Lecture 2-3 1/24-27/25 Flashcards
What are the layers within a normal joint?
-articular cartilage
-subchondral plate
-cancellous bone
Why is it important that the chondrocytes change orientation within the articular cartilage?
-parallel chondrocytes on the surface help to resist shearing
-more vertical chondrocytes deeper in the cartilage allow for compression
What is the tide mark?
line differentiating more superficial non-calcified cartilage from deeper calcified cartilage
What are the components of a normal hip joint?
-joint capsule
-synovial lining layer
-acetabular fossa
-ligament of the head of the femur
What are the layers of the cartilage?
-non-calcified:
–articular surface
–zone 1
–zone 2
–zone 3
-tide mark
-calcified:
–zone 4
–osteochondral junction
-subchondral bone plate
What is released when proteoglycan breaks down?
chondroitin sulfate
What is cartilage loading?
when weight/pressure is applied to the cartilage, water is “squeezed” to the surface and the matrix is compressed
What absorbs water during cartilage unloading?
glycosaminoglycans
Which molecule is unique to articular cartilage?
type 2 collagen fibrils
What is the overall function of articular cartilage?
to provide a low friction system that helps resist abnormal wear
What is arthritis?
inflammation of the joint(s)
What are the common clinical presentations for arthritis?
-lameness
-difficulty ambulating
-decreased activity
What are the common clinical findings in arthritis?
-lameness
-joint effusion
-stiffness
-decreased activity
-decreased joint range of motion
-muscle atrophy
What are the clinical findings associated with inflammatory or septic arthritis?
-fever
-lethargy
-inappetence
-other systemic signs
Which conditions are considered non-inflammatory joint disorders?
-osteoarthritis/degenerative joint disease
-traumatic injury
-neoplasia
Which conditions are considered inflammatory joint disorders?
-non-infectious, immune mediated disorders
–erosive
–non-erosive
-infectious arthritis
What is the general diagnostic approach for arthritic patients?
-history
-physical and orthopedic examinations
-radiographs (before more invasive procedures)
-arthrocentesis
-CBC/serum chem/UA
-serologic testing for tick-borne disease
What is the technique for an arthrocentesis?
-clip and prep the area
-insert a 21g needle into the joint
-allow fluid to drip into a purple top/EDTA tube
-use syringe if necessary to aspirate fluid; increases red cell contamination
What are the characteristics of a normal arthrocentesis fluid?
-transparent
-very high viscosity
-low WBC count
-low PMNs/neutrophils
-high mononuclear cells
-healthy cells
What are the characteristics of an OA arthrocentesis fluid?
-transparent
-high viscosity
-lower WBC count
-low PMNs/neutrophils
-high mononuclear cells
-healthy cells
What are the characteristics of an erosive immune-mediated arthrocentesis fluid?
-clear or opaque
-low viscosity
-moderate WBC count
-moderate to high PMNs/neutrophils
-moderate to high mononuclear cells
-mainly healthy cells
What are the characteristics of a non-erosive immune-mediated arthrocentesis fluid?
-clear or opaque
-very low viscosity
-moderate to high WBC count
-moderate to high PMNs/neutrophils
-low to high mononuclear cells
-mainly healthy cells
What are the characteristics of a bacterial arthrocentesis fluid?
-opaque
-very low viscosity
-high WBC count
-high PMNs/neutrophils
-low mononuclear cells
-degenerate cells
What are the characteristics of osteoarthritis?
-changes that occur in all aspects of the “joint organ”
-synovitis leads to pain and sensitized nociceptors
-progressive degenerative changes lead to decreased structure and function of the cartilage and atrophy of articular tissues
What are the types of joint instability or trauma that can lead to OA?
-normal forces acting on an abnormal joint; secondary to developmental conditions
-abnormal forces acting on a normal joint; exogenous trauma
What are the clinical signs of OA?
-joint pain
-tenderness
-limitation of movement
-crepitus
-joint effusion
-inflammation without systemic effects
How is the integrity of articular tissue maintained?
a balance between destruction and production of cartilage matrix
What changes occur in OA that result in a loss of articular tissue integrity?
-increase in destruction of cartilage matrix
-initial mild increase in cartilage matrix production in response followed by a decrease in cartilage matrix production
-net loss of cartilage matrix
What happens when matrix is released into the synovial fluid?
the fragments are recognized as foreign invaders in the synovial fluid and a protective response develops against the fragments
What is the cycle of OA cartilage injury?
-proteoglycan degradation leads to catabolism and a loss of elasticity
-debris and enzyme release causes synovitis
-synovialcytes enhance inflammation and cause pain
What changes in the cartilage are seen with mild OA?
-surface irregularity
-cloning of chondrocytes
-sclerosis of bone
What change in the cartilage is seen with severe OA?
full thickness loss of cartilage; bone on bone
What is the pathogenesis of OA?
