Anatomical Kinesiology - Upper Extremity

open mechanical system

• right and left sides are not directly attached

• can move independently

  • ex: shoulder girdle

shoulder girdle articulation

• sternoclavicular

• acromioclavicular

• coracoclavicular

• scapulothoracic

shoulder girdle bones

• scapula and clavicle

  • move as a unit

  • clavicle articulation with sternum is the only bony link to axial skeleton

roles of clavicle

• helps facilitate scapular motion

• site of muscular attachment

• provides barrier to protect underlying structures

• acts as a strut to stabilize shoulder and prevent medial displacement when muscles contract

• prevents an inferior migration of shoulder girdle

function of scapula

primarily to provide muscle attachment sites for shoulder muscles

key bony landmarks of scapula (shoulder girdle)

• glenoid fossa

• coracoid process

• acromion process

• lateral border

• medial border

• inferior angle

• superior angle

• spine of scapula

sternoclavicular (SC) articulation

• articulation between sternum and clavicle

  • ball and socket joint

  • freely mobile in frontal and transverse plane

  • limited sagittal movement

• site of most movement of shoulder girdle

  • elevation:depression (60º)

  • protraction:retraction (30º)

  • anterior:posterior (30-45º)

sternoclavicular (SC) articulation ligamentous support

• anterior sternoclavicular ligament

• posterior sternoclavicular ligament

• costoclavicular ligament

• interclavicular ligament

acromioclavicular (AC) articulation

• articulation between acromion process and distal end of clavicle

• motion most noticeable during arm elevation (shoulder abduction)

• joint handles large contact stresses as a result of high axial loads transmitted through the joint

• weak bony support

acromioclavicular (AC) articulation ligamentous support

• superior acromioclavicular ligament

• inferior acromioclavicular ligament

• coracoacromial ligament

coracoclavicular (CC) articulation

• articulation between coracoid process of scapula and clavicle

• assists in reinforcement of the weak AC articulation

• weak non-existent bony support

coracoclavicular (CC) articulation ligamentous support

• coracoclavicular ligaments

  • conoid and trapezoid

scapulothoracic articulation

• articulation between anterior surface of the scapula (scapular fossa) and thoracic wall

• acts to stabilize shoulder region during lifting (shrugging, picking up a suitcase)

• facilitates overhead movements through elevation and upward rotation of glenohumeral joint

• supported dynamically by muscles

  • no ligament support

shoulder girdle movements

• shoulder girdle movements = scapula movements

• protraction (abduction)

• retraction (adduction)

• downward rotation

• upward rotation

• depression

• elevation

scapular protraction

• abduction

• scapula moves laterally away from spinal column

scapular retraction

• adduction

• scapula moves medially toward spinal column

downward rotation

returning inferior angle inferomedially toward spinal column and glenoid fossa to normal position

upward rotation

turning glenoid fossa upward and moving inferior angle superolaterally away from spinal column

depression

• downward or inferior movement

• returning to normal position

elevation

• upward or superior movement

• shrugging shoulders

function of shoulder girdle muscles

• stabilize scapula

  • maintain scapula in relatively static position during shoulder joint actions

  • provide stable base for shoulder muscles to move

• move shoulder girdle

• enhance movement of upper extremity when shoulder goes through extreme ranges of motion

scapulohumeral rhythm and effects

• synergy with muscles of glenohumeral joint

  • at extreme ranges of motion muscles move shoulder girdle to position glenoid fossa and allows humerus more mobility

  • without accompany scapula movement humerus can only be raised approximately 90º of total shoulder abduction and flexion

  • synergy between scapula and shoulder joint muscles enhances movement of entire upper extremity

• scapular rotation to facilitate shoulder abduction

  • 1st 30º of abduction

    • little scapular rotation

    • shoulder: 30º, scapula: 6º

  • beyond 30º

    • for every 2º of shoulder movement scapular rotates 1º, 2:1

shoulder girdle muscles information

• 5 primary muscles

  • originate on axial skeleton and insert on scapula and/or clavicle

  • do not attach to humerus and do not cause shoulder joint actions

  • essential in providing dynamic stability of scapula so it can serve as base of support for shoulder joint activities

shoulder girdle muscles

• levator scapulae

• trapezius

• rhomboids

• serratus anterior

• pectoralis minor

trapezius muscle movements

• upper fibers (primary)

  • elevation & upward rotation

• middle fibers (primary)

  • elevation & retraction

• lower fibers (primary)

  • depression, upward rotation, & retraction

levator scapulae muscle movements

• elevation (primary)

• downward rotation

rhomboid (major and minor) muscles movement

• retraction (primary)

• elevation

• downward rotation

serratus anterior muscle movements

• protraction (primary)

• upward rotation (primary)

pectoralis minor muscle movements

• depression (primary)

• protraction (primary)

• downward rotation

subclavius muscle movements

• stabilization and protection of SC joint (primary)

• depression

• protraction

scapular protraction (abduction) muscles

• agonists

  • pectoralis minor

  • serratus anterior

scapular retraction (adduction) muscles

• agonist

  • middle trapezius

  • rhomboids

scapular upward rotation muscles

• agonist

  • middle trapezius

  • lower trapezius

  • serratus anterior

scapular downward rotation muscles

• agonists

  • pectoralis minor

  • rhomboid

scapular elevation muscles

• agonists

  • rhomboids

  • levator scapulae

  • upper trapezius

scapular depression muscles

• agonists

  • lower trapezius muscles

  • pectoralis minor

glenohumeral (GH) articulation

• articulation of humerus and glenoid fossa

• designed for mobility, most mobile in body

• lack bony and ligamentous support

• shallow glenoid fossa

• half-spherical humeral head

shoulder joint information

• wide range of motion of the shoulder joint in many different planes requiring a significant amount of laxity

• common to have instability problems

  • rotator cuff impingement

  • subluxations and dislocation

• price of mobility is reduced stability

  • more mobile a joint is the less stable it is

  • more stable a joint is the less mobile it is

shoulder joint and scapula movements

• scapular movement usually occurs with movement of humerus

  • humeral flexion and abduction:scapular elevation, upward rotation, and abduction

  • humeral adduction and extension:scapular depression, downward rotation, and adduction

  • humeral internal rotation and horizontal adduction:scapular abduction

  • humeral external rotation and horizontal abduction:scapular adduction

scapula key bony landmarks (shoulder joint)

• supraspinatus fossa

• infraspinatus fossa

• subscapular fossa

• spine of the scapula

• glenoid fossa

• coracoid fossa

• acromion process

• inferior angle

proximal humerus key bony landmarks

• humeral head

• greater tubercle

• lesser tubercle

• intertubercular groove

• deltoid tuberosity

bone attachments of shoulder joint

• scapula, clavicle, and humerus

  • serve as attachments for shoulder joint muscles

stability of glenohumeral joint

• fully sealed which provides suction and resists a dislocation force at lower loads

• passive, static stabilizers

  • articular surface, glenoid labrum, joint capsule, and ligaments

• dynamic support

  • occurs mostly at midrange of motion and provided by muscles as they contract in coordinated pattern to compress humeral head in glenoid cavity

• posterior stability

  • posterior rotator cuff muscles

• anterior stability

  • subscapularis

  • long head of biceps (superior humeral head translation)

• deltoid and other scapulothoracic muscle position the scapula to provide maximum GH stability