrophy Mechanism:

Primary Hyperparathyroidism-

Fibrous Osteodystrophy (Basic mechanism: ↓Ca; ↑P= ↑PTH)

Due to primary or secondary hyperparathyroidism.

Primary Hyperparathyroidism:

- Usually associated with functional parathyroid adenomas in dogs.

- Affected animals exhibit marked hypercalcemia and hypophosphatemia.

- Lesions may include FO; Thyroid C-cell hyperplasia; hypercalcemic nephropathy (nephrocalcinosis) and metastatic mineralization in soft tissues.


Secondary Hyperparathyroidism(MORE COMMON)

1. Nutritional: Dietary deficiency of Ca; excess dietary P, or deficiency of Vitamin D. In most cases nutritional secondary hyperparathyroidism is the result of ↓Ca or ↑ P in the diet and, with the exception of horses, affects young growing animals.

2. Renal: Complex etiology but P retention due to loss of glomerular function and the inadequate synthesis of 1, 25 Dihydroxyvitamin D (1,25, dihydroxy cholecalciferol, calcitriol) by the kidney play a mayor role.

Renal osteodystrophy occurs more commonly in the dog. Bones, especially those of the head become swollen and are firm rather than hard, maxilla and mandible are usually affected. The mandibles may become quite pliable (“rubber jaw”). Teeth are often mobile and malpositioned within the swollen gums and alveolar bone.


Fibrous osteodystrophy, Horse. Loss of bone and replacement by fibrous connective tissue.


"Bran disease or Big head"


“Rubber jaw” – Renal Osteodystrophy, dog Cornell files.



Fibrous osteodystrophy

teeth become burried


Shih-Tzu, Renal osteodystrophy, Cornell files.


fibrous osteodystrophy


teeth are embedded in the proliferative tissue


Fibrous Osteodystrophy

-metabolic bone disease characterized by extensive bone resorption and replacement by fibrous connective tissue and poorly mineralized immature bone.

-the result of persistent elevations of plasma PTH levels (hyperparathyroidism).

-Primary( rare, but can see in dogs with tumors) or secondary( more common- nutritional)

-Secondary (most common) can be:

• Nutritional (low Ca or high P diets) or Renal


Toxic Osteodystrophies

Lead poisoning: Lead interferes with osteoclastic activity. Subtle bone lesions leads to Increase bone density (osteosclerosis) in the metaphysis leads to “lead line”- near the growth plate in a young animal or the episeal plate in a mature animal- LEAD INHIBITS OSTEOCLAST REABSORPTION

Fluoride toxicosis: Occurs in herbivores mainly cattle and sheep. Affects the normal metabolism of bone and teeth primarily in growing animals. Ameloblasts(produce enamel) and odontoblasts(produce dentin) are markedly sensitive to excess fluoride and the result are soft dark-brown discolored teeth that wear down easily (defective enamel and dentine - odontodystrophy). Bones exhibit periosteal hyperostosis.- fluoride may be present in underground water

Hypervitaminosis A: The most well know syndrome is observed in cats that consume high quantities of bovine livers (high vitamin A content) for a long period of time   leads to deforming cervical  ankylosing(fixation) spondylosis. The disease is more common in Australia and Uruguay. Affected cats develop osteophyte formation around the joints of the cervical vertebrae, shoulder and elbow. (also known as cervical ankylosing spondylosis or disseminating ankylosing osteoarthropathy).


Bone Reaction to Injury

Necrosis: Osteonecrosis or Osteosis. In animals bone ischemia is usually associated with trauma but may also occur in inflammatory and neoplastic bone diseases. Necrotic bone appears paler.

Microscopically: Cell death with loss of osteocytes from their lacunae.- empty lacunae


Outcome of osteonecrosis

-Influenced by the size and extent of necrosis and by the extend and strength of collateral circulation and local repair mechanisms.

-Complete resorption and replacement of necrotic bone may occur

-Formation of a “sequestrum”  A piece of necrotic bone isolated from the remaining viable bone.

