Lecture 12: Equine Osteoarthritis Flashcards
Where are the nerve endings in a joint capsule
Fibrous joint capsule
What does a flexion test do
Puts stress on fibrous joint capsule, aggregates nerves and can make lame limb more obvious
What is synovial fluid
Ultrafiltrate of plasma and secretions
What is the intima of synovial fluid
Made of synovial cells that act as a filter of what is going in and out of joint capsule
What does the subintima contain
Ground substance/ glycoaminoglycosides (GAG)
How does synovial effusion occur when joint swells
Intima space gets bigger and fluid leaks in faster than it can get removed
What is the appearance of normal synovial fluid
Vicious
What is the cell count of normal synovial fluid
<500/ul
What % do lymphocytes, monocytes and synovial lining cells make up for normal synovial fluid
90%
Neutrophils make up __% of normal synovial fluid
10%
Is there endogenous hyaluronic acid
Yes, 0.5mg/ml
T or F: synovial fluid clots
False, no clot no fibrin, unless swollen then fibrin will leak in
What layer maintains the tensile strength in the articular hyaline cartilage
Tangential layer
What layer of the articular hyaline cartilage maintains the cyclic deformation/squish
Radial layer
Healing of the joint/articular hyaline cartilage requires removal of what layer
Calcified cartilage
What makes up the ground substance
Glycoaminoglycans (GAGs) and proteoglycans
What type of strength do the more superficial layers of articular cartilage provide
Tensile strength
What type of strength do the deeper layers of articular cartilage provide
Compressive, stiffness (squish)
Describe the joint lubrication for low loads
Boundary lubrication from hyaluranon and lubricin- decreases friction
What structures provide joint lubrication for low loads
Synovial membrane, synovium-cartilage, cartilage-cartilage
Describe the joint lubrication at high loads
Hydrostatic (squeeze film) lubrication of cartilage-cartilage interface
Fluid will extrude from cartilage surface to go between cartilage surfaces and then fluid goes back in (why we need squish)
What provides structural support and is the primary shock absorber- protects articular cartilage
Subchondral bone
___takes away cushion and cartilage in damaged in subchodnral bone
Sclerosis
What are some inciting causes of DJD
- Direct injury
- Biochemical- inflammation, sepsis, iatrogenic (steroids)
What happens to cartilage in DJD
Loss of proteoglycans, becomes weaker, fibrillates and cracks, ground substance disappears
What is the end result of DJD
Osteoarthritis
How does OA appear on radiographs
- Narrowing of joint space
- Subchondral bone and periarticular changes- sclerosis, lysis/cystic lesions, periarticular osteophyte formation
Identify which is normal and which has DJD
Left: DJD, narrowing
Right: normal
Identify the general problem and then issues indicated by 1-3
OA- ringbone (high at pastern joint)
1. Joint narrowing
2. Subchondral sclerosis
3. Lysis
Identify the problem and where is it
Distal Tarsal OA (Bone spavin)
Loss of joint space, Subchondral bone sclerosis/lysis
What are some factors in DJD for abnormal stresses on normal cartilage
- Chondral/ osteochodnral injury
- Joint instability (collateral ligament tears)
- Steroid (MPA) injections
What are some factors in DJD that are normal stresses on abnormal cartilage
- Synovitis
- Capsulitis
- Osteochondrosis
what is wrong
P1 fracture
What is wrong and how can this contribute to OA
Collateral ligament tear- causing joint instability
What is wrong and how can this contribute to OA
Space where arrow is pointing is too big between carpal and intermediate carpal bones
Leads to joint instability
What is wrong here and what can it lead to that will contribute to OA
Distal tibial OCD- leading to synovitis
OCD is a very common cause of ___
Synovitis
What is wrong here and what can it lead to that contributes to OA
Chip fracture at P1- bone fragment will wiggle and create inflammation—> synovitis
What are the main players in synovial inflammation
- Synovial cell
- Chondrocytes
- PMN (especially with sepsis)
Which is normal vs abnormal, what is wrong. And use of what could have caused this?
Left: normal
Right: GAG loss due to steroids (Mehthylprednisolone acetate/ MPA
What is wrong here
cartilage fibrillation
What is wrong here
erosion of shoulder joint
T or F: limited capacity to repair articular cartilage in adults
True
T or F: hyaline cartilage can be replaced
False
What is hyaline cartilage replaced with
Cartilage defect granulation/ fibrous tissue fibrocartilage
Type 1 collagen (not as good as type 2)
What does this show
Fibrocartilage, due to repair from injury of articular cartilage
Fibrocartilage is important in repair of damage to joint/ articular cartilage because it…..
Seals the defect and stops the inflammation
Image on left had defect cartilage removed to expose ___ indicated by yellow arrow
Subchondral bone
How do you manage joint inflammation
- Prevention- conformation, foot care
- Exercise management
- Weight loss
What are the systemic medical management options for osteoarthritis
- NSAIDs- phenylbutazone, banamine
- Glucosamine
- DSMO IV
- Hyaluronic acid IV
- Polysulfated glycosamingolycans (adequan)
How do NSAIDS decrease inflammation
Inhibit arachidonic acid pathway by inhibiting COX
Corticosteroids can be used intra-articularly but cause ___depletion over time
GAG
What is the drug of choice for intra-articular steroids
Triamcinolone acetonide
How does triamcinolone acetonide work
Inhibit PLA2 in arachodonic acid pathway and suppresses inflammation
What is the maximum dose for traimcinolone per horse
18mg/horse
Steroid induce __can be observed with exceeding maximum
Laminitis
What steroid has significant GAG depletion
Methylprednisolone acetate (MPA)
MPA should not be used in what joints
High motion joints
___acid does not mitigate negative effects of MPA
Hyaluronic acid
Hyaluronic acid with ___or ___ does have chondroprotective effect
Triamcinolone and betamethasone
___with MPA is very harmful to cartilage
Lidocaine
What does hyaluronic acid do in joint
Anti-inflammatory
Steric hinderance of particles through synovium/ mesh filter/ intima
T or F: hyaluronic acid has negative effects on cartilage
False
What do polysulfated glycoaminoglycans (adequan) do in tx of joints
- Stimulate endogenous hyaluronic acid
- Increase proteoglycans and collagen synthesis by chondrocytes
- Inhibit metalloproteases
Intra-articular use of adequan must be given with ___because it potentiates joint infections
Amikacin
What is the mechanism of action of IRAP
Blocks IL-1
IRAP is made from
Horses own blood
T or F: IRAP has negative effects
False
PRP has ___proteins
Potent anti-inflammatory proteins
PRP is used more for __injuries
Ligament
PRP can cause post injection ___
Flare
What is post injection flare
Acute swelling/effusion and lameness immediate post injection to 24-48hrs
Chemical reaction to whatever you injected
What do you do for post injection flare
If continues to worsen 24-48hrs after injection lavage joint, put on hyaluronic acid and no steroids
