1. ESS 303 – Biomechanics
Shoulder Joint

2. The Scapula (Right)

3. Humerus (Right)
Anterior View Posterior View

5. The Shoulder Joint Shallow ball-and-socket
Socket: Glenoid fossa of the shoulder blade
Ball: ½ the spherical head of the humerus
No more than ½ of the head is in the socket at any given time
Bony stability is weak
In fact – the head may move up to 2-3 cm away from the glenoid fossa

6. Stability Keeping the humoral head in contact with the glenoid fossa
Passive: Glenoid Labrum
Circles around the outside of the glenoid cavity
Increases depth of concavity
Active: Rotator cuff

7. Rotator Cuff
Muscles tense to stabilize the humoral head against the glenoid fossa
Helps prevent the head from rotating out of the fossa
Allows the deltoid to contribute to abduction
4 muscles: supraspinatus, subscapularis, infraspinatus, and teres minor

9. Rotator Cuff Injuries: Common
Types: Tendonitis, bursitis, strain or tear
Who: Baseball pitchers & anyone who puts heavy demands on their shoulders
Most treated with simple care and exercise
Causes: age (>40), poor posture, breaking a fall with your arm, heavy lifting (especially overhead), repetitive stress, others

10. Rotator Cuff Injuries: Common

11. Rotator Cuff Injuries: Common
Self treatment:
Stop the activity – for a few days or until pain stops
Ice and heat
Medications
Exercises
Medical treatment
Severe or long-lasting (> 1 week) pain, immobile, etc
Medications, surgery, etc

12. Dislocation & Subluxation

14. Movements & Major Muscles
Flexion: pectoralis major (clavicular), anterior deltoid & coracobrcahialis
Extension: pectoralis major (sternal), latissimus dorsi & teres major
Abduction: middle deltoid & supraspinatus
Adduction: pectoralis major (sternal), latissimus dorsi & teres major

15. Movements & Major Muscles
Horizontal (Transverse) Abduction: middle and posterior deltoids, infraspinatus & teres minor
Horizontal (Transverse) Adduction: pectoralis major, anterior deltoid, coracobrachialis
Medial Rotation: pectoralis major, latissimus dorsi, teres major & subscapularis
Lateral Rotation: teres minor, infraspinatus & posterior deltoid
Other movements are exaggerations or combinations of above: Hyperextension, Hyperabduction, Hyperadduction & Circumduction