Joint architecture

Joints

articulations

areas where adjacent bones/cartilage join

what do joints allow for

differential growth

transmission/distribution of forces

movement

classifying joints

anatomy/tissues

function

shape of bones

movement classification

cavitated/synovial = diarthroses

solid: synarthrosis OR amphiarthroses = no/very little movement

connective tissue classification

fibrous

cartilaginous(fibrocartilage, hyaline)

synovial

fibrous CT

collagenous junctions between bones

synarthrotic - no/little movement

sutures(skulls)

gomphoses(teeth)

syndesmoses(more widespread, interosseous membrane or aponeurosis)

sutures

skull, synarthrotic

CT between bones = membranous tissue(NEVER ossified)

sutural ligament interlocks bones VERY tightly

appearance: denticulate, serrate, squamous(overlap)

gomphosis

peg-and-socket

synarthroses

collagenous CT connecting dental cement with bone

syndesmosis

boney surfaces bound by interosseous membrane, fibrous cord, or aponeurotic membrane

amphiarthrotic(little movement)

includes distal tib-fib, middle tib-fib, middle radio-ulnar, intercarpal/intertarsal, posterior SI joint

cartilagenous joints

connected by cartilage

amphiarthrotic

subcategories: synchondrosis, symphysis

synchondrosis

primary cartilaginous joints: growth plate

CT between bones - hyaline

occurs at centers of ossification - growth plate

function primarily as differential growth mechanisms(temporary joints)

resists forces of compression, tension, shear, torsion

allows for slight bending early in life

between sternum and 1st rib(costochondral joints), developing os coxae

become synostoses when bone grwoth complete(fuse

symphysis

secondary cartilaginous joints

CT between bones: hyaline and fibrocartilage disc

located median in skeleton - pubic symphysis, intervertebral discs

amphiarthrotic

very strong

withstand compression, tension, shear, torsion forces

remain throughout life

technically may ossify and become a completed boney union(synostosis)

synovial joints

bones linked by fibrous(articular capsule with intrinsic ligaments, blends with periosteum

often associated with internal and/or external extrinsic ligaments

occasional articular discs or menisci

articulating surfaces covered by hyaline cartilage(osseous surfaces don’t touch directly)

contains synovial fluid to facilitate movement

diarthroses

intrinsic

part of the joint capsule

extrinsic

stand alone, not part of the joint capsule

internal

inside the joint capsule

external

outside of joint capsule

synovial joints contain

articular surfaces(really slick/slippery, becomes brittle with age)

fibrous/articular capsule

synovial membrane

synovial fluid - clear, lubricates, alkaline

intra-articular discs, menisci, labrum(shoulder and hip), fat pads(cushions), bursae, sheaths

classification of synovial joints

complexity of form

function(DOF)

shape

anatomic complexity of form - synovial

based on number of articulating surfaces and absence/presence of disc or menisci

simple: 2 articulating surfaces and no discs/menisci

compound: >2 articular surfaces

complex: presence of discs

compound complex is possible

DOF

1 DOF: 1 plane of motion, 1 axis …etc…

flex/ext, axial rotation, abd/add

shape of bone

plane, hing, pivot, condylar/ellipsoid, bicondylar, saddle, ball-and-socket

plane

flat articulating surfaces

pure translation or sliding between joints

intercarpals/tarsalsm

hinge/ginglymus

uni-axial

strong collateral ligaments

humeroulnar

pivot/trochoid

uni-axial

osseous pivot in osteo-ligamentous ring

rotation around pivot’s axis

radial head in annular ligament; odontoid process of axis(C2) with atlas(C1)

condylar/ellipsoid

bi-axial

oval convex male surface opposed to elliptical female concavity

generally little rotation due to articular shapes

radiocarpal, MCP

bicondylar

largely uni-axial

modified hinge

limited rotation

2 convex condyles articulating with concave surfaces

knee

saddle/sellar

bi-axial

convexity of larger is apposed to concavity of smaller

artiucular shape causes conjunct axial rotation

1st CMC(thumb), SC

ball & socket/spheroidal

reception of global head into opposing cup

multi-axial

glenohumeral, coxal

every joint has

vascular supply

lymphatic drainage

innervation

most joints have

ligaments

internal v external

intrinsic v extrinsic(part of capsule that is named vs separate structure from capsule)

joint limitations

tension of ligaments/fibrous capsule

tension of muscles

approximation of soft tissue

bone shape and contour