4.1 joints and motion

what role do joints play in the human body

joints are places where two or more bones meet , they allow movement , provide stability , and help support the boy

how are joints classified by structure

fibrous ( synarthrosis is the functional classification ) : bones connected by connective tissue , do not move much ex : skull sutures

cartilaginous ( amphiarthrosis is the functional classification ) : bones connected by cartilage , allow little movement , ex : joints between vertebrae

synovial ( diarthrosis is the functional classification ) : have a fluid filled joint cavity that acts as lubricant and allow for most movement , ex : knee & shoulder

flexion

bending a joint , decreasing the angle

extension

straightening a joint , increases the angle

hyperextension

extending beyond the normal anatomical positon

abduction

moving away from the bodys midline

adduction

moving toward the bodys midline

rotation

turning a bone around its axis

circumdiction

moving in a circle

dorsiflexion

pointing the foot upward toward the shin

plantar flexion

pointing the foot downward

pronation

rotating the forearm so the palm faces down

supination

rotating the forearm so the palm faces up

different types of synovial joints

hinge , ball and socket , pivot , gliding , saddle , condyloid

hinge joint

moves mostly in one direction , elbow and knee

ex : elbow , knew

pivot joint

allows rotation around a axis

ex : between c1 and c2 vertebrae in neck

gliding joint

bones slide past each other

ex : wrist bones

ball and socket joint

moves in many directions , including rotation

ex : shoulder , hip

saddle joint

allows movement in two main directions

ex : base of thumb

condyloid joint

allows movement in directions , but little or no rotation

ex : metacarpophalangeal

role of cartilage in a joint

covers the end of bones , reduces friction , absorbs shock

what role does tendon play at a joint

connect muscles to bones , and transmit force that moves bones

what role does ligament play at joints

connect bones to other bones and help stabilize joints

what is range of motion

how far a joint can move in a particular direction , can be measured using a goniometer

goniometer

measures range of movement

how do bones , muscles , and joints work together to enable movement

bones provide support and act as levers . joints connect bones and allow movement . muscles contract and pull on bones through tendons , causing movement at joints .

ACL

prevents the tibia from sliding too far forward relative to the femur . also helps control rotation . connects lateral femoral condyle to anterior tibia

MCL

located on medial knee , connects tibia to femur , prevents knee from sliding inward too much

LCL

located on lateral knee , helps prevent knee bending outward too much , connects femur to fibula

varus

outside of knee

valgus

inside of knee

valgus stress test

tests the MCL , inner knee ligament

varus stress test

tests LCL , outer knee ligament

anterior drawer test

tests acl , whether shin bone moves too forward

posterior drawer test

tests PCL , if shinbone moves too far backward

PCL

prevents tibia from sliding too far backward relative to femur , connects medial femoral condyle to posterior tibia