Lecture 3: Disorders of the Joints

non-inflammatory joint disease

• developmental

• degenerative joint disease (DJD) → most common!

inflammatory joint disease

• infectious

• immune-mediated → primary idiopathic, reactive polyarthritis

common infectious DDx in dogs

• distemper

• bacteria → staphylococcus, streptococcus (most common)

• mycoplasma, bacterial L forms

• Borrelia burgdorferi

• leishmania

• tick borne → ehrlichia spp., RMSF, anaplasma spp.

common infectious DDx in cats

• calicivirus, feline syncytium-forming virus, feline infectious peritonitis

• bacteria pasteurella multocida, others (anaerobes)

• mycoplasma, bacterial L-forms

DJD

• chronic progressive disorder of joints

• articular cartilage damage and degenerative proliferative changes in the periarticular tissues

• any breed (C/F), any size and age can be affected

what are the most commonly identified underlying causes of DJD?

joint instability, trauma, and developmental orthopedic diseases

what is the most common location of DJD?

hips

clinical signs of DJD

• insidious onset of signs confined to the musculoskeletal system with no systemic signs

• lameness, stiffness, sometimes only after exertion, muscle atrophy

prevention and treatment of DJD

• weight management

• exercise and physical fitness

• pharmaceuticals

• physical rehabilitation

• complementary therapies

weight management for DJD

altered biomechanics associated with overweight/obese BCS or joint incongruity negatively affects normal movement → chronic pain and dysfunction

what NSAIDs are we targeting for OA?

COX-2

if NSAID ratio is < 1 =

COX-1 selective

if NSAID ratio > 1 =

COX-2 selective

what is the minimum washout period between NSAIDs?

72 hours

NSAIDs differ in their

potency, duration, and side effects

grapiprant

NSAID with unique mode of action → targets the EP4 receptor of PGE2

NSAIDs are ideal for long-term treatment due to

safety profile

all NSAIDs have the potential to cause

GI side effects ranging from gastric ulceration to erosion

do not use NSAIDs in these patients

dehydrated, hypotensive, concurrent steroids, geriatrics with co-morbidities

screen prior to NSAID tx

• good history and discuss adverse effects

• pre-treatment → CBC, chemistry, UA

• recheck bloodwork 7-14 days later then every 6 months

managing OA in cats

• NSAIDs use with extreme caution in cats (limited hepatic glucuronidation)

• meloxicam (Metacam, robenacoxib (onsior) are approved for use in cats but must be used with caution

• use judiciously as part of multimodal therapy plan

omega-6 fatty acids

linoleic acid → arachidonic acid → pro-inflammatory (eicosanoids, prostaglandins, leukotrienes, thromboxanes)

omega-3 fatty acids

alpha-linolenic acid → EPA → DHA → minimally inflammatory (eicosanoids) and inflammation resolving (resolvins, protectins)

good omega ratio

O6:O3 is 3:1, 4:1

omega fatty acids

• supplementation of EPA/DHA produces anti-inflammatory effects and helps break cycle of cartilage destruction

• supplementation through joint diets is more client friendly

oral formulations of OA agents

• glucosamine, chondroitin sulfate

• green lipped mussel

• pentosan

injectable formulations of OA agents

• polysulfated glycosaminoglycans

• hyaluronic acid

opioids for OA

• butorphanol (mild to moderate pain)

• methadone

• hydromorphone

• buprenorphine

• morphine

• tramadol (oral)

• fentanyl

novel adjunctives for OA

• ketamine CRI → NMDA receptor inhibitor

• amantidine → NMDA antagonist

• amitriptyline → TCA with pain modulating properties

• gabapentin → associated with NMDA receptors

• lidocaine

joint injections

• stem cell therapy, platelet rich plasma, autologous conditioned serum

• hyaluronic acid, corticosteroids

synovetin-OA

• uses radio-synovia-orthesis to break the cycle of pain and inflammation for chronic OA patients

• novel radioisotope is injected into the joint, engulfed by macrophages and synoviocytes, which causes apoptosis

newest drugs for chronic OA

• frunevetmab (cats) and bedinvetmab (dogs) → species-specific anti-NGF monoclonal antibodies

• 1x month injection

• not for acute or neurologic pain

route of infection of septic arthritis

• hematogenous

• direct inoculation → penetrating joint wounds are common, often resulting in single joint infection

• spread from local, adjacent tissue

what organisms are most common in septic arthritis in dogs?

