Joints

articulations (joints)

a joint (articulation or arthrosis) is a point of contact between two or more bones, between cartilage and bones, or between teeth and bones

arthrology

the scientific study of joints

classification of joints

structural classification

functional classification

functional classification

based on the degree of movement permitted

synarthrosis

amphiarthrosis

diarthrosis

synarthrosis

completely immovable

e.g. suture of the skull

manubriosternal joint

amphiarthrosis

slightly moveable

cartilaginous

e.g. intervertebral disc

diarthrosis

freely moveable

synovial joints

also contains accessory ligaments and articular discs (menisci)—pads of fibrocartilage

diarthrosis classification

uniaxial

biaxial

multiaxial

uniaxial diarthrosis

allows movement within a single anatomical plane or axis of motion

e.g. elbow joint

biaxial diarthrosis

allows for movement along two planes or axes

e.g. metacarpophalangeal joint

multiaxial diarthrosis

hip and shoulder joints

structural classification

based on the presence or absence of a synovial (joint) cavity and type of connecting tissue

classified as:

fibrous

cartilaginous

synovial

fibrous joint

dense irregular connective tissue

lacks a synovial cavity

have the articulating bones held together by fibrous connective tissue

permits little to no movement

types include:

sutures

syndesmosis

gomphosis

suture fibrous joint

composed of a thin layer of dense fibrous connective tissue that unites skull bones

synostosis

synostosis

a suture joint that has ossified

e.g. the frontal suture between the left and right sides of the frontal bone

functionally classified as a synarthrosis

syndesmosis fibrous joint

more connective tissue than in a suture

can form a wide fibrous joint where the shafts of two parallel bones are connected by a broad interosseous membrane

e.g. tibiofibular joint

gomphosis fibrous joint

dentoalveolar

a cone-shaped peg fits into a socket

dense irregular connective tissue—periodonatal ligament

degeneration of gums

periodontal ligament and bone = periodontal disease

e.g. the root of a tooth in its socket

cartilaginous joint

dense regular connective tissue

lacks a synovial cavity

has the articulating bones connected by either fibrocartilage or hyaline cartilage

allows little or no movement

two types:

synchondroses

symphyses

synchondrosis cartilaginous joint

the connecting material is hyaline cartilage

symphysis cartilaginous joint

the connecting material is a disc of fibrocartilage

e.g. interverterbral discs and pubic symphysis

synovial joint

has a synovial (joint) cavity between the articulating bone and are freely moveable (diarthrotic)

types of synovial joints

plantar

hinge

pivot

condyloid

saddle

ball and socket

articular cartilage

covers the bones at synovial joints

reduces friction at the joint with movement and helps absorb shock

torn cartilage

occuring frequently in the knees of athletes

damage to the articular discs that lie between the ends of some bones

removal to prevent erosion and arthritis is accomplished by arthroscopy

techniques for cartilage replacement

alternative knee replacement

in cartilage transplantation chondrocytes are removed from the patient, grown in culture, and then placed in the damaged joint (autologous chondrocyte implantation)

articular capsule

surrounds a diarthrosis, encloses the synovial cavity, and unites the articulating bones

composed of two layers:

• outer fibrous capsule

• inner synovial membrane

other capsule features include ligaments and articular fat pads

outer fibrous capsule

may contain ligaments

inner synovial membrane

secretes a lubricating and joint-nourishing synovial fluid

synovial fluid

secreted by the synovial membrane

lubricates and reduces friction in the joint and supplies nutrients to and removes metabolic wastes from the joint

when disease or injury leads to a buildup of synovial fluid, the fluid may be aspirated and medications may be injected into the cavity

ligaments

help hold bone to bone

extracapsular ligaments

intracapsular ligaments

extracapsular ligaments

collateral ligaments

intracapsular ligaments

ACL

PCL

sprain

forcible wrenching or twisting of a joint that stretches or tears its ligament but does not dislocate the bone

strain

a stretched or partially torn muscle

articular discs

modify the shape of the joint surfaces of the articulating bones

help maintain the stability of the joint, and direct the flow of synovial fluid to areas of greatest friction

nerves

nerves that supply a joint are the same as those that supply the skeletal muscles that move the joint

blood supply

numerous arteries and veins supply the joints and surrounding structures

bursae

synovial fluid filled sac-like structures that cushion the movement of one body part over another

found where one part of the body moves over another

tendon sheaths

tubelike bursae that wrap around tendons where there is considerable friction, such as the tendon of the biceps brachii at the shoulder joint

bursitis

chronic inflammation of a bursae

gliding movements

when relatively flat bone surfaces move back and forth from side to side with respect to one another

