Shoulder Joint

Question 1

Articulating surfaces

Answer 1

Head of the humerus

Glenoid cavity of scapula

Question 2

Joint capsule and bursae

Answer 2

Fibrous sheath which encloses structures of joint
Extends from anatomical neck of humerus to the border of the glenoid fossa
Capsule lax permitting movement
Synovial membrane prevents friction
- Subacromial bursa - inferiorly to deltoid and acromion, superiorly to supraspinatus tendon and joint capsule - inflammation of this causes several shoulder problems
- Subscapular bursa - between subscapularis tendon and scapula - reduces wear and tear on tendon during movement

Question 3

Ligaments

Answer 3

• Glenohumeral ligaments (superior, middle, inferior) - 3 bands, runs with joint capsule from glenoid fossa to anatomical neck of humerus, stabilise anterior aspect of joint
• Coracohumeral ligament - attaches to base of coracoid process to greater tubercle of humerus, supports superior part of joint capsule
• Transverse humeral ligament - spans distance between tubercles of humerus, holds tendon of long head of biceps in intertubecular groove

Question 4

Neurovascular supply

Answer 4

Anterior and posterior circumflex humeral arteries
Suprascapular artery
Axillary, suprascapular and lateral pectoral nerves (C5/6)

Question 5

Movements

Answer 5

Extension - posterior deltoid, latissimus dorsi, teres major
Flexion - biceps brachii, pec. major, anterior deltoid, coracobrachialis
Abduction - 0-15 - supraspinatus / 15-90 - middle fibres of deltoid / 90+ - trapezius and serratus anterior
Adduction - contraction pec. major, latissimus dorsi, teres major
Medial rotation - contraction subscapularis, pec. major, latissimus dorsi, teres major, anterior deltoid
Lateral rotation - contraction infraspinatus, teres minor

Question 6

Mobility and stability

Answer 6

• Mobility - ball and socket joint / shallow glenoid cavity, large humeral head, 1:4 disproportion in surfaces / lax joint capsule
• Stability - rotator cuff muscles pull head into cavity / glenoid labrum, ridge surrounding cavity deepening it, reduces dislocation risk / ligaments form coraco-acromial arch and reinforce joint capsule

Question 7

Dislocation

Answer 7

• Anterior - excessive extension and lateral rotation of humerus, head forced anteriorly and inferiorly -> weakest part of capsule, tearing of capsule -> inc. risk future dislocations
  Axillary nerve at risk -> paralysis of deltoid, loss of sensation over regimental badge area
  Can also stretch radial nerve (tightly bound in radial groove)

Question 8

Rotator cuff tendonitis

Answer 8

Often under heavy strain so injury common
Inflammation of muscle tendons (overuse)
Over time - degenerative changes in subacromial bursa and supraspinatus tendon -> increases friction between structures of joint
Sign - painful arc (pain when the affected area comes into contact with the acromion)