Joints Degenerative - Pathology
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Degenerative joint disease (DJD)
- Osteoarthritis, osteoarthrosis
- Due to acceleration of normal ageing process - wear and tear
- Destructive disease leading to:
- Loss of weight-bearing articular cartilage
- Erosion, fibrillation of cartilage
- Clefts in the cartilage, perpendicular to the surface
- Complete exposure of underlying bone
- Bone appears polishes, dense - eburnation
- Radiographically - joint space reduction due to loss of cartilage
- Osteophyte formation at joint margins
- Remodelling of adjacent bone
- Brown/yellow discolouration
- Synovial hypertrophy
- Capsular fibrosis
- May affect one or multiple joints
- May or may not be symptomatic
- Pathogenesis:
- Not entirely clear but linked to loss of proteoglycans and subsequent lubrication
- Increased water content due to improper binding -> softening of cartilage = chondromalacia
- Predisposing factors:
- Persistent trauma
- Joint instability / dysplasia
- Conformational abnormalities / congenital malformations
- Osteochondrosis dissecans
- Intra-articular fractures
- Calve Legg-Perthe's disease
Luxations and subluxations
Patellar
- In stifle joints of dogs and horses
- Possibly inherited
- Small dog breeds:
- Medial luxation
- Due to underdevelopment of medial femoral condyle
- Large dog breeds and horses:
- Lateral luxation
Atlantoaxial
- In dogs, calves, horses and goats
- Miniature dog breeds:
- Failure of fusion of odontoid process to rest of axis
- Calves:
- Aplasia or hypoplasia of odontoid process
Temporomandibular
- In dogs, particularly Basset Hounds, Irish Setters
- Normal movement of mandibular coronoid process is interfered with by zygomatic arch
- Happens on one side -> open jaw locking
Calve Legg-Perthe's disease
- Almost exlusively in small dogs, particularly terriers and poodles
- Clinical signs appear at age of 4-11 months
- Grossly:
- Aseptic ischaemic necrosis in central parts of femoral head
- Possibly due to occlusion of blood vessels
- Fragmentation of trabecular bone
- Collapse of femoral head
- Revascularisation of femoral head
- Formation of new bone and osteophyte formation around femoral head and acetabular rim prior to old bone reabsorption
- -> severe degenerative arthropathy
- Aseptic ischaemic necrosis in central parts of femoral head
Degenerative arthropathy
- In older dogs (8+ years)
- Occurs bilaterally
- In shoulders
- ?Due to gradual atrophy of muscles with age -> joint laxity
Traumatic injuries
- Sudden
- Varying severity
- Acute injuries:
- Sprains
- Minor - resolved without any consequences
- More severe may result in persistent capsular and ligament laxity -> degenerative arthrosis -> impaired function
- Subluxations
- Luxations
- Intra-articular fractures
- Fracture healing may cause discontinuity of the articular surfaces
- Puncture wounds to foot may allow infection to travel to joints, bursae and tendon sheaths
- Haemorrhage into joint
- May occur in animals with clotting defects without special trauma
- Usually polyaricular
- Recurrent
- May cause pitting of articular surfaces -> degenerative arthrosis
- May occur in animals with clotting defects without special trauma
- Sprains
Nutritional diseases
Hypervitaminosis A
- See metabolic diseases of bones
- May cause spondylosis of cervical vertebrae
- Mainly on dorsolateral surface
- Also in elbow and shoulder joints -> fixation of joint
- May resolve with changes of diet
Disc protrusion
- Occurs mainly in dogs
- Almost always dorsal protrusion due to eccentric position of nucleus pulposus
- Main sites are cervical and lumbar regions
- Thoracic vertebrae have conjugal ligaments
- Degeneration precedes protrusion (two patterns):
- Chondroid
- In chondrodystrophic breeds
- Concurrent calcification of degenerated nucleus pulposus
- Progressive loosening and fragmentation of overlying annulus fibrosis fibres
- Damaged by both compressive and rotational forces
- Predisposing degeneration of the discs occurs by one year of age in most of the dogs
- Protrusion usually occurs in males, 3-6 years of age
- Sudden complete protrusion -> severe damage to spinal cord in the area
- Widespread necrosis and haemorrhage
- Extruded material is gritty, hemorrhagic or “cheesy”
- Fibroid
- In non-chondrodystrophic breeds, horses, pigs
- Usually occurs later in life
- Pathogenesis:
- Progressive dehydration and collagenisation of nucleus pulposus
- Fraying and fragmentation of lamellar annulus fibrosis fibres
- -> Attempts to repair by fibrosis
- -> Weak area in the annulus
- -> Partial protrusion (rarely may calcify) of nucleus into spinal canal
- May be dorsal or lateral
- -> Pressure on spinal cord
- -> Demyelination of white matter
- -> Progressive weakness of structures innervated distally to the lesion
- Disk material may enter blood vessels causing fibrocartilagenous embolism
- May present without any disk symptoms
- Chondroid
- Sudden protrusion can occur in any breed due to traumatic compression of spinal cord
Cervical spinal stenosis
- Usually funnel-shaped
- Stenosis in dorso-ventral plane
- May occur at more than one site
- Predisposed in some breeds: Great Dane, Doberman, Basset Hound, Irish Wolfhound, Old English Sheepdog
- Clinical signs: cervical pain -> ataxia -> quadriplegia
Cervicospinal arthropathy
- = "Wobbler" in horses
- Usually presents in first two years of life
- Mainly in fast growing thouroughbreds
- Most common site is C3-C4, can occur anywhere
- Abnormal laxity between the vertebrae + cervical vertebral malformation may be evident
- Osteophyte formation at edges of synovial components of joint
- Some due to stenosis of neural canal later in life (1-4 years of age)
- Clinical signs:
- Ataxia - hindlimbs more affected
- Presumed cause is rapid growth
Spondylosis
- Often in bulls and dogs, occurs also in horses, cats and pigs
- Osteophyte formation on ventral aspect of vertebrae
- Often around lumbar region
- Adjacent to intervertebral spaces
- Varies in size - small spurs -> 'bridges' between vertebrae
- May extend over few vertebrae
- Pathogenesis:
- Repeated abnormal movement between joints -> stress
- -> Degeneration of annulus fibrosis
- -> Osteophyte formation
- In dogs usually no symptoms
- In bulls may cause inability to mount
- In severe cases repeated damage may progress to recurrent posterior weakness and ataxia in conjuction with fractures of spondylitic and vertebral bone
Cranial cruciate ligament rupture
- Autoantibodies against collagens seen in the joint fluid – no relationship to the disease (ie: not an autoimmune disease) – can be seen in any joint disease
Steroid arthropathy
- From glucocorticoids injected into joint as antiinflammatories
- Injection sometimes causes rapid progression of degeneration
- Glucocortyicois suppress anabolic effect of chondrocytes -> reduction of cartilage matrix syhthesis -> proteoglycan depletion -> slower repair