Joint structure and function

Question 1

what are the 3 main functions of joints

Answer 1

to permit movement of segments relative to one another
to transfer forces between bones (energy absorption and dissipation)
to absorb shock through movement

Question 2

what are the three types of joints classified based on the type of motion they allow

Answer 2

synarthroses
amphiarthroses
diarthroses

Question 3

what are synarthroses + example

Answer 3

immovable joints
fibrous connective tissue to fix bones together
ex: skull sutures in adults

Question 4

what are amphiarthroses + example

Answer 4

slightly movable joints
allow slight movement
ex: intervertebral disc

Question 5

what are diarthroses + example

Answer 5

most movable joints
ex: hips, shoulders, knees, elbows

Question 6

what are the 3 types of joints classified by type of articulation

Answer 6

fibrous joints
cartilaginous joints
synovial joints

Question 7

what are fibrous joints + example

Answer 7

adjacent bones are connected by fibrous connective tissue
immovable
ex: skull sutures in adults

Question 8

what are cartilaginous joints + example

Answer 8

bones are joints by hyaline cartilage or fibrocartilage
ex: pubic symphysis (usually rigid)

Question 9

what are synovial joints + example

Answer 9

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

Question 10

what are the components of a typical synovial joints

Answer 10

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)

Question 11

what type of behaviour does synovial fluid exhibit

Answer 11

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

Question 12

what are the benefits from synovial fluid

Answer 12

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)

Question 13

what happens when there is no lubrication in the synovial joint

Answer 13

allows a lot of movement and deformation of the cartilage
- results in fatigue / damage

Question 14

what is a degree of freedom

Answer 14

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)

Question 15

how many DOF does a ball and socket have

Answer 15

3 DOF - rotations about 3 axes

Question 16

how many DOF does a purely hinge joint have

Answer 16

1 DOF - rotation about 1 axis

Question 17

how many DOF does a pivot joint have (C1-C2 vertebrae)

Answer 17

1 DOF - 1 rotation about longitudinal axis

Question 18

how many DOF does a saddle joint have (between carpal and 1st metacarpal)

Answer 18

2 DOM - rotation about 2 axes

Question 19

how many DOF does a plane joint have

Answer 19

2 DOM - translation in 2 planes

Question 20

what is caused by limited joint ROM

Answer 20

impairs ability to perform tasks of daily living
decreases quality of life
can be used to inform prescriptions / interventions in PT

Question 21

when can joint ROM change

Answer 21

ex: in different conditions such as stroke
- differences between paretic and non paretic side
- differences can get smaller over time (not permanent)

Question 22

what is the difference between active and passive mocap markers

Answer 22

active - require power, give off specific frequency of llight so camera can track particular markers
passive - dont have any wiring, need to track

Question 23

why is markerless tracking becoming more popular

Answer 23

beneficial in rehab and clinical settings
uses image tracking algorithm to dynamically look at motion
can do it retroactively with videos

Question 24

what are the pros and cons of markerless tracking

Answer 24

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)