-Attempts to wall off a sequestrum will result in the formation of a layer of granulation tissue and reactive bone known as an “involucrum”


Foal, focal osteomyelitis with sequestrum(toward the bottom of the picture). Cornell Files

in a young animal


sequestrum will result in the formation of a layer of granulation tissue and reactive bone know as an "involucrum"



 Bone Fractures

Traumatic: Normal bone broken by excessive force

Pathologic: Abnormal bone broken by minimal trauma or normal weight bearing

Complete or Incomplete

Closed (simple) or Open (compound- poor prognosis because of the exposure to the outside world)

Comminuted- fracture that results in mulitple bone fragments

Avulsed: Caused by the pull of a ligament/muscle tendon at its insertion into bone.

Microfracture/ infraction: fracturing of trabeculae without external deformation of cortical bone--- more on the microscopic level


Cornell,  Pathologic fracture, Osteosarcoma, dog




Fracture Repair


Healed humeral fracture, feedlot steer, UCVM, OI


Complications associated with bone fractures

-Bone necrosis and formation of a sequestrum

-Nonunion fracture pseudoarthrosis (false joint) formation

-Osteomyelitis (compound fractures)

-Cachexia( wild animals)


Pig – vertebral abscess resulted in fracture of the vertebral body and focal compression of the spinal cord, common sequel of tail biting. AVC

can cause intendtion of the spinal cord


rib fractures are difficult


Aseptic inflammation

rauma may cause osteoperiostitis with formation of exostosis (osteophytes).



Local or systemic (hematogenous route)



Most common in young farm animals as the result of bacteremia or septicemia



Omphalophlebitis is a common source of osteomyelitis in neonates


In piglets Osteomyelitis often localizes in

 In piglets the infection often localizes in vertebral bodies


Osteomyelitis also tends to localize in

Infection also tends to localize in metaphyses of long bones due to the microanatomy of vessels.


Blood vessel from the bone marrow come close to the growth plate and turn very softly


bacteria can colonize easier


Physitis has extended to the periosteum and metacarpal phalangeal joint, foal


osteomylitis- change in the color of the bone- have a rim of inflammation/congestion; in the area of the growth plate


Embolic osteomyelitis, foal. Note Area of bone necrosis (arrow).


lesions cloase  to epiphysisal growth plate

sequestrium- necrosis and inflammation

bacteria that can cause this: E. coli,  salmonella(espesically in foals),


Bovine Actinomycosis, “lumpy jaw”, UCVM

pyogranolomatous osteomylitis

Etiological agent- actinomyces bovis

engorgment of the mandible

Involvment of the mandbile and maybe maxilla




Chronic pyogranulomatous osteomyelitis – Actinomycosis


lesions in the mouth or a bad tooth- can be portal of entry


Pyogranulomatous Osteomyelitis, Actinomycosis


sulfur granules- characterisitized by large bacterial colonies surrounded by neutrophils and on outside- macrophages, lymphocytes


Splendore Hoeppli- eosinophilic filaments that surround the bacteria- represents the antigens/antibody complexes


Gram positive bacteria, Actinomyces bovis, UCVM, OI





“Lumpy Jaw” (Actinomycosis) – cow.
Actinomyces bovis. Note osteolysis of the macerated and bleached bone specimen- bone remodeling


Chronic pyogranulomatous Osteomyelitis

Nocardia spp. was identified by culture and PCR


Hypertrophic pulmonary osteoarthropathy or osteopathy.


• Sporadically reported in humans (“Marie’s Disease”) and domestic animals, specially dogs.

• Usually observed in individuals with an intra-thoracic space- occupying mass (tumor, abscess).

Characterized by painful swelling of limbs caused by periosteal bone proliferation (hyperostosis) in long bones.

Bone changes can regress if the space-occupying lesion in the thoracic cavity is removed.


Hypertrophic pulmonary osteoarthropathy or osteopathy is also occasionally observed.

