Arthrology

what are the three major structural categories of joints?

fibrous, cartilaginous, synovial

what are the characteristics of fibrous joints?

aka synarthroses or syndesmosis

do not move much

no joint capsule

united by dense, fibrous connective tissue

ex: sutures of the skull, distal tibiofibular articulation

what are the characteristics of cartilaginous joints?

aka amphiarthroses or synchondrosis

move slightly

characterized by no joint capsule

held together by cartilage

generally fibrocartilaginous tissue (sometimes called hyaline cartilage) joins

motion limited

ex: intervertebral disc, pubic symphysis

what are the characteristics of synovial joints?

aka diarthrosis

freely moveable

motion dictated by the shape of the bones on the joint surface and by supporting soft tissue, i.e. muscle attachments and joint capsules (ligaments)

movements are described traditionally by the actual direction the bones move and the axis about which they move, this is called osteokinematics

what are the six elements of a synovial joint?

1. joint cavity (articular cavity)

2. articular cartilage (hyaline)

3. synovial membrane

4. fibrous capsule

5. synovial fluid

6. ligaments

what is osteokinematics?

motion of the joint surfaces

what is arthrokinematics?

motion of the joint surfaces

hinge joint

uniaxial - move in one plane - DIP

condyloid/ellipsoid

biaxial - move in two planes - MCP, radiocarpal

ball in socket joint

triaxial - move in three planes - glenohumeral (shoulder), coxofemoral (hip)

gliding or planar joint

translation - limited ROM but moves in all directions - AC joint, intercarpals, facet joints of spine

saddle joint

rare, triaxial - carpometacarpal joint of the thumb

pivot joint

uniaxial - rotation - atlas/axis - superior and inferior radioulnar

what is active motion?

produced by muscle contractions

muscles can move the same joint in a variety of ways depending on what is being stabilized

typically movement is described as the insertion moving toward the origin when contraction occurs

reverse muscle action

when the distal end is fixed - origin can move toward the insertion

what is a concentric contraction?

muscle fibers shorten during an activity

what is an eccentric contraction?

when a muscle lengthens during the contraction (sometimes called negative)