Degenerative Joint Disease Flashcards
What do joints allow for?
Predictable and energy efficient motion
-transfer of load
What properties of joints encourage joint stability?
Geometric shape of articular surfaces, ligaments, joint capsule, tendons, muscle, menisci, synovial membranes
Where are menisci present in the body?
At the stifle and the TMJ
Define osteoarthritis
Progressive and permanent deterioration of the articular cartilage
- a group of disorders characterized by deterioration of the articular cartilage, changes in the subchondral bone, and changes in the soft tissues of the joint
What are the main causes of OA?
Abnormal stress on normal cartilage
-due to joint incongruence, loss of stability (ligament tear or fracture) or athletic trauma
Normal stress on abnormal cartilage
-due to osteochondrosis, aging, synovitis
Describe the pathogenesis of OA
-abnormal stress on normal cartilage causes cell injury and direct damage to the cartilage matrix, leading to loss of PGs from matrix, enzymatic breakdown of PGs and collagen as well as decreased synthesis of PGS and collagen
-normal stress on abnormal cartilage causes the same as the above minus the losses from the matrix
-all of this leads to the morphological breakdown of articular cartilage
Describe how articular cartilage repairs itself
Not well- no cells for proliferation or blood supply
-it has a limited capacity for regeneration or healing
-natural repair processes by adjacent tissues are incapable of producing tissue with morphologic, biochemical and biomechanical properties of articular cartilage
-cartilage defect –> fibrous tissue –> fibrocartilage
-fibrocartilage is weaker–> will wear and byproducts will cause inflammation of the joint
What is the etiopathogenesis of OA?
Physical forces lead to biomaterial failure (traumatic injuries)
-chondrocyte response to insult (degradation and repair) leads to chronic synovitis
-extra cartilaginous factors cause secondary cartilage changes (bony remodeling, synovial responses, microfractures, vascular changes, and others)
What are the cytokines associated with OA produced by both the synovial membrane and bone that lead to inflammation associated with OA?
Interleukin 1 and TNF alpha
-these induce bone resorption, and inflammation in joint response
What other compounds are released by the synoviocytes when they are damaged?
Free radicals, prostaglandins and metalloproteinases, and aggrecanase (breaks down proteoglycans of cartilage)
Name some of the changes associated with OA in joints?
Swelling of the joint due to synovitis, trabecullar modelling of subchondral bone, erosion of cartilage, inflammation of joint capsule and structures around the joint, new bone formation (enthesophytes) and osteophytes
-goal of all of this is to fuse the joint-body does a poor job of this though
What are some of the first signs of articular cartilage degeneration?
Discoloration due to loss of PGs (turns yellow), fibrillation, erosion, wear lines, eburnation
What changes occur with degeneration of the articular cartilage?
Decreased prostaglandins, reduced PG aggregation with GAGS, increased or decreased water content, change in collagen structure
-all results in reduced compressive and tensile strength
What is the chondrocytic response in arthritis?
Normally chondrocytes maintain a balance between turnover of the ECM or the cartilage and synthesis
- in this case there are more enzymes created and less synthesis (more IL1 and TNF, less IGF and TGF)
How do mechanical factors contribute to the pathogenesis of OA?
They affect cartilage indirectly by insult to the subchondral bone, synovial membrane or chondrocytes
What happens to the subchondral bone in OA?
Thickens (sclerosis) leading to reduced shock absorption
-can lead to lysis- shear induced tensile failure of collagen cross-links
What are the targets in treatment of OA?
Reduce inflammation of the joints (synovitis)
-treat traumatic injury
-correct for developmental orthopedic disease
-prevent infection
Decrease inflammations of the soft tissues and cartilage, alleviate pain, lubricate joint, restore normal environment, improve cartilage repair
What are some challenges associated with medical management of OA?
Chance of success depends on specific joints involved, stage of lesions, work of horse, age of horse, finances, response to therapy and regulations for competing
What are the components of medical management in OA cases?
Exercise modification, weight reduction, anti-inflammatories, slow acting and disease modifying antiosteroarthritis agents, and supportive care
What are the levels of OA treatment?
Oral: supplements and systemic anti-inflammatories
Topicals: surpass
Injectables: hyaluronic acid, polysulfated glycosaminoglycans
Joint injections: corticosteroids, hyaluronic acid, polysulfated glycosaminoglycans, regenerative therapies
Name the nonsteroidals commonly used in horses
Phenylbutazone, flunixin meglumine, firocoxib, diclofenac sodium, acetaminophen (not a true NSAID- no side effects)
What glycosaminoglycan is FDA approved?
Adequan IM
What does adequan promote in joints? What does it inhibit?
Stimulates production of HA by synoviocytes, increases synthesis of proteoglycans and collagen by chondrocytes and inhibits metalloproteases
What are some advantages and disadvantages to intraarticular corticosteroids?
Advantages: decreases MMP, decreases IL-1, TNFa, decreases fibrin deposition, causes pain relief, cheap, helps with chondrocyte nutrition
Disadvantages: pain relief, laminitis