Key Terminology & Definitions - Musculoskeletal II Flashcards
Fibrous joint
United by fibrous tissue (little movement); e.g. sutures (skull), syndesmoses, and gomphoses (periodontal ligament of tooth root)
Sutures
= Cranial sutures, fibrous joints that connect the bones of the skull
Syndesmosis
Complex fibrous joint between two bones and connected by ligaments + strong mem, slight movement e.g. distal tibiofibular syndesmosis/inferior tibiofibular joint
Gomphosis
Fibrous mobile peg-and-socket joint e.g. periodontal ligament (tooth root) + alveolar bone
Cartilaginous joint
Union consists of either hyaline or fibrocartilage or a combination, sub-types = synchondrosis, symphysis
Synchondrosis
Primary cartilaginous joint mainly found in developing skeleton e.g. growth plates
Symphysis
Fibrocartilaginous joint in which the physis (body) of one bone meets the body of another all but two of the symphyses lie in the vertebral (spinal) column, all but one contain fibrocartilage as a constituent tissue
Synovial (diarthrodial) joint
Hyaline articular cartilage, articular capsule, joint space with synovial fluid (ligaments, fibrocartilaginous menisici, more complex, involved in supporting structures, most common joint
Articular cartilage synovial joint anatomy
Has loops of type II collagen embedded in hyaluronic acid matrix, no blood vv. or nerves in cartilage
Joint capsule synovial joint anatomy
Continuous with periosteum
Subchondral bone synovial joint anatomy
More deformable than normal bone, shares load when weight bearing, joint diseases makes bone denser - more strain on cartilage and worse damage e.g. esteosclerosis
Synovial membrane
Comprised of two types of synoviocytes, synovial fluid should be clear, colourless to light yellow + viscous
Type A synoviocytes
Macrophage-like, phagocytose and degrade debris
Type B synoviocytes
Produce synovial fluid (hyaluronic acid and glycosaminoglycans)
Intervertebral disc
Provides elasticity and shock absorption (buffer)
Nucleus pulposus
Intervertebral disc component - water and proteoglycans, few collagen fibres (fluid),
Annulus fibrosus
Intervertebral disc component - collagen fibres and some fibrocartilage (+ hyaline cartilage)
Degenerative joint disease (DJD)
= Osteoarthrosis/degenerative arthropathy, 1^y and 2^y gross lesions are identical (any joint/articular incongruence/misalignment will turn into DJD
Monoarticular
One joint
Polyarticular
Multiple joints
Primary DJD
Inevitable consequence of ageing, no predisposing cause, common incidental finding at PM in old animals
Secondary DJD
Due to an underlying abnormality or injury in the joint, cartilage degenerates prematurely
Osteosclerosis
Abnormal inc in density + hardening of bone
Osteochondromatosis
Benign neoplasm involving synovial mem, cartilage develops by metaplasia of connective tissue cells of mem
Osteophyte
Bony lumps/spurs
Eburnation
Painful bone-on-bone contact causing polishing of articular the surface (complete loss of articular cartilage)
High motion joint e.g. + DJD
Gradual cartilage erosion, subchondral bone sclerosis, chronic synovitis + joint capsule fibrosis -> stiffening e.g. metacarpophalangeal (fetlock) - most commonly affected by DJD, distal interphalangeal joint (coffin joint)
Low motion joint e.g. + DJD
Maximum loading is focused on a small area -> full-thickness cartilage necrosis with limited wearing, can result in ankylosis e.g. hock, proximal interphalangeal joint (pastern joint)
Ankylosis
Abnormal stiffening + immobility of joints due to fusion of the bones
Ringbone
DJD of interphalangeal joints, most common in forelimbs, older horses, early lesion is joint capsule fibrosis, progresses to osteophyte formation + ankylosis later
High ringbone
DJD of proximal interphalangeal joint (pastern joint)
Low ringbone
DJD of distal interphalangeal joint (coffin joint)
Spavin