staphylococcus spp, streptococcus spp and coliform organisms

what are the most common organisms for septic arthritis in cats?

pasteurella spp

septic arthritis is more common in

large-breed dogs

diagnosis of septic arthritis

• radiographs of affected joint

• arthrocentesis with joint fluid analysis

• aerobic and anaerobic cultures of joint fluid

goal for treatment of septic arthritis

rapidly resolve infection, decrease inflammatory compounds in joint (enzymes, fibrin)

treatment of septic arthritis

• start antibiotics as soon as cultures are collected

• initial choice pending culture and sensitivity should be broad spectrum, beta-lactamase resistant antibiotic

acute cases of septic arthritis can be managed

medically with caution

chronic infections, foreign bodies, immature animals with open growth plates should have

immediate surgical management

tick borne polyarthritis - Lyme

• borrelia burgdorferi → spirochete related to leptospira and treponema

• worldwide distribution

• 90% of lyme disease is diagnosed in 10 northeastern US states

what is the most common signs of Lyme in dogs?

lameness and/or myalgia

true or false: most dogs infected with Lyme are asymptomatic.

true

clinical signs of Lyme

• lameness and/or myalgia

• acute onset with lethargy, inappetence, ± fever, lymphadneopathy

• joint swelling in one or more joints, painful on palpation

how does Lyme affect joints?

• spirochetes colonize synovial membrane and activate IL-8, which is a potent chemotactic factor for neutrophils

• affected joints characterized by marked fibrin effusion, neutrophilic infiltration, thickened synovial membranes

• lymphocytes and plasma cells replace neutrophils in chronically infected joints

treatment for lyme

• history → recent tick exposure in an endemic region

• clinical signs

• positive serology

• prompt response to antibiotic therapy

tests for lyme

• ELISA → most commonly used screening test for antibodies, non-specific cross reactivity

  • IDEXX snap 4dx plus test (qualitative)

  • tests for antibodies against unique outer surface protein (C6 peptide)

  • does not react to vaccine-induced antibodies

for acute infections of lyme, treatment includes

• tetracyclines

• lactams

for chronic/refractory cases of lyme, treatment includes

• azithromycin

• 3d generation cephalosporins

steroid therapy for lyme

• should be used with caution

• low dose anti-inflammatory doses only

• immunosuppressive doses exacerbate infection

Rickettsial polyarthropathy

• RMSF caused by rickettsia rickettsii

• ehrlichia canis

• ehrlichia ewingii

• anaplasma phagocytophilum

polyarthropathy is largely due to

immune complex deposition in synovial membranes

CBC abnormalities for rickettsial polyarthropathy

thrombocytopenia common

RMSF is most likely to be associated with

more significant systemic disease due to vasculitis

diagnosis of tick borne polyarthritis

• screening serology

• fourfold rising IgG titer over 2-3 weeks

• joint taps with cytology may be useful, especially in acute phase of the disease course when serology is still negative

• PCR to confirm

• response to therapy

treatment of tick borne polyarthritis

• tetracyclines for 3 or more weeks

• concurrent glucocorticoid therapy if antimicrobial therapy alone does not eliminate the fever, lameness, and joint swelling

feline polyarthropathy

• mycoplasma gatea and mycoplasma felis

• bacterial L-form secondary to bite wounds

• septic arthritis secondary to foreign bodies or bite wounds

• infectious polyarthropathy is more common in cats than dogs

this 10-week old kitten has joint swelling and fever 1 week after MLV vaccination. Thoughts?

calicivirus

what accounts for 25% of all nonerosive immune-mediated polyarthritis cases?

reactive polyarthritis

reactive polyarthropathy

• chronic, bacterial, fungal, or rickettsial infections

• neoplasia

• drug administration

• numerous systemic diseases

idiopathic immune-mediated nonerosive polyarthritis is diagnosed only by

ruling out other causes of polyarthritis and it’s the most common form of polyarthritis in the dog NOT CATS

clinical signs of idiopathic immune-mediated nonerosive polyarthritis

cyclic fever, stiffness and lameness, multiple joints affected

diagnosis of IMPA

synovial fluid analysis, failure to ID other infectious causes

treatment of IMPA

empirical treatment with doxycycline while awaiting the results of synovial fluid cultures

treatment of IMPA

• rapid and complete response to antibiotics makes it unlikely IMPA

• cornerstone of therapy → prednisone

what is the most common polyarthritis in dogs?

IMPA

what is this showing?

joint effusion