Arthrology Flashcards
What is archeology?
study of joints structure and function
What are articulations?
joints
Where do arrticulations occur?
where two or more bones meet
where bone meets cartilage
when bone meets tooth
How are joints classified?
structurally
functionally
How are joints structurally classified?
Presence of a cavity - some joints have articulating structures in contact with one another, others have a space between the articulating structures (synovial cavity)
Connective tissue - may be composed of collagenous fibrous tissue, cartilage, ligament or dense irregular tissue
What are the categories used when classifying structurally ?
Synovial joints – identified by a cavity
Fibrous joints – identified by connective tissue type
Cartilaginous joints - identified by connective tissue type
How are joints functionally classified?
degree of movement (not movement type)
What are the three categories used to functionally classify?
a) Synarthroses Immovable
b) Amphiarthroses Slightly moveable
c) Diarthroses
Freely moveable (Only synovial joints)
What are fibrous joints?
Held together by fibrous / collagenous connective tissue
• No synovial cavity
• Three subdivisions :-
-Sutures (seams)
-Syndesmoses (band)
-Gomphoses (bolt)
• Subdivisions due to different structures being involved in forming an articulation / differing degrees of movement possible
What are sutures?
- present in the skull
- thin layers of fibrous tissue connecting plates of bone
- immovable
- Irregular in shape
- become ossified in adult animals leading to fusion of the associated bones
What are syndesmoses?
-thicker bands of fibrous tissue
-Articulating bones greater distance apart
-allow a slight degree of movement
E.g. interosseous membrane between the large metacarpal and small metacarpal bones of the horses’ distal thoracic limb
What is gomphoses?
- dentoalveloar joints
- roots of teeth and the alveolar processes of the maxilla and mandible
- immovable
What are cartilaginous joints?
• Lacking a synovial cavity
• Held together by cartilage
• Two subdivisions of cartilaginous joints:-
Synchondroses
Symphyses
Difference between the two subdivisions:
• Type of cartilage that unites the articulation – (hyaline or fibrocartilage)
• Degree of movement that is possible between the articulating structures (none or slight)
What are synchondroses?
Articulations united by hyaline cartilage
• Immovable
• Epiphyseal plates are main example - plates of hyaline cartilage connecting the diaphysis (long middle section) and epiphysis (short end sections) of long bones
• Ossify when growth ceases
• Joint is then referred to as a synostosis (joint united by
bone).
What are symphyses?
Articulations involving hyaline and fibrocartilage
Slightly moveable
Ends of the bones are covered in hyaline cartilage
Flat disc of fibrocartilage unites the articulating structures
Located along the midline of the body
Examples include intervertebral joints and the pubic symphysis
What are synovial joints?
Articulations where there is a synovial cavity
Held together by an articular capsule composed of dense irregular connective tissue and ligaments
All similar in structure
Classified as diarthroses
How are synovial joints classified?
type
movement they allow
What are the six subdivisions of synovial joints?
arthrodial trochoid ellipsoid sellaris spheroid ginglymus
What are the key structures found within synovial joints?
synovial cavity
synovial fluid
articular capsule
articular cartilage
What is the synovial cavity?
space located between the articulating bones of a synovial joint
purpose is to enable the joint to be freely moveable
What is synovial fluid?
Normal synovial fluid is viscous and clear/pale yellow in colour
Composed of hyaluronic acid secreted by the synovial membrane
Plus interstitial fluid filtered from blood plasma
What is synovial fluid?
Fills the synovial cavity and has three main purposes;
- Lubricates the joint and reduces friction
- Maintains the ‘health’ of the chondrocytes (cells of cartilage) within the articular cartilage by supplying nutrients / removing waste products
- Contains phagocytes which to maintain joint health by removing foreign bodies
Viscosity varies with exercise (sticky to watery)
Volume present within joint varies with joint size and activity (up to 40 cm3)
What is the articular capsule?
connective tissue enclosing the synovial cavity
composed of two layers; inner and outer
inner layer is the synovial membrane
outer layer is dense, irregular connective tissue
synovial membrane is composed of areolar tissue
Where unsupported it may form depressions
- Joint surface of membrane is highly folded
- Articular capsule stabilises the articulating bones
• May also be adipose tissue (‘fat pads’) within the synovial
membrane.