Gross changes in tarsal/metatarsal, usually on medial aspect, starts as fibrous ankylosis and progresses to bony ankylosis
Bog spavin
Excess synovial fluid in early tarsal DJD (occupying larger area)
Bone spavin
Firm swelling due to bone remodelling in chronic tarsal DJD
Navicular syndrome
Loss of articular cartilage and bone resorption of distal sesamoid bone, periarticular osteophytes form, bone resorption follows nutrient arteries, usually forelimbs, bilateral
Chondrodystrophic breeds
Short legs, long backs e.g. Dachshunds, Basset hounds
Intervertebral disc disease (IVDD)
Mainly dogs, faster in chondrodystrophic breeds, collagen content of nucleus pulposus increases and decrease of proteoglycans with age
Disc herniation
Two types (Hansen type I & II), both usually dorsal (thinner annulus fibrosus than ventral)
Hansen type I IVDD
Massive extrusion of disc material into spinal canal, almost exclusively w/ chondrodystrophic breeds w/ disc degeneration, all discs are mineralised but usually only one herniate, may damage vessels leading to haemorrhage, ascending myelomalacia in some cases, extruded disc promote inflammation, can adhere to dura mater.
Non-chondrodystrophic breeds - can occur due to trauma but liquid disc means milder damage (Hansen type III)
Malacia
Softening and necrosis of nervous tissue - complete loss of architecture and cells
Hansen type II IVDD
Bulging of annulus fibrosis causing protrusion into spinal canal, non-chondrodystrophic breeds, obesity, nucleus pulposus stays mucoid until middle or old age, won’t degenerate, degeneration of annulus fibrosus allows slow protrusion of the disc, common in areas of high vertebral mobility, no rupture and no extrusion of contents = milder clinical signs
Areas of high vertebral mobility
Thoracolumbar region - distal/caudal thoracic vertebrae + cranial lumbar vertebrae
Spondylosis (or spondylosis deformans, ankylosing spondylosis (multiple vertebrae), bridging spondylosis
Osteophytes form along ventral vertebral bodies and can bridge between them, due to degenerative changes in ventral annulus fibrosus (stretching and tearing), dogs, bulls (+ rams + pigs)
Osteochondrosis
Failure of endochondral ossification, 3 forms, typically associated with initial necrosis within growth plate/articular epiphyseal cartilage complex, young, growing animals, often bilaterally symmetrical, regions of thickened, depressed, wrinkled cartilage due to collapse of necrotic cartilage, later can form a cleft that separates the cartilage from the bone -> cartilage flap, can break off into joint cavity = painful
Cervical myelopathy ‘wobbler’ syndrome
Horses + dogs - articular facet of vertebrae can predispose this, two forms, grossly thickened ligamentum flavum (ventral aspect of neural arches) + dorsal lamina, articular facet osteophytes
Cervical myelopathy - static form
Horses + dogs - show clinical signs w/o flexion/extension, articular facets are displaced ventromedially (towards spinal canal)
Cervical myelopathy - dynamic form
Horses only - clinical signs when neck flexed
Hip dysplasia
Lack of conformity between the femoral head and acetabulum -> joint laxity + DJD, large/giant dog breeds common, joint subluxation in dogs, sporadic cases in other species (e.g. Hereford cattle), lesions most prominent on weight-bearing areas or femur and dorsal acetabulum, femoral head becomes flattened and neck of femur thickens, formation of marginal osteophytes may make acetabulum look deeper than it is
Atlantoaxial subluxation
Small breed dogs - odontoid process of axis fails to fuse with body, dens is too small (severe dorsal displacement), corrected via surgery
Patellar luxation
Common in dogs, infrequent in horses, rare in other species, unilateral or bilateral, variable severity, joint instability predisposes to DJD
Patellar luxation - dogs
