1. Ch. 21 Shoulder

2. Objectives
Name the three articulations that constitute the shoulder girdle complex.
Describe how stability of the shoulder is maintained.
Recite the names of the four muscles that come together to form the rotator cuff.
Explain the anatomy of the shoulder complex.
Identify major injuries and conditions of the shoulder.

3. Anatomy Ball and socket joint most mobile joint in the body Humerus
Clavicle- collar bone
Scapula- shoulder blade
Acromion process
Coracoid process

6. Joints and Movements Flexion Extension Abduction Adduction
Internal Rotation
External Roation
Elevation/Depression
Protraction/Retraction
Glenohumeral Joint- the actual shoulder joint
Acromioclavicular Joint
Sternoclavicular Joint
Scapulothoracic Joint

7. Shoulder Flexion Pectoralis Major Coracobrachialis Biceps brachii
anterior fibers of deltoid

8. Shoulder Extension latissimus dorsi teres major long head of triceps
posterior fibers of the deltoid

9. Shoulder Abduction
True abduction: supraspinatus (first 15 degrees), deltoid
Upward rotation: trapezius, serratus anterior
True abduction from arm to side to parallel with the ground

10. Shoulder Adduction
Downward rotation: pectoralis minor, pectoralis major, latissimus dorsi
True Adduction: same as downward rotation with addition of teres major and the lowest fibers of the deltoid

11. Internal Rotation Subscapularis Latissimus dorsi Teres major
Pectoralis major
Anterior fibers of deltoid

12. External Rotation Infraspinatus Teres minor
Posterior fibers of deltoid

13. Elevation/Depression
pectoralis minor
lower fibers of the trapezius
subclavius
latissimus dorsi
Elevation
levator scapulae
the upper fibers of the trapezius

14. Protraction/Retraction
rhomboid major and minor
trapezius
Protraction
serratus anterior
pectoralis minor and major

15. Rotator Cuff
Supraspinatus
Infraspinatus
Teres Minor
Subscapularis

16. Muscle Force Couple
Two equal forces acting in opposite directions to rotate a part around its axis
During shoulder abduction, the rotator cuff is pulling down on the humeral head while the deltoid is lifting the arm.

17. Muscle Weakness
Most athletes have strong anterior shoulder muscles but weak posterior shoulder muscles
This imbalance causes forward shoulder and other shoulder injuries
Mirror muscles