What is articular cartilage?
• Articulating surfaces covered in a 1-5mm layer of hyaline cartilage (articular cartilage)\
• Usually white / blue in colour
( may turn yellow with aging)
- Properties of hyaline cartilage provide a smooth surface (minimal friction) plus a shock absorber
- Composed of an organic matrix (type II collagen), chondrocytes, a solution of proteoglycans (PG’s), water, inorganic salts and glycoproteins
- PG’s consist of a protein core with around 150 glycosaminoglycan (GAG) chains attached
• Two different GAG found – keratan sulphate and chondroitin sulphate
(NB joint supplement contents)
• Articular cartilage is isolated with no blood, lymph or nerve supply
Cartilage attaches to subchondral bone via a calcified layer
• Subdivided into three zones – superficial tangential zone (STZ), middle zone, and deep zone
How does articular cartilage help mechanically?
- Biomechanically the PG’s and collagen are the important components
- Collagen provides tensile strength whilst PG’s provide compressive strength
- Subchondral bone also helps as a shock absorber
- The fluid component of the cartilage is also important
Cartilage acts similarly to a sponge full of water
- Water will be squeezed out or absorbed dependent upon the loading of the tissue
- Usually only a very small area of cartilage is actually loaded
- May have to withstand forces up to several times an animal’s bodyweight
What are synovial fossae?
- Synovial fossae appear in the articular cartilage of many species (areas of endochondral bone which are ‘naked’ of cartilage and covered only by a thin layer of connective tissue)
- Their role is unclear (?distribution of synovial fluid)
How do nerves and blood supply aid the articular capsule?
Articular capsule and the ligaments contain many nerve endings
- Innervated by the nerves that supply the voluntary striated muscles
- Innervated parts of the joint can sense pain and responds to the amount of movement and stretch of a joint
All structures are supplied by the circulatory system except articular cartilages
- Supplied by capillaries from arteries located adjacent to them
- Adjacent veins are responsible for removal of waste products
Articular cartilage is avascular and reliant upon synovial fluid for nutrition
• Lack of nerve supply means lesions usually become severe before an animal exhibits any outward signs
What are the synovial joint accessory structures?
Extra and intracapsular ligaments
Articular discs / menisci
Bursae
What do synovial joint accessory structures do?
provide stability
reduce friction
maintain joint health and physiology
What are extra and intra articular ligaments?
- Extracapsular = outside the articular capsule
- Stabilise joints e.g. medial and lateral collateral ligaments of the horses’ hock joint
- Intracapsular = inside the joint
- Provide added stability
- Folds in the synovial membrane mean that these ligaments, whilst lying inside the articular capsule, are not actually inside the synovial cavity
- E.g. cruciate ligaments within the stifle joint.
What are Articular discs/ menisci?
Some synovial joints contain fibrocartilage discs / menisci
• Located between the articular surfaces
• Attach to the joint capsule
• Often divide the synovial cavity in two
• Purpose is to modify the shape of a bone’s surface to enable bones to more tightly fit together
• Also help to stabilise joints and to distribute synovial fluid E.g. the stifle joint
What are bursae?
Fluid filled sacs located between skin and bone, tendon and bone, muscle and bone, and ligament and bone
• Found in any area where there may be friction (‘rubbing’) between bone and soft tissues
• Not part of joints but are located near to them
• Structure resembles that of the articular capsules
What are the synovial joint types?
categorised on the type of movement they allow • arthrodial (planar) • trochoid (pivot) • ellipsoid (condyloid) • sellaris (saddle) • spheroid (ball and socket) • ginglymus (hinge)
What are arthrodial joints?
‘gliding and sliding’ movements
Also referred to as nonaxial joints as the movements produced do not occur about an axis
Bones forming arthrodial joints have generally fairly flat articular surfaces
Examples include the carpus and tarsus
What are trochoid joints?
One bone provides a protrusion that fits into the ring of another bone
Allows rotational movements about an axis in one direction (also called monaxial)
Main example is the atlanto-axial joint
What are ellipsoid joints?
