Joints Flashcards
Joint
the junction of bones
Ligaments stabilize the joint by…
connecting the bones
Extra-articular ligaments
found outside of the joint capsule
Example of extra-articular ligaments
the collateral ligaments
Intra-articular ligaments
found within the joint capsule
Example of intra-articular ligaments
cruciate ligaments
Joint capsule
surrounds the joint
What is the joint capsule comprised of?
2 layers
-the outer layer - fibrous portion
-the inner layer - synovial membrane
Outer layer of the joint capsule
provides strength to capsule and may be connected to the collateral cartilages
Inner layer of the joint capsule
-responsible for amount and composition of the synovial fluid
-has some capacity to remove debris from the synovial fluid (phagocytosis)
-contains nerves
Where does pain in a joint usually stem from and why?
issues with the synovial membranes because it contains nerves
Physical characteristics of synovial fluid
-clear/slightly yellow
-viscous
-slippery
-thick
What are the two important compounds in synovial fluid?
-hyaluronan
-lubricin
What is the function of synovial fluid?
-reduces friction within the joint
-provides nutrients to articular cartilages (especially important because blood supply to cartilage is minimal and decreases with maturity)
What is the viscosity of synovial fluid determined by?
the amount of hyaluronan
-the more hyaluronan, the more viscous/thick
Articular cartilage
covers the ends of the opposing bones in a joint
Hyaline cartilage
-smooth
-whitish
-shiny
-slippery
-low friction
-minimal vascularization
Major components of articular cartilage
-mostly water (allows some resilience to compression)
-collagen
-proteoglycans (hyaluronan and aggrecan)
-chondrocytes (maintain, renew cartilage slowly; there are not many of them)
How well do articular cartilages heal?
not good if at all
The 4 zones of articular cartilage:
-superficial (tangential zone)
-Transitional (middle zone)
-radial (deep zone)
-subchondral bone
Superficial (tangential) zone
top layer, right below the synovial fluid
-sideways fibers
-hard
-should endure the force of back and forth movement
Transitional (middle) zone
has water, collagen, chondrocytes, and proteoglycans
-decompress and absorb concussion
Radial (deep) zone
bottom layer (seaweed looking)
-has uncalcified and calcified cartilage
-right on top of the subchondral bone and anchors to the bone
Tidemark
the edge between the uncalcified and calcified cartilage
Subchondral bone
bony material under the cartilage
-the calcified zone anchors the articular cartilage to the subchondral bone
Synovitis
inflammation of the synovial membrane (joint effusion)
What are the causes and symptoms of synovitis?
-over use, trauma
-increased production of synovial fluid (swelling-effusion; decreased viscosity)
-heat and pain
Bog spavin
synovitis of the tibial tarsal joint (swelling on the dorsal aspect)
Septic arthritis
infection in a joint (VERY BAD)
Septic arthritis causes and symptoms
-puncture, laceration, surgery or injections
-heat, pain, swelling
-usually starts with synovitis followed by cartilage damage (arthritis)
-needs to be treated right away
Osteoarthritis
degenerative joint disease (often a progressive disease)
Osteoarthritis starts with:
synovitis
-brings inflammatory cells, compounds to the area (prostaglandins, cytokines, enzymes)
-increase in blood flow, heat
-increase synovial fluid (lower in viscosity than normal)
After synovitis in osteoarthritis:
Cartilage damage
-if synovitis gets worse or continues
-enzymes, inflammatory cells, etc
-degrade collagen
-the superficial layer of the articular cartilage is damaged
-loss of normal smooth shiny structure (pitted, grooved, yellow, soft; function is affected)
Eventually after cartilage damage in osteoarthritis:
Subchondral bone damage
-severe articular cartilage damage
-damage may penetrate deep layers of cartilage
-subchondral bone may be affected
-severe inflammation, pain
After subchondral bone damage in osteoarthritis:
there is reduced joint function
-joint capsule is thickened
-collateral ligaments may lose flexibility
-decreased synovial fluid
-flexibilty reduced, chronic pain
At osteoarthritis’ worst:
there is loss of joint function
-articular surface (subchondral bone) can adhere to opposing articular surfaces
-“ankylosing” arthritis – joint fuses
-no joint flexibility
-may be less painful though
Bone spavin
boney growth
-horse will have less movement in the joint
-hock
-cartilage can wear away and bones fuse together
Osselet
-in the fetlock
-over time cartilage wears down and boney growth occurs
-usually the horse has synovitis when first beginning
Goals of osteoarthritis treatment
-reduce further damage and preserve joint function
-prevent permanent damage to the articular surfaces, deeper layers, ligaments, and bones
Reducing further damage from osteoarthritis includes:
-rest (reduce exercise, evaluate work load/surface/hoof care/etc.)
-control inflammation
How to control inflammation for osteoarthritis:
-cold therapy
-nonsteroidal anti-inflammatory drugs (NSAIDS)
-steroidal anti-inflammatory drugs (corticosteroids)
-interleukin-1 receptor antagonist protein (IRAP)
NSAIDS
used systemically (oral, IV, or IM administration)
Common NSAIDS
-phenylbutazone (bute) - oral or IV (not IM)
-flunixin (banamine) - oral, IV, or IM
Bute and Banamine
inhibit prostaglandin production by inhibiting “cyclo-oxygenase” enzyme (COX)
-not specific inhibition may have some side effects (typically GI irretation)
COX-II inhibitor (equioxx)
NSAID that acts only on COX enzyme involved in inflammatory prostaglandin synthesis
-fewer side effects, more expensive
Steroidal anti-inflammatory drugs (corticosteroids)
may be used systemically (goes everywhere)
-commonly used intra-articularly for OA
-reduce inflammation by inhibiting a different phase of the inflammatory cascade than NSAIDS
Common corticosteroids:
-cortisone
-dexamethasone
-can suppress some immune functions
-some can have negative affects on cartilage health
Interleukin-1 receptor antagonist protein (IRAP)
-reduces inflammation by inhibiting interleukin 1 (IL-1) (a pro inflammatory cytokine)
-a biologic produced from autologous blood (horse’s own blood processed to make IRAP)
-administered intra-articularly
Ways to restore/preserve joint function
-hyaluronic acid
-polysulfated glucosaminoglycans (PSGAGS)
-Pentosan Polysulfate
-Biologics (PRP and stem cells)
-polyacrylamide hydrogels
Hyaluronic acid
-intra-articular or systemic
-enhance lubrication in joint (improve viscosity and reduce friction, may decrease inflammation via physical effects)
Polysulfated Glycosaminoglycans (PSGAGS)
-systemic, possibly intra-articular
-can improve cartilage health
-can improve lubrication
-decrease inflammation
-Adequan (injectable IM)
Pentosan Polysulfate
-systemic, IM
-may enhance chondrocytes and synoviocyte activity
-support cartilage repair
-maintain normal synovial fluid composition
-reduce inflammation
-slow progression of OA
Biologics
-Platelet rich plasma (PRP) – autologous blood, intra-articular, reduce inflammation, may stimulate repair?
-stem cells – autologous cells, intra-articular, reduce inflammation, may stimulate repair?
Polyacrylamide Hydrogels
substances previously used in cosmetology
-intra-articular injection
-integrates into some joint tissues
-may restore some joint flexibility
-increase lubrication/reduce friction
-reduce inflammation
