Joint structure and function Flashcards
what are the 3 main functions of joints
to permit movement of segments relative to one another
to transfer forces between bones (energy absorption and dissipation)
to absorb shock through movement
what are the three types of joints classified based on the type of motion they allow
synarthroses
amphiarthroses
diarthroses
what are synarthroses + example
immovable joints
fibrous connective tissue to fix bones together
ex: skull sutures in adults
what are amphiarthroses + example
slightly movable joints
allow slight movement
ex: intervertebral disc
what are diarthroses + example
most movable joints
ex: hips, shoulders, knees, elbows
what are the 3 types of joints classified by type of articulation
fibrous joints
cartilaginous joints
synovial joints
what are fibrous joints + example
adjacent bones are connected by fibrous connective tissue
immovable
ex: skull sutures in adults
what are cartilaginous joints + example
bones are joints by hyaline cartilage or fibrocartilage
ex: pubic symphysis (usually rigid)
what are synovial joints + example
bones are not directly connected (facilitates indirect contact of the bones)
articulate through a joint cavity filled with lubricating fluid
most common and most movable
ex: knees, elbows, fingers, shoulders, etc
what are the components of a typical synovial joints
proximal and distal bone
articular cartilage
articular capsule (keeps everything together and forms outside boundary of the joint)
synovial membrane (holds synovial fluid)
joint cavity (contains synovial joint)
what type of behaviour does synovial fluid exhibit
thixotropic behaviour
- viscosity increases with increasing speed of applied load
- results in a shock absorbing effect
- higher resistance from proteins as they get closer together
what are the benefits from synovial fluid
reduces friction between opposing surfaces of cartilage through lubrication provided by lubracin
- boundaries of lubrication between the layers of cartilage = decreases effects of shear and normal stresses (less deformation of cells)
what happens when there is no lubrication in the synovial joint
allows a lot of movement and deformation of the cartilage
- results in fatigue / damage
what is a degree of freedom
direction that a joint can move (translate) or rotate
joint can have a max of 6 degrees of freedom
- 3 translations and 3 rotations
- most joints facilitate rotation (more common than translation)
how many DOF does a ball and socket have
3 DOF - rotations about 3 axes
how many DOF does a purely hinge joint have
1 DOF - rotation about 1 axis
how many DOF does a pivot joint have (C1-C2 vertebrae)
1 DOF - 1 rotation about longitudinal axis
how many DOF does a saddle joint have (between carpal and 1st metacarpal)
2 DOM - rotation about 2 axes
how many DOF does a plane joint have
2 DOM - translation in 2 planes
what is caused by limited joint ROM
impairs ability to perform tasks of daily living
decreases quality of life
can be used to inform prescriptions / interventions in PT
when can joint ROM change
ex: in different conditions such as stroke
- differences between paretic and non paretic side
- differences can get smaller over time (not permanent)
what is the difference between active and passive mocap markers
active - require power, give off specific frequency of llight so camera can track particular markers
passive - dont have any wiring, need to track
why is markerless tracking becoming more popular
beneficial in rehab and clinical settings
uses image tracking algorithm to dynamically look at motion
can do it retroactively with videos
what are the pros and cons of markerless tracking
pros - cheap, easily accessible, doesnt take up space, don’t need much expertise
cons - limited accuracy, not great at measuring distances (camera doesnt know how long something is), parallax error (when not looking at something straight on, their can be errors in the video)