Formed where one bone has a convex-oval shaped articular surfaces that articulates with a concave-oval shaped articular surface of another
Biaxial allowing side to side and back and forth movements
Examples include the radiocarpal and midcarpal joints
What are sellers joints?
Formed where one bone has a ‘saddle’ shaped surface which articulates with another bone that fits into it like a rider would
Really modified ellipsoid joints
Biaxial
Examples include the inter and distal interphalangeal joints
What are spheroid joints?
Formed when one bone forms a ‘ball’ that articulates into a ‘socket’ of another
• Mulitaxial (enable movement in 3D)
• Examples include the shoulder and hip joints
What is a ginglymus joints?
Uniaxial
Enable ‘opening and closing’ movements
Examples include the elbow and fetlock joints
What are the possible movements made by animal joints?
- Gliding
- flexion
- extension
- adduction
- abduction
- rotation
What are gliding movements?
- Takes place in arthrodial joints ,e.g. the carpometacarpal joint
- Side-to-side, back-and-forth movement
- Bones do not change angle.
What is flexion?
- Flexion results in a decrease in joint angle
- Usually occurs in a sagittal plane
- Can occur in spheroid, ginglymus, ellipsoid and sellaris joints
- Some joints can dorsiflex or plantar flex
- Dorsiflexion = foot bends towards the dorsum
- Plantar flexion = foot bends towards the ground surface / sole of the foot
What is extension?
- Opposite of flexion
- Increase in joint angle
- Some joints may hyperextend (extend beyond their ‘normal’ anatomical position)
- Hyperextension can commonly occur at the horses’ fetlock joint
What is adduction?
- Movement of a joint towards the midline
- Usually in the frontal plane
- Shoulder and hip joints are capable of adduction
what is abduction?
- Opposite of adduction
* Movement of a joint away from the midline
What is rotation?
Movement of a bone around a longitudinal axis
• Where rotation occurs in the limb it may be described as
lateral or medial rotation
• Example is the radioulnar joint of the elbow in humans and canines
What is range of motion?
The range of motion (ROM) = distance in which joint can be moved in degrees
What is range of motion effected by?
ROM is affected by the:-
structure / shape of bones involved strength of associated ligaments associated muscles
use
What factors affect ROM?
Structure / Shape of Bones Involved
• How closely articulating bones fit together determines the type and range of movement possible
• Spheroid joints allow greatest ROM.
Strength of Associated Ligaments
• The greater the tension in the ligaments associated with a
joint, the smaller the ROM.
Associated Muscles
• Tension within muscles restricts ROM
Use
• Lack of use of a joint leads to a loss of ROM
How does age effect joints?
- Age has a number of effects on joint structure and function
- Articular cartilages undergo thinning
- There is a reduction in the amount of synovial fluid produced
- Shortening / tightening of ligaments
- Combination of these factors leads to a loss of ROM and a gradual degeneration of the joint structures
- Speed of change will be affected by use (‘wear and tear’), gender and genetics.
What is osteochondritis dissecans OCD?
• Lesion of the cartilage
• Loose portion of cartilage breaks off leaving
loose tissue in the joint; joint mouse.
• X-rays or arthroscopy are needed for diagnosis
• Causes pain from joint mouse and/or exposed bone
• Usually the joint is flushed to remove fragments, anti- imflammatories and pain relief needed
• More often seen in younger animals
What is osteoarthritis?
Most common form of arthritis in humans and companion animals
• Characterised by progressive deterioration and loss of articular cartilage
• Affects load-bearing synovial joints causing pain, inflammation and loss of mobility
• Osteophytes
(bone spurs) can form
What factors affect osteoarthritis?
- Age
- Obesity
- Joint trauma
- Joint instability
- Genetics
- Metabolic disease
- Endocrine disease
What is synovitis?
- Inflammation in the synovial membrane
- Can be a secondary condition of osteoarthritis
- Can also be caused by excess of joint fluid (effusion) or trauma to the joint
What is joint infection?
• Usually only caused by trauma when the integrity of the joint is compromised allowing dirt and bacteria into the joint capsule.
