Shoulder joints Flashcards
what is the shoulder complex
an ensemble of bones, joints and soft tissue that must function synchronously
what is the center of activity and has dual function
GH joint
what are the dual functions of the GH joint
stability and mobility
what is the function of the shoulder
mobilize the hand in space
what does the design of the shoulder allow
for a large ROM
but this mobility presents conflict
we also need stability
articulation of the sternoclavicular joint
sternal end of the clavicle w/ the notch formed by the manubrium of the sternum and first costal cartilage
very incongruent joint
how is the SC joint incongruent
the articular surface of the clavicle is thicker than the articular surface of the manubrium
what type of joint is the SC joint
plane joint w/ 3 degrees of freedom of motion
although the joint is a plane joint, the surfaces are saddle shaped
how does the clavicle present w/in the SC joint in the frontal plane
the clavicle is convex w/in the frontal plane
how does the manubrium present w/in the SC joint in the anterior/posterior direction
the manubrium is convex w/in the anterior/posterior direction
how does the clavicle present w/in the SC joint in the anterior/posterior direction
the clavicle is concave w/in the anterior and posterior direction
how does the manubrium present w/in the frontal plane of the SC joint
the manubrium is concave w/in the frontal plane
how’re the manubrium and clavicle separated w/in the SC joint
fibrocartilaginous disc
what’re the functions of the sternoclavicular disc
- increase the motion b/w the articular surfaces
- acts as a shock absorber for forces that are transmitted from the lateral end of the clavicle
- improves joint stabilization by increasing joint congruity
motions of the SC joint
elevation
depression
protraction
retraction
upward rotation
downward rotation
elevation and depression occur
in the frontal plane around the sagittal axis
approximately how much can the SC joint elevate
45 degrees
approximately how much can the SC joint depress
5-15 degrees
where does protraction and retraction occur for the SC joint
transverse plane around a superomedial to inferomedial oblique axis
what is retraction @ the SC accompanied by
elevation
what is protraction @ the SC joint accompanied by
depression
(SC joint) protraction is the movement of
the distal clavicle anteriorly
(SC joint) retraction is the movement of
the distal clavicle posteriorly
how much pro/retraction can the SC perform
15 degrees
is rotation a true degree of freedom
no
where does rotation occur @ the SC joint
longitudinal axis of the clavicle
how does rotation occur (SC)
w/ elevation of the arm and w/ scapular rotation
what is upward rotation (SC)
anterior edge of the clavicle moving upwards
also called posterior rotation
what is downward rotation
anterior edge of the clavicle moving downwards
also called anterior rotation
how much upward rotation can the clavicle do (SC joint)
30-45 degrees
how much downward rotation can the clavicle do (SC joint)
10 degrees
elevation arthrokinematics (SC joint)
a convex clavicle moving on a concave manubrium
the bone motion and roll are in the same direction (up)
glide is in the opposite direction (down)
depression arthrokinematics (SC joint)
a convex clavicle moving on a concave manubrium
the bone motion and roll are in the same direction (down)
glide is in the opposite direction (up)
protraction arthrokinematics (SC joint)
a concave clavicle moving on a convex manubrium
bone motion, roll and glide are in the same direction anteriorly
retraction arthrokinematics (SC joint)
a concave clavicle moving on a convex manubrium
bone motion, roll and glide are in the same direction posteriorly
rotation arthrokinematics (SC joint)
primarily a spin motion
3 ligaments of the SC joint
anterior & posterior sternoclavicular ligaments
interclavicular ligament
costoclavicular ligament
anterior and posterior sternoclavicular ligaments
reinforce the joint capsule
interclavicular ligament
runs b/w the 2 clavicles
costoclavicular ligament
runs from the first rib to the clavicle
function of the ligaments during protraction
limited by costoclavicular ligament, posterior sternoclavicular capsule and ligament and posterior fibers of interclavicular ligament
movement of protraction is anterior, so limitation is posterior
function of the ligaments during retraction
limited by anterior fibers of costoclavicular ligament, anterior sternoclavicular capsule and ligament
movement is posterior so thinks that limit it will be anterior
function of the ligaments during elevation
limited by tension in the costoclavicular ligament, anterior sternoclavicular capsule and ligament
movement is upwards, limited by inferior factors
function of ligaments during depression
limited by interclavicular ligament and the superior capsule
movement is downwards, limited by superior factors
what is the AC joint
the articulation b/w the acromial end of the clavicle and the scapula
very incongruent
what type of joint is the AC joint
plane synovial joint
how many degrees of freedom does the AC joint have
3
articular surface shape of the AC joint
will vary
usually a convex/flattened distal clavicle and a concave acromion