the shoulder complex Flashcards
4 joints of the shoulder complex
glenohumeral joint
sternoclavicular joint
acromioclavicular joint
scapulothoracic joint
how much shoulder ROM is contributed by the glenohumeral joint
2/3s
how much shoulder ROM is contributed by the scapulothoracic joint
1/3
upper thoracic rotation occurs ___(ipsi/contra)__ with shoulder elevation
ipsilateral
how many degrees of freedom occur at the SC joint (& what are they)?
3 DoF
elevation/depression
pro/retraction
anterior/posterior
where is the superior SC joint articulation
medial clavicle and disc
where is the inferior SC joint articulation
medial clavicle with manubrium and first costal cartilage
what are the 2 jobs of the SC joint disc
increase congruence
absorbs force
arthrokinematics of elevation/depression of SC joint
clavicle rolls and glides on disc
arthrokinematics of protraction/retraction of SC joint
sc disc + clavicle roll and slide on manubrium
costoclavicular ligament limits what motion (+ counteracts which 2 muscles)
limits elevation of lateral clavicle by counteracting SCM and sternohyoid muscles
what direction does the anterior and posterior fibers of the costoclavicular ligament run?
anterior: laterally
posterior: medially
interclavicular ligament
resists excessive depression of clavicle + superior gliding of clavicle on manubrium
what degree of ROM can SC joint elevate + depress?
48* elevation
15* depression
what degree of ROM can SC joint protraction/retraction?
15-20* pro
30* retraction
what degree of ROM can SC joint posteriorly + anteriorly rotate?
50* post
10* ant
how does the clavicle move in elevation (lat vs med ends)
lateral end moves up
medial end rolls superiorly + slides inferiorly on sternum
what type of synovial joint is the SC joint
saddle
how does the clavicle move in depression (lat vs med ends)
lateral end moves down
medial end rolls inferiorly + slides superiorly on sternum
how does the clavicle move in protraction (lat vs med ends)
lateral end moves anteriorly (transverse plane)
medial end rolls and slides anteriorly on sternum
how does the clavicle move in retraction (lat vs med ends)
lateral end moves posteriorly
medial end rolls and slides posteriorly on sternum
t/f: SC joint is commonly susceptible to degenerative changes
FALSE –> the AC joint is
how many degrees of freedom does the AC joint have (+ what movements)
3 DoF
what joint allows the scapula to rotate during arm movements
the AC joint!!
what joint maximized the scapula’s contact to the thorax
AC joint
what are the 3 possible orientations of the AC joint?
which orientation is most susceptible to degeneration? which is most common?
mediolateral (most common)
lateromedial
vertical <– most susceptible to shear forces
coracoclavicular ligament
firmly unites clavicle and scapula
conoid ligament
resists inferior forces
trapezoid ligament
resists posterior translation
couple ________ clavicle rotation and scapula _________ rotation during arm elevation
posterior
upward
how many degrees of internal and external rotation does the AC joint have?
which axis does it rotate around?
20-35*
vertical axis
how many degrees of anterior and posterior tilting does the AC joint have?
which axis does it tilt around?
20-40*
oblique coronal axis
how many degrees of upward and downward rotation does the AC joint have?
which axis does it rotate around?
up: 30*
down: 17*
oblique AP axis
how does the glenoid fossa move when the AC joint rotates up and down?
tilts the glenoid fossa up and down
2 most common MOIs of AC joint
contact sport collision
falls on shoulder with arm ADducted
the scapulothoracic “joint” depends on the integrity and structure of which 2 joints?