Usually medial luxation, small breeds (lateral luxation less common, usually seen in larger breeds), defects in stifle angle and direction of tension on patellar ligament, once patellar is out of the groove, it remains shallower and worsens risk of luxation and DJD
Patellar luxation - horses
Congenital hypoplasia of lateral ridge of trochlea, heritable in miniature horses, ponies
Synovitis
Inflammation of synovial membrane
Tenosynovitis
Inflammation of synovial joint + adjacent tendon sheaths
Arthritis
Inflammation of synovial membrane and other components of joint
Osteoarthritis
Inflammation secondary to degenerative joint disease
Pannus
Covers e.g. entire articular surface / formation, erosion of joint margins = granulation tissue
Infectious inflammatory joint disease
Young livestock, horses, sequel to systemic disease (neonatal bacteraemia) e.g. cystitis, generally affects multiple joints (polyarthritis) + may have osteomyelitis, penetrating wounds
Fibrinous arthritis
Bacterial - fibrin clots, abundant turbid synovial fluid, villous hyperplasia, articular cartilage not affected unless covered by pannus (granulation tissue) , pannus -> adhesions + ankylosis. early lesions may have periarticular oedema, chronic = lymphplasmacytic e.g. group A streptococci, erysipelas
Suppurative/purulent arthritis
Abundant neutrophils (degenerate + non-degenerate) in synovial fluid + membrane, more destructive than fibrinous arthritis, causes cartilage destruction at weight bearing areas, articular margins, if cartilage erodes, infection can get into underlying bone -> cartilage separation + ulceration + involvement of subchondral bone (epiphysis = osteomyelitis) Septic arthritis (bacteria) = degenerative neutrophils Non-degenerate neutrophils = mycoplasma, Borrelia, some viruses Non + degenerate neutrophils = immune-mediated arthritis
Diskospondylitis
Inflammation of the vertebral disc + associated vertebrae, due to primary bacteraemia, large breed dogs (lumbosacral, Staphylococcus pseudintermedius), pigs (upper thoracic, upper lumbar, erysipelas, T. pyogenes, staphylococci, Brucella suis), early lesions = soft, grey-yellow, extend into spinal canal/bone, later = disc destroyed, fibrosis, osteophytes
Erysipelas rhusiopathiae
Pigs (pig to pig transmission) - fibrinous polyarthritis, vacc inc risk
Lambs (omphalitis, tail dock/castration infection) - fibrinopurulent polyarthritis, high morbidity/low mortality
Steptococci
Calves - no obvious joint swelling - sub-clinical, PM to isolate pathogen
Lambs - polyarthritis (second most common behind erysipelas)
Pigs (S. suis) - purulent arthritis (uncommon)
Escheria coli
Calves - poly arthritis, tenosynovitis
Staphylococci
Livestock (S. aureus) - polyarthritis
Dogs (S. aureus) - monoarticular - foreign body disease/trauma
Pigs (S. hyicus) - fibrinopurulent (elbow, tarsus)
Haemophilus parasuis
Pigs - polyarthritis (Glasser’s disease) = fibrinous/fibrinosuppurative
Histophilus somni
Lambs - fibrinopurulent
Cattle - fibrinous, affects one or two joints
Borella (Borrelia burgdorferi = Lyme disease)
Dogs - intermittent arthritis involving one or more joints, lymphplasmacytic synovitis (non-specific), infection more common than disease
Chlamydophila pecorum
(Only chlamydia that causes arthritis in animals)
Calves - polyarthritis, usually fatal systemic disease
Lambs - high morbidity/low mortality, joint stiffness resolves with exercise (self-remission)
Mycoplasma
Livestock - polyarthritis, persistent antigen causes inflammation long after agent is gone
Pigs (M. hyorhinis > M. hyosynoviae) - fibrinopurulent polyarthritis
Goats > sheep - fibrinopurulent arthirits, hyperplastic synovitis
Cattle (M. bovis) - sporadic arthritis in any age group, half of feedlot cattle with M. bovis pneumonia also have fibrinosuppurative arthritis
Caprine arthritis and encephalitis virus (CAEV)
