shoulder joint

Muscles acting at shoulder joint

Flexion	§  Clavicular head of pectoralis major    §  Anterior fibres of deltoid    §  Coracobrachialis
Extension	§  Posterior fibres of deltoid    §  Teres major    §  Lattisimus dorsii
Abduction	§  Supraspinatous    §  Deltoid
Adduction	§  Pectoralis major    §  Teres major    §  Lattisimus dorsi
Medial rotation	§  Pectoralis major    §  Teres major    §  Latissimus dorsi    §  Subscapularis
Lateral rotation	§  Infraspinatus    §  Teres minor    §  Posterior fibres of deltoid

Movements during shoulder abduction

o   Lateral rotation of scapula

o   Elevation of humerus

o   Movements at clavicular end of sterno-clavicular joint

o   Axial rotation of humerus at acromioclavicular joint

o   For every 3^o abduction, 2^o abduction occurs in shoulder joint ,1^o abduction occurs by lateral/forward  rotation of scapula

o   Abduction is initiated by supra spinatus but main abductor is deltoid

Shoulder abduction

For every 15^O of abduction,  shoulder joint contributes 10^O but girdle contributes 5^O(in the ratio of 2:1)

After 90^O abduction,this ratio is reversed

Supraspinatus –initiates abduction of shoulder  & assisted by middle fibres of deltoid

First 90-120  degrees of shoulder abduction takes place at ----------- glenohumeral joint

After this fixation is NOT d/t  bony interlocking b/w greater tuberosity and acromion d/t no further articular surface  available on humerus

Abduction of shoulder > 90  degree requires --------------- rotation of scapula(achieved by contraction of trapezius & serratus anterior)

Stages of shoulder abduction--------

§  Stages I –initial 15 to 30^O --------supraspinatous

§  Stage II—30 to  90-120^O----------deltoid (acromial fibres)

§  Stage III(Hyperabduction)—90-120 to 180^O------- trapezius,serratus anterior

From 120-150^O----------- infraspinatus is more active than supraspinatous