SC and AC joints
where does the scapula rest in relation the the rib cage and the midline
2” away from midline
on ribs 2-7
___ degrees of upward rotation is required for arm elevation
60
excessive internal rotation of the ST joint leads to….
scapular winging
how does the scapula move in shoulder flexion/abduction (3)
protraction
elevation
upward rotation
how does the SC joint move in shoulder flexion/abduction? (3)
- protraction (rolls + slides anteriorly)
- posterior rotation (inferior slide, superior roll @ disk)
- elevation
how does the SC joint move in shoulder lowering/adduction? (3)
- retraction (post roll, post glide)
- depression
- anterior rotation (sup slide, inf roll at disc)
how does the scapula move in shoulder lowering/adduction (3)
retraction
depression
downward rotation
how does the AC joint move in shoulder flexion/abduction (1)
upward rotation
how does the AC joint move in shoulder lowering/adduction (1)
downward rotation
what joint is the “premier example” of dynamic stabilization
ST joint
t/f: the humeral head is larger than the glenoid fossa
true
what is the angle of inclination range of the humeral head + shaft of humerus
130-150*
what is the angle of torsion in GH joint
30*
what % does the glenoid labrum increase glenoid fossa concavity
~50%
GH capsule is most susceptible to which direction of dislocation?
anterior!
superior GH ligament
resists anterior and inferior translations of humeral head (at 0* abduction)
middle GH ligament
prevents ANY translations of humeral head from 0-60* degrees abduction
interior GH ligament complex has 3 components: what are they and what motions do they resist?
anterior = prevents ant/inf translation (ABD/IR)
posterior = prevents post/inf translation (ABD/IR)
axillary pouch = prevents inf translation (ABD)
coracohumeral ligament
forms a tunnel for LH of biceps to pass through
where are the 2 bands of the coracohumeral ligament
first band: base of coracoid to edge of supraspinatus tendon + greater tubercle
second band: base of coracoid into subscapularis and lesser tubercle
3 structures that form a “vault” over the humeral head
coracoid
acromion
coracoacromial ligament
subacromial space contains (3 main structures)
subacromial bursa
rotator cuff tendons
tendon of LHB
flexion + extension ROM of GH joint
120* flex
50* ext
ab/adduction ROM of GH joint
90-120*
what movement of the arm is required for full range abduction?
lateral rotation
in elevation, how does the GH slide and roll
humeral head slides inferiorly + rolls superiorly
which rotator cuff muscle is key in static stabilization of GH joint
supraspinatus
if supraspinatus is not turning on, what direction is the shoulder more susceptible to dislocate
inferiorly
what muscle is the prime mover for GH abduction
deltoid
deltoid requires synergistic help from which muscle group to rotate humeral head
rotator cuff
what muscle contributes for the first part of shoulder abduction
supraspinatus
what is SITS
supraspinatus
infraspinatus
teres minor
subscapularis
which 2 rotator cuff muscles help with lateral rotation to clear the greater tub during UE elevation
infraspinatus
teres minor
which muscle centers the head of the humerus and reduces vertical + anterior shear?
long head of biceps brachii
which ROM do the greatest shear forces occur?
between 30-60* elevation
which tendon in the GH joint is the most vulnerable to injury
supraspinatus
(can tear or be impinged)
what age group is most susceptible to RCTs
60+ years
what ROM degree range causes the most pain in a person with a RCT
60-120*
scapulohumeral rhythm ST vs GH ROM
ST = 60*
GH = 120*
scapulohumeral motion distributes motion between how many joints
4
t/f: scapulohumeral motion prevents active insufficiency as the scapula rotates up
true!! it helps maintain good length-tension of humeral muscles
how does the GH joint move in shoulder flexion/abduction
superior roll of humerus with inferior slide on glenoid
how does the GH joint move in shoulder lowering/adduction
inferior roll of humerus with superior slide on glenoid
what is the overall ratio of movement with GH:ST
2:1 GH:ST
what ROMs of scapulohumeral rhythm is primarily GH joint
0-60*
120-180*
what part of ROM in scapulohumeral rhythm is ST:GH 1:1
60-120*
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what muscles act as force couple to allow ST upward rotation
upper/lower trap + serratus anterior
which deltoid muscles work together for abduction of shoulder
anterior and middle delt
which part of the delt adds joint compression
posterior delt
length-tension depends on which joint’s motions
ST joint
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