no significant alteration of the angle between the bones

occurs at plantar joints

angular movements

an increase or decrease in the angle between articulating bones

principal angular movements are:

flexion

extension

hyperextension

flexion

results in a decrease in the angle between articulating bones

extension

results in an increase in the angle between articulating bones

lateral flexion

the movement of the trunk sideways to the right or left at the waist

occurs in the frontal plane and involves the intervertebral joints

hyperextension

a continuation of extension beyond the anatomical position and is usually prevented by the arrangement of ligaments and the anatomical alignment of bones

abduction

the movement of a bone away from the midline

adduction

the movement of a bone toward the midline

circumduction

the movement of the distal end of a part of the body in a circle

occurs as a result of a continuous sequence of flexion, abduction, extension, and adduction

condyloid, saddle, and ball-and-socket joints

rotation

bone revolves around its own longitudinal axis

pivot and ball-and-socket joints

medial rotation

the anterior surface of a bone of the limb is turned toward the midline

lateral rotation

anterior surface of a bone of the limb is turned away from the midline

elevation

upward movement of a part of the body

depression

downward movement of a part of the body

protraction

movement of a part of the body anteriorly in the transverse plane

retraction

movement of a protracted part back to the anatomical position

inversion

movement of the soles medially at the intertarsal joints so that they face away from each other

eversion

movement of the soles laterally at the intertarsal joints so that they face away from each other

dorsiflexion

bending of the foot at the ankle in the direction of the superior surface

plantar flexion

bending of the foot at the ankle joint in the direction of the plantar surface

supination

movement of the forearm at the proximal and distal radioulnar joints in which the palm is turned anteriorly and superiorly

pronation

movement of the forearm at the proximal and distal radioulnar joints in whcih the distal end of the radius crosses over the distal end of the ulna and the palm is turned posteriorly or inferiorly

opposition

movement of the thumb at the carpometacarpal joint in which the thumb moves across the palm to touch the tips of the finger on the same hand

plantar joints

side-to-side and back-and-forth gliding movements

nonaxial

intercarpal

intertarsal

sternoclavicular

acromioclavicular

sternocostal

vertebrocostal

hinge joint

the convex surface of one bone fitting into a concave surface of another bone

movement is primarily flexion or extension in a single plane

elbow

knee

ankle

interphalangeal joints

pivot joint

round or pointed surface of one bone fits into a ring formed by another bone and a ligament

movement is rotational and monaxial

atlas rotating about the axis and turning the palms anterior and posterior

condyloid joint

oval-shaped condyle of one bone fits into an elliptical cavity of another bone

movements are flexion-extension, abduction-adduction, and circumduction

joint between the carpals and the radius

saddle joint

contains one bone whose articular surface is saddle-shaped another bone whose articular surface is shaped like a rider sitting in the saddle

movements are flexion-extension, abduction-adduction, circumduction

ball-and-socket joint

ball-shaped surface of one bone fits into the cuplike depression of another

movements are flexion-extension, abduction-adduction, rotation, and circumduction

shoulder joint

hip joint

factors affecting contact and range of motion at synovial joints

structure and shape of the articulating bone

strength and tautness of the joint ligaments

arrangement and tension of the muscles

contact of soft parts

hormones

disuse

range of motion effects of aging

various aging effects on joints include decreased production of synovial fluid

a thinning of the articular cartilage

loss of ligament length and flexibility

due to genetic factors as well as wear and tear on joints

arthroplasty

surgical replacement of a joint with an artificial joint

most commonly replaced joints:

hips

knees

shoulders

rheumatism

refers to any painful state of the supporting structures of the body

bones

ligaments

joints

tendons

muscles

arthritis

form of rheumatism in which the joints become inflamed

rheumatoid arthritis

an autoimmune disease in which the body’s immune system attacks its own cartilage and joint linings resulting in loss of joint function

can lead to bony deformities, especially in the hands

osteoarthritis

a degenerative joint disease commonly known as “wear and tear” arthritis

characterized by deterioration of articular cartilage and bone spur formation

noninflammatory and primarily affects weight-bearing joints

ankylosing spondylitis

affects joints between the vertebrae and between the sacrum and hip bone

occurs often in men and in early adulthood

unknown cause

ankylosing spondylitis treatment

medication

physical therapy

rare cases surgery

gouty arthritis

a condition in which sodium urate crystals are deposited in soft tissues of joints, causing inflammation, swelling, and pain

if not treated, bones at affected joints will eventually fuse, rendering the joints immobile

most frequently injured major joint

the ankle

most common injury to the ankle

sprain

RICE

rest

ice

compression

elevation

pott’s fracture

fracture of the distal leg that involves both the medial and lateral malleoli