-mechanical and/or enzymatic damage disrupts collagen network and diminishes tensile stiffness
-alteration of proteoglycan content reduces stiffness further
-continued damage and degradation occurs; caused primarily by chondrocytes
What are the characteristics of OA presence?
-studies show nearly 60% of dogs are affected with OA
-most dogs are affected in more than one joint
-owners do not typically recognize when their pets have OA
-early identification is crucial for more effective treatment and improved mobility
Which conditions are examples of immune, non-erosive inflammatory arthritis?
-canine systemic lupus erythematosus
-polyarthritis/polymyositis
-idiopathic polyarthritis
-plasmacytic-lymphocytic gonitis
-drug induced arthritis (sulfas)
-vaccination induced arthritis
What are the characteristics of polyarthritis/polymyositis?
-non-septic suppurative synovitis
-multiple joint involvement
-generalized muscle inflammation
-occurs in spaniel breeds commonly
What are the characteristics of idiopathic polyarthritis?
-non-septic suppurative synovitis
-multiple joint involvement
-diagnosis of exclusion
-most common form of inflammatory polyarthritis
-can be caused by any antigen-antibody reaction
What are the types of idiopathic polyarthritis?
-type 1: isolated condition
-type 2: associated with other infections
-type 3: associated with GI disease
-type 4: associated with neoplasia of other sites
What is the signalment associated with idiopathic polyarthritis?
-no breed predilection
-no gender predilection
-more common in young adults
What is the clinical history associated with idiopathic polyarthritis?
chief complaint: shifting leg lameness
location: sometimes unsure
degree: variable; mild to non-ambulatory
onset: acute to subacute, potentially intermittent
past history: may be significant
general: lethargy and inappetence
What are the physical findings in idiopathic polyarthritis?
general: depressed +/- fever
gait: stiff, confused with neuropathic gaits
posture: painful, haunched, non-ambulatory
muscle: normal
bone: normal
joints: painful, effusive
What are the characteristics of synovial fluid analysis in idiopathic polyarthritis?
-turbid or cloudy
-low viscosity; thin and watery
-consistently elevated cell count
-mature non-toxic PMN leukocytes
-no bacteria
Which potential causes of polyarthritis need to be ruled out to diagnose idiopathic polyarthritis?
-ehrlichia
-rocky mountain spotted fever
-lyme disease
-heartworm
-bacterial infection
-drug-induced
-medical condition-induced
What are the steps of therapy for idiopathic polyarthritis?
-start with doxycycline
-if doxy does not cure condition, move on to steroid long-term and maintain
-if steroid does not work, combine steroid with chemotherapy and maintain
Which immunosuppressive drugs are used for immune-mediated joint disease?
-prednisone
-leflunomide
-azathioprine
-cyclosporine
-cyclophosphamide
What are the characteristics of plasmacytic-lymphocytic gonitis?
-effects canine stifle joint
-causes cranial drawer instability
-severe synovitis
-surgical stabilization likely needs to be combined with long-term anti-inflammatories
What are the characteristics of drug induced arthritis?
-associated with sulfadiazine-trimethoprim
-seen in doberman pinschers and other large/giant breeds
-may cause inappetance, fever, lethargy, and swollen joints
-discontinuing drugs leads to spontaneous improvement
What are the characteristics of vaccination-induced arthritis?
-post-vaccination
-spontaneous resolution
Which conditions are examples of immune, erosive inflammatory arthritis?
-canine rheumatoid arthritis
-late stage lupus
What are the characteristics of canine rheumatoid arthritis?
rheumatoid factor due to altered IgG
-antibody/antigen complexes are deposited in synovium and induce arthritis
-leads to cartilage erosion, subchondral lysis, and joint collapse/deformation
-pathologic dislocation
-characteristic external rotation of carpus and tarsus/seal walking
What can cause infectious arthritis?
-bacterial
-mycoplasma
-rickettsial
-protozoal
-fungal
-viral
What can lead to a bacterial infectious arthritis?
-direct infection
-hematogenous infection
-spread from surrounding tissues
What is the signalment of bacterial arthritis?
-no breed predilection
-no gender predilection
-immature if unknown source
-mature if endocarditis-related
What is the clinical history associated with bacterial arthritis?
chief complaint: lameness and depression
location: single leg
degree: severe; non-weight bearing
onset: acute
past history: not significant
What are the physical findings in bacterial arthritis?
general: depressed, fever > 104 deg. F
gait: non-weight bearing
posture: carries the leg
muscle: normal
bone: normal
joint: severely painful, effusive
What are the therapy steps for bacterial arthritis?
-drainage; open/surgical or closed
-antibiotics; long term, systemic treatment based on C&S
Which antibiotic class is used to treat polyarthritis associated with tick-borne disease?
tetracyclines