In young dogs with rhabdomyosarcomas(skeletal muscle malignant tumors) of the urinary bladder and mares with ovarian tumors.


bone proliferation along the periosteium


Canine craniomandibular osteopathy (“Lion Jaw”)


Proliferative disorder confined to the bones of the skull, especially the mandibles, occipital and temporal bones

• Most Common in West Highland White Terriers were a genetic etiology is suspected.

• Usually recognized at 4-7 months of age

• Affected dogs may exhibit discomfort when chewing or inability to open the mouth to eat.


Canine craniomandibular osteopathy (“Lion Jaw”)


West Highland White Terrier


Bone Neoplasia

Primary tumors are more common than secondary tumors(metistatic)

Primarily observed in dogs and to a lesser extent cats

Tumors of bone and cartilage cell-lines are the most common

In dogs most tumors of bone are malignant- osteosarcoma and chondrosarcoma

In horses, cattle and other domestic animals benign tumors of bone are more common than malignant ones


Primary Bone Neoplasms

Osteoma- benign tumor of bone
Ossifying fibroma- can be seen in young horses- in the cranial portion of the manidle




Multilobular tumor of bone- tumor in dogs; located in the skull- locally aggressive; grows slowly but because of location - it can supress the brain and cause death


Osteoma, maxilla, Sheep-McGavin


we don't see a lot of primary bone tumors in LA



Most common primary bone tumor in dogs and cats

Highest incidence in Large breeds like St. Bernard, Great Dane, Irish Setter, Boxer, Doberman, Rottweiler and Labrador Retrievers

Mean age of affected dogs is 7.5 years but dogs less than 2 years old can be affected

Most common in male dogs


In the dog osteosarcoma has
a relatively specific site predilection:

In the dog osteosarcoma has
a relatively specific site predilection:
“Close to the knee and away from the elbow”



Osteosarcoma, 11 y- Female Rottweiller,


poor prognosis


Osteosarcoma, 2 year-old Poodle, Atlantic Veterinary College


stifle joint



Accounts for approximately 10% of primary bone tumors in the dog

Rare in other domestic animals

In all species it involves flat bones (ribs, nasal turbinates and pelvis) more often than long bones


Chondrosarcoma, skull, dog -McGavin


Example of chondrosarcoma in a long bone- humerus of a mastiff


Chondrosarcoma, rib, cat, McGavin


Chondrosarcoma, humerus


Chondrosarcoma, humerus


Articulations or joints are formed when

Articulations or joints are formed when two or more bones are united by fibrous, elastic or cartilaginous tissues or by a combination of these tissues


Types of Joints

1. Fibrous joints (synarthroses): Bones are united by fibrous tissue. a. E.g., sutures: cranial bones

b. syndesmosis: tibial-fibular joint

c. gomphoses: Teeth and alveolar bone

2. Cartilaginous joints (Amphiarthroses): Bones are united by hyaline cartilage (e.g., costochondral joints) or fibrocartilage (pelvic and mandibular symphyses, intervertebral joints).

3. Synovial Joints (True joints or Diarthroses): Unite two bone ends covered by hyaline articular cartilage and an articular capsule surrounds a cavity filled with synovial fluid.


Joint reaction to injury

Most common joint lesions in domestic animals involve synovial (diarthrodial) joints

• Injury to articular cartilage results in erosion/fibrillation(fraying- loss of cartilage and extracellular matrix), eburnation( all of the articular cartilage is gone!- exposure of the subchronal bone and has a shiny apperance) or “Joint mice” formation


On left- normal

on right- abnormal

left center- erosion of the bone

right/right center- complete loss of articular cartilage


Osteophyte formation(lumps) may be a sequel of chronic joint injury- this will help with formation of new bone(bone spurs)


articular cartilage looks granular, it's discolored. There is erosion here



Villous hypertrophy/ hyperplasia of the synovial membrane is other manifestation of chronic joint injury


femoral head- loss of articular cartilage; exposure of subchondral bone- characterized by erosion of bone


Pannus formation

another possible sequel to chronic joint injury



Pannus is a 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.

