Osteoarthritis Flashcards
In which joints is arthritis worse
worse in small ‘tight’ joints such as tarsus or elbow, compared to large, ‘padded’ joints e.g. stifle or hip
worse in high motion joints such as antebracheocarpal joint vs low motion joints e.g. carpometacarpal
mechanism of arthritis
be a complex condition affecting the whole joint, in which activation of matrix proteases has a pivotal role
Cartilage, subchondral bone, and synovium probably all have key roles in disease pathogenesis, and an association with systemic inflammation could also be present.
What is the main protein of cartilage
type II collagen
provides a meshwork that receives stabilisation from other collagen types and non-collagenous proteins, such as cartilage oligomeric matrix protein, and provides cartilage with tensile strength
What is the purpose of aggrecan and other proteoglycans embedded in cartilage
draw water into the cartilage, providing compressive resistance
Role of chondrocyte in normal cartilage/joint
what do they release
Regulates cartilage architecture and biochemical composition in response to chemical and mechanical environment
They release inflammatory response proteins such as: cytokines (interleukin 1B, interleukin 6, TNFa) and matrix-degrading enzymes (metalloproteinases, ADAMTS (a disintegrain and metalloproteinase with thombospondin-like motifs))
Collagenases and aggrecan-degading ezymes are metrix-degrading enzymes important in pathology, others are beneficial in healthy cartilage
What are DAMPs
Damage-associated molecular patterns
Component of innate immune system
Proteins from damaged or dying cells due to trauma or an infection by a pathogen
Role of chondrocytes in osteoarthritis
The innate immune system is activated in osteoarthritis
Chondrocytes express many toll-like receptors, which are activated by DAMPs
Chondrocytes also express receptors that bind advanced glycation end products, which accumulate in ageing tissues which results in a phenotypic shift to catabolism and could help to explain the increasing prevalence of osteoarthritis with age.
The response to the extracellular matrix proteins reflects the amplification of established cartilage degradation.
Chondrocytes could first be activated by inflammatory signals originating from other joint structures such as synovium or subchondral bone.
what is the tidemark
The superficial layer consists of calcified cartilage, which is separated by the cement line (tidemark) from the deep layer of compact cortical bone
Role of subchondral bone in osteoarthritis
Subchondral cortical bone= interface between the calcified cartilage below the tidemark and the underlying trabecular bone.
In osteoarthritis, big changes are seen in structure and composition of cortical and trabecular bone plates
Features of endochondral ossification are reinitiated in osteoarthritis and the tidemark advances, with associated vascular penetration.
This process is accompanied by the formation of osteophytes and subchondral cysts. Subchondral bone is highly innervated and probably contributes to the generation of pain in disease.
Role of the synovium in osteoarthritis
Synovitis is a common feature of osteoarthritis, even in early disease.
In established osteoarthritis, proliferation of synoviocytes and tissue hypertrophy are notable, with increased vascularity.
Synoviocytes synthesise lubricants such as hyaluronic acid
and lubricin.
These contribute to optimum joint function but show reduced lubricating capacity in subsets of patients with osteoarthritis.
Synoviocytes, like chondrocytes and osteoblasts, also release inflammatory mediators and degradative enzymes.
Significance of prostaglandin E2 in OA
Increased in inflamed joints
Correlates with degree of lameness
Proteoglycan degradation and inhibition of synthesis
Example treatment plan for dog with OA
Baseline haematology & biochem (liver, kidney function)
Urinalysis, and film dog for reference
Analgesia:
Discuss dosing regime for NSAIDs or grapiprant
Daily chewable tablets or monthly for NSAIDs
Any previous problems with NSAIDs?
Mild liver/renal dz – might use grapiprant (EP4 Rc antag)
Weight loss & exercise & play & supplements:
1-2% weight loss per week
Feed 60% of usual amount, controlled exercise
Omega 3 supplements (takes time to work)
Home modifications & trim nails, clip fur between toes, rugs, ramps, 3 x 5 mins walk a day
Pain Assessment
Observation of behaviour is very subjective
Assign score to behaviour to make it more objective ??
Still considerable individual variability
In scorer
In animal
There is no “gold standard” pain scale yet
Use scales to ensure that animals are frequently checked and level of pain assessed
Adjunct to physical examination
Take into account individual variation
Assessing chronic pain
Chronic pain is multifactorial (mood, posture & movement domains) and subjective
Chronic pain scales will be made up of questions from these domains
Scales to monitor chronic pain in cats
Feline Musculoskeletal Pain Index (FMPI)
Client specific outcome measures (CSOM)
Montreal testing of cat arthritis (MI CAT C)
Montreal testing of cat arthritis (MI CAT V)
Health related quality of life questionnaires