Transmitted in colostrum and milk, virus damages vascular supply to synovial structures, infection more common in goats w/ variable morbidity, lameness, high prevalence of carpal hygromas (chronic flattened, fluctuant, subcutaneous distention over cranial carpus full of yellow or bloody fluid +/- fibrinous clots), don’t typically communicate w/ tendon sheath, thickened joint capsule +/- mineral, joints distended by clear yellow fluid (carpus, stifle), villous hypertrophy, cartilage erosion, pannus, lymphoplasmacytic arthritis
Hygromas
Fluid-filled sacs that develop as a result of repeated trauma or pressure over a bony prominence
Fungi (inflammatory joint disease)
Dogs (blastomycosis, Histoplasma capsulatum, Coccidiosis immitis, cryptococcus neoformans, Sporothrix schenkii) - occasional cause of pyogranulomatous arthritis
Protozoa (inflammatory joint disease)
Dogs, cats (Leishmaniasis) - other manifestations more typical
Bursae
Fluid-filled pockets at regions of friction, can be part of normal anatomy (synovial) or acquired (adventitious), important in horses (nuchal ligament and underlying bursae)
Cranial nuchal bursae
Between atlas and nuchal ligament (horses)
Caudal nuchal bursa
Between axis and nuchal ligament (horses)
Supraspinous bursa
Between spinous process of T2 and nuchal ligament (close to saddle area) (horses)
Bursitis
Inflammation of the bursae, infectious (Actinomyces bovis, streptococci, staphylococci, Brucella abortus)/non-infectious (sterile = trauma, less likely to fistulate to surface)
Fistula
Abnormal connection
Poll evil
Inflammation of the cranial/and or caudal nuchal bursa
Fistulous withers
Inflammation of the supraspinous bursa
Adventitious bursae
From outside the joint capsule over bony prominences subjected to trauma (similar to sterile seroma), horses (capped elbow (olecranon, capped hock (tuber calcaneus), ruminants (carpal bursitis (hygroma), dogs (elbow hygroma), pigs (capped hocks), can be inflamed but not primary inflammatory lesions
Seroma
Build-up of clear fluid, not at a pressure point
Immune-mediated polyarthritis (IMPA)
Dogs + cats - can resemble infectious arthritis, non-degenerative neutrophils, hocks, carpi, stifle predisposed, erosive (cartilage destruction) and non-erosive (cartilage spared) forms
Erosive IMPA
Rare (1% of cases), greyhounds, immune complexes deposit in synovium and cause complement fixation, inflammation + degradation of cartilage matrix e.g. rheumatoid arthritis
Rheumatoid arthritis
Formation of rheumatoid factor = antibodies to immunoglobulins, rare in animals but can affect dogs -> destruction of cartilage + bone
Non-erosive IMPA
Most common, usually idiopathic, young, large breed dogs, antigen-antibody complexes deposit in synovium + recruit lymphocytes + neutrophils (pleocellular inflammatory response), no cartilage erosion, four types, can be vaccine/drug-induced - brief
Type I non-erosive IMPA
Uncomplicated - most common, source of complexed unknown
Type II non-erosive IMPA
Reactive - associated with distant infection or inflammation
Type III non-erosive IMPA
Enteropathic - associated with gastrointestinal or hepatic disease
Type IV non-erosive IMPA
Associated with carcinomas, leiomyosarcoma, lymphoma
Familial shar pei fever
Non-erosive IMPA - due to mutation caused inc hyaluronic acid production = characteristic folds. degradation of hyaluronic acid triggers immune system -> cyclic fever, pain, hock swelling (periarticular cellulitis +/- articular inflammation) (23% affected)
Hyaluronic acid
Substance found in the fluids in the eyes and joints - acts as a cushion and lubricant in the joints and other tissues
Systemic lupus erythematosus (SLE)
Non-erosive IMPA - uncommon, associated with signs of disease elsewhere e.g. cutaneous disease/visceral involvement, LE cells can be present in synovial fluid = pink material, displaces nucleus to periphery
Lupus erythematosus (LE) cells