Inflammatory cells within the pannus along with collagenases from synovial fibroblasts may further damage the articular cartilage and lead to ankylosis (fixation) of the joint.


Pannus formation


End-stage Joint

Generic term to describe a joint with severe chronic injury.

Affected joints exhibit variable degrees of damage to the articular cartilage, deformation, osteophyte and pannus formation, capsular fibrosis, synovial villous hypertrophy/ hyperplasia and occasional ankylosis (fixation, immobility).


Osteochondrosis (Dyschondroplasia)

Developmental Joint Diseases:


Characterized by abnormal growth and maturation of the articular cartilage

Severe degenerative joint disease is a common sequel
It is the most common cause of lameness in domestic animals, especially swine, horses, poultry and large breed dogs

Pathogenesis is multifactorial but poorly understood

Whatever the underlying causes ischemic damage to the growing cartilage seems to play a significant role

In rapidly growing pigs the incidence may reach close to 100%


Osteochondritis Dissecans (OCD)

Osteochondritis Dissecans (OCD) specific form of osteochondrosis

 Specific form of osteochondrosis characterized by the separation of a piece (flap) of articular cartilage from the subchondral bone.

In dogs lesions are more common in young fast-growing males of large and giant breeds and affect primarily the shoulder and elbow joints. Lesions in the elbow joint form part of the “elbow dysplasia syndrome” which also includes ununited anconeal process and fragmented (or ununited) medial coronoid process of the ulna; important orthopedic conditions in young dogs.


OCD is an important disease in

OCD is an important disease of horses and a common cause of lameness in young animals.


In horses OCD lesions can be___


common affected sites?

In horses OCD lesions can be widespread but the stifle, hock and fetlock joints are commonly affected sites.


OCD lesions in dogs.  SHOULDER COMMONLY AFFECTEDHumeral head


OCD lesions in dogs. Humeral head

deformaty in the bone


Stifle joint in a horse

areas of ulceration


humerus of a pig OCD or osteochondritis dissencants



OCD lesion, distal femur, lateral ridge, horse


erosion  and ulceration with exposure of the underlying subchondrol bone


OCD lesion, distal femur, lateral ridge, horse, UCVM – 2009
Note abnormal growth of the articular cartilage and subchondral bone resulting in deformation of the trocheal groove and ridges, OI.


Osteochondrosis, Pig, femoral head




normal femoral head, pig


Osteochondrosis dissenticans, pigs, UCVM, OI


Hip Dysplasia

  Very important orthopedic disease in large breed dogs(German Shepards espesically) – occasionally seen in other species

  Characterized by a lack of conformity between the femoral head and the acetabulum leads to subluxation which leads to DJD.

  Polygenic mode of inheritance has been postulated in dogs but environmental factors as nutrition and rapid growth plays a significant role

 Joint laxity (instability) is an early finding


Femur (femoral head) –Dog with hip Dysplasia


subchondral bone is gone


DJD –Hip Joint, Aged German Shepherd


erosion of the articular cartilage


Intervertebral Disk Disease

 Occurs in all dog breeds as part of the aging process

 There are differences between IDD in chondrodystrophic(Dashunds etc, these are pre-diposed) and non- chondrodystrophic breeds regarding the age of onset and the nature of the degenerative changes

 IDD is one of the most common causes of paresis in the dog


Hansen’s type I (B) - DASHSUNDS- Disk Extrusion

type II (A)- MORE COMMON IN NON- CHRONDODYSTROPIC DISEASES- Protrusion- associated with aging


IDD - Dog-

Hanesne's  Type II- as seen in older dogs



Spondylosis (spondylosis deformans, ankylosing spondylosis (itis)

“ Common degenerative disease of the vertebral column characterized by the formation of osteophytes(bone spurs) at the ventral and lateral margins of vertebral bodies adjacent to vertebral spaces” –JKP- G Maxie, Ed-2007

The initial lesion appears to be degenerative changes in the ventral annulus fibrosus- this results in fixation of the joints


Spondylosis is most common

Spondylosis is most common in old bulls, pigs (sows and boars) and dogs


assoicated with increased age



Lesions are seen in almost every bull past the middle age and is especially common in those used for artificial insemination.

