lecture 6: shoulder function Flashcards
Function of the shoulder griddle
-the shoulder griddle is the attachment point of the upper limb to the axil skeleton
-very mobile so that we can do a variety of tasks
-synergy between the scapular joint and shoulder joint for throwing and reaching
movements of the shoulder complex take place around
sternoclaivular joint
acromioclavicular joint
glenohumeral joint
scapulothoracic joint
sternoclavicular joint: ligaments
interclavicular ligament- limits superior and lateral displacement of clavicle
costcoclavicular ligament- main support limits all ROM except depression
sternoclavicular ligament (ant & post)- limits anterior and posterior gridle of clavicle
acromioclavicular joint: ligamnets
acromioclavicualr ligament- limits superior motion. prevents the clavicle from being driven under the acromion
coracoclavicular ligament: provides strength to AC joint and provides means by which scapula and limb can suspend from the clavicle
glenohumeral joint function
articulation formed between the large head of the humerus and the shallow socket of the glenoid fossa
the glenoid labrum
increases contact area with humeral head and therefore helps to stabilize this very movable joint
glenoidhumeral ligments (4)
-superior glenohumeral ligament
anterior displacement of humeral head
some posterior translation
inferior translation
-middle glenohumeral liagment anterior displacement of humera head
external rotation
-inferior glenohumeral ligament
anterior displacement of humeral head
some posterior translation
inferior translation
-coracohumeral ligament
resists inferior and posterior translation
humeral head position
changes in either position of the humeral head or position of the glenoid fossa can significantly impact function of the shoulder and increase the risk of injury
humeral head position can be altered by:
-muscle imbalances
weak muscles
tight structures
posture
-instability
ligament laxity
injury
-loss of neural control
impacting dynamic stability
dynamic stabilizers of glenohumeral joint
the passive restraints of the glenohumeral joint still allow for significant mobility, which makes it unstable
the dynamic stabilizers must compensate to help hold the humeral head in the glenoid fossa
the rotator cuff muscles provide this dynamic stability
internal vs external rotators
internal rotators of the shoulder are able to produce more force comapred to the external rotators of the shoulder
due to the greater cross sectional area of the internal rotators
their ability to generate more force is useful in high-speed throwing
scapulothoracic joint function
not a true joint but rather a point of contact between the posterior-lateral wall of the thorax. the shoulder gridle muscles are essendtial in providing stability so that the shoulder joint will have a stable base for movement
scapulohumeral rhythm
shoulder abduction
typically 180 degrees
includes combined movement at the 60~scapulothoratic and 120~glenohumeral degrees
2:1 ratio
for every 2 degrees of motion that occurs at the glenohumeral joint, 1 degree occurs at the scapulothoracic joint
glenoid fossa position
glenoid fossa position can be altered bu:
-muscle imbalances
weak muscles
tight structures
postuire
-instability
ligament laxity
injury
-loss of neural control
impacting dynamic stability
upward rotation of the scapula
upward rotation of the scapula:
upper fibers of the trapezius
lower fibers of the tapezius
serratus anterior
passive restratint: ligaments
sternoclavicular ligaments
acromioclavicular ligaments
glenohumeral ligaments
limiting structures- flexion/ extension
flexion
posterior part of coracohumeral lig, trapezoid lig, posterior part of joint capsule
muscles= rhomboids, lavator scapulae, infraspinatus, teres minor, triceps, ;atissimus dorsi, posterior deltoid, teres major
extension
Anterior part of coracohumeral
lig
Anterior part of joint capsule GHjt
All parts of the glenohumeral
joint ligaments
Pectoralis Major
Biceps Brachii
Anterior Deltoid
Coracobrachialis
limiting structures- abduction/ adduction
ligaments-
Middle & Inferior glenohumeral
lig
Trapezoid Lig
Inferior part of capsule of GHjt
Inferior glenohumeral ligament
muscles
Rhomboids
Levator scapulae
Coracobrachialis
Pectoralis Major
Latissimus Dorsi
Teres Major
Subscapularis
adduction- body prevents adduction
limititng structures- medial/ lateral rotation
medial (internal) rotation-
ligaments
posterior glenohumeral joint capsule
muscles
infraspinatus, teres minor
lateral (external) rotation
ligaments
anterior glenohumeral joint caosule glenohumeral ligaments (espically middle portion)
coracohumeral ligaments
muscles
pectoralis major
latissimus dorsi
teres major
subscapularis
active restraints: muscles
subscapularis
-medially rotates and adducts the arm. helps to hold the head of the humers in the glenoid cavity
teres minor
-latteral rotates the arm and helps to hold the humeral head in the glenoid cavity of the scapula
infraspinatus
supraspinatus
-initiates and assists deltoid in abduction and acts with other rotator cuff muscles
muscles of the shoulder and their action
upper fibers trapezius
-elevates the scapula
rhomboids
-retracts scapula and rotates it to depress
levator scapula
-elevates scapula and assists with downward rotation of the scapula. can also act on the cervical spine
lower fibers scapula
-depresses and retracts
pectoralis minor
-stabilizers the scapula by drawing it inferiorly and interiorly against thoracic wall
latissimus dorsi
-extends,adducts and medially rotates humerus; raises body toward arms during climbling
subclavius
-anchors and depresses the scapula
subclavius anterior
-protarcts the scapula and holds it against the thoracic wall; rotates the scapula in an upward direction
pectoralis major
adducts ans medially rotates the humerus; draws the scapula anteriorly and inferiorly. acting alone the clavicular head flexes the humerus, and the sternocostal head will extend the humerus from a flexed position
middle fibers trapezius
-retracts the scapula
muscles of the shoulder
deltoid
abduction, flexion of the shoulder
biceps brachii
supinates forearm and flexes the elbow. short head resists dislocation of the shoulder
coracobrachialis
-flexes and adducts the shoulder joint
triceps brachii
Primary extensor of the elbow joint. Long head extends shoulder and resists dislocation of the shoulder, especially during adduction.
teres major
adduction at the shoulder joint, medial rotation of the
shoulder joint. Extend the shoulder from a flexed
position.
shoulder conditions
instability.
glenoid labrum injury
dislocation and subluxation
impingements or tendinopathy
scapular control (muscular imbalance, innervation)
humeral head position (muscular imbalance)
instability: dislocation
anterior dislocation
most common traumatic sports injury
arm is forced into excessive abduction and external rotation
instability:dislocation
anterior dislocation can result in:
damage to glenoid labrums attachment to anterior glenoid margin
ligament damage
damage to axillary nerve
imparied sensation on lateral side of arm
impairment of teres minor& deltoid
instability: labral tear
glenoid labrum
-serves as an attachment site for shoulder capsule, glenohumeral ligament and biceps tendon
commonly injured due to repetitive overhead throwing or trauma
impingement: glenoid position
poot scapular control when performung arm movements inadequate movement of scapula
when the glenoidhumeral joint when there is inadequate movement of the scapula= tendonopathy= small tears
scapular control: innervention
long thoratic nerve
innervates serratus anterior
damaged by traction on neck or shoulder or by blunt tramuma causes paralysis of serratus anterior
impingement: muscle imbalances
imbalances between muscles that support the humeral head
rotator cuff msucles
external rotators vs internal rotators
tendinopathy
tendons become inflamed due to overuse
or from repetitve impingement
biceps rupture
supraspinatus rupture
most commonly injuired rotator cuff muscle
shoulder conditions
- muscle imbalances
- inferior movement of acromion
=decreased subacromial space> impingement with exercise> rotator cuff tendinopathy (overuse, instability)> swelling of rotator cuff tendon