Neutrophils with partly degraded phagocytosed nuclear material
Histiocytic sarcoma
Most common joint tumour in dogs, less common in cats, DC/type A synoviocyte origin, disseminated or local forms, chronic joint inflammation predisposes its development, stifle > elbow, shoulder, coxofemoral joint, carpus, tarsus, soft multilobulated tan mass infiltrating into join + surrounding soft tissues, vacuoles on cyto (malignant)
Synovial myxoma
Second most common joint tumour in dogs, seen in cats, stifle, digit >tarsus, elbow, carpus, vertebral facets, soft white translucent nodules that extend into surrounding tissues, slow growing, produces abundant viscous fluid, benign but can cause bony lysis (neoplastic osteolysis), soindle cells with a lot of myoxid matrix, middle-aged, large breed dogs predisposed, long history of clinical signs before diagnosis
Myoid
Connective tissue that looks more blue or purple compared to normal connective tissue on histo
Synovial chondromatosis
Osteochondromatosis if nodules ossify (have both components, bone + cartilage), shoulder > digits, elbow, tarsus, can transform to chondrosarcoma, hard pearly nodules attached to synovium but some can detach, large breed dogs, males, cats, horses, pigs
Primary synovial chondromatosis
Develops spontaneously, no underlying cause, more nodules than 2^y
Secondary chondromatosis
Develops due to degenerative joint disease (cartilage fragments break off and lodge in synovium or synovium undergoes chondroid metaplasia)
Synovial cyst
Rare, periarticular cavity lined by synovium + containing synovial fluid, usually communicate w/ joint space + associated joint has DJD, due to herniation of synovium from joint space, old cats around elbow, sometimes digits, dogs - spine + compresses SC, horses, digital flexor tendon sheath (superficial/deep), sometimes spine
Ganglion cyst
Contain viscous fluid but no synovial lining
Kyphosis
Excessive outward curvature of spine
Lordosis
Inward curve of the lumbar spine
Scoliosis
Abnormal lateral curvature of the spine
Chondrones
Chondrocyte cells at the periphery of damaged joint that have proliferated to form clusters + secrete matrix
Synovial pannus
Arises from synovium at joint capsule insertion line, may arise from subchondral capillary bed beneath ulcerated articular surface, increased O2 tension from capillaries kills chondrocytes while inflammatory mediators destroy matrix -> flat sheet of granulation tissue
Sclerosis
Hardening of tissue due to overgrowth of fibrous tissue and other changes
Spontaneous osteoarthritis (OA)
Can occur early in equine athletes, or later in older horses, arthroscopic grading systems (carpus, fetlock) + biomarkers related to macroscopic and histologic cartilage lesions
Osteochondrosis pigs
V. common, usually latens Dorsal acetabulum Humeral head Humeral condyles Occasionally physes Medial femoral condyle
Osteochondrosis in horses
One of most common predisposing causes for Wobbler syndrome - cervical vertebrae instability (cervical articular facets)
Lateral trochlear ridge, medial femoral condyle, patella
Distal tibia, tarsus
Fetlocks
Young, active (due to repeated trauma)
Osteochondrosis in dogs
Young, male, large breed
Humeral head
Osteochondrosis in cows
Lateral trochlear ridge Tibiotarsal joint Occipital condyles (lesser prevalence) Humeral head Elbow Distal radius
Canine rheumatoid arthritis
Unknown cause, immune-mediated (humoral and cell-mediated immunity) - AB (rheumatoid factor) of IgG or IgM produced in response to unknown stimulus, factors involve steric configuration of IgG, persistent bacterial cell wall components that cross-react w/ normal proteoglycans, anticollagen antibodies + defective suppressive T lymphocyte activity, characterised by exuberant pannus formation
Joint subluxation
Results as joint margins are reduced
Joint ankylosis
Occurs in high-load/low-motion joints