Usually an incidental finding but may cause mild to severe clinical signs (posterior weakness, ataxia or even paralysis).


Spondylosis deformans, 20 year-old donkey, TAMU


Ankylosing spondylosis – aged bull, Cornell Show and Tell, Dr. King Macerated and bleached bone specimen.
Osteophytes (“bone spurs”).


31 year-old gelding In thin body condition
(395 kg). Loosing weight.

In addition to swayback this horse had severe degenerative joint disease. Poor tail tone and mild proprioceptive deficits in the hind limbs were noticed on examination

Lumbar segment of vertebral colon, Intervertebral disk disease (IDD) Leading to sub-luxation of L3-L4; formation of oseteophytes



Close up of the lesions in the medial condyle of the right humerus


lordosis(ventral deviation of the spinal column)


Degenerative Joint Disease –Synovial Joints (osteoarthritis/ osteoarthrosis)

Primary DJD: No apparent predisposing cause. Generally observed in older animals (age-related DJD).

Secondary DJD: Associated with an underlying abnormality in the joint or its supporting structures which leads to premature degeneration of the articular cartilage (e.g.: hip dysplasia in dogs, trauma, inflammation)- atheletes



Degenerative disease in horses affecting the inter-phalangeal joints (Secondary  DJD)

chronic trauma to the joints

common in horses used in rodeo or polo events


Common in horses used in rodeo events or Polo  chronic trauma. The result of abrupt stops, turns and twists


Ring bone


Inflammatory Joint Disease


Route of Infection:

Most common in farm animals, specially the young where its a common sequel to neonatal bacteremia Non-infectious arthritis occur most often in dogs and
cats and have an immune- mediated etiology.


Common bacteria isolated from septic arthritis

 Trueperella (Arcanobacterium) pyogenes – cattle and swine

 Erysipelothrix rhusiopathiae – swine, sheep, birds
 E. coli – calves, piglets
 Streptococcus suis – pigs 2-10 weeks old

 Haemophilus suis and parasuis - 5-12 weeks old pigs
 Mycoplasma hyorrhinis –pigs 3-1o w

Mycoplasma hyosynoviae – pigs more than 10 weeks old

 Histophilus somni - cattle

 Mycoplasma bovis - cattle
 Borrelia burgdorferi (Lyme disease), humans and dogs


Viral arthritis

Caprine Arthritis-Encephalitis (CAE): is a slowly progressive disease of goats caused by a retrovirus. The virus also produces a respiratory and neurologic syndrome. Joint lesions are characterized by a lymphocytic hyperplastic synovitis with the formation of carpal hygromas.

The hygromas are chronic lesions that appear as flattened cystic fluid-filled subcutaneous distensions over the cranial carpus. Usually there is no communication with the carpal joint or tendon sheath.

A high prevalence of hygromas and lameness in a goat herd is a characteristic feature of CAE.


Non-infectious arthritis

 Occur most often in dogs and cats and affect multiple joints (polyarthritis)

  Have an immune-mediated etiology (rheumatoid-like arthritis)

  The inflammation is in response to persistence of antigen in the synovial membrane of affected joints, likely the sequel of previous infection, or to the deposition in the synovium of immune complexes derived from inflammatory lesions elsewhere.

 Erosive and non-erosive forms are described



Malignant Neoplasms of Joints

• Arise from the synovial membrane

• Uncommon in dogs and very rare in other species

• Two types: BOTH RARE
Synovial cell sarcoma: malignant tumors arising from synovial fibrocyte


Histiocytic sarcoma: malignant tumors arising from cells of histiocytic phenotype, possible dendritic (Langerhans) cells present in the synovium.