Shoulder joint

INTRODUCTION:
  • Enarthrodial or Ball-and-Socket joint
  • Bones Involve:-
  • Large globular head of humerus
  • Glenoid cavity of scapula
  • Protected against displacement by tendons and by atmospheric pressure.
  • Musculotendinous Cuff of the Shoulder or Rotator Cuff
  • Fibrous sheath formed by four flattened tendons, blend with capsule strengthen & stabilizes joint.
  • The muscles which form the cuff arise from the scapula and are inserted into the lesser and greater tubercles of humerus.
  • It is also known as dynamic stabiliser of shoulder joint.
  • Muscles of rotator cuff.
  1. Subscapularis
  2. Supraspinatus
  3. Infraspinatus
  4. Teres minor
  • Ligaments around gleno-humeral joint Limit the amount of joint movement
  1. Capsular
  2. Coracohumeral
  3. Transverse Humeral
  4. Glenoid Ligament
  • From Above protected by arched vault formed by:
  1. Under surface of coracoid process
  2. Under surface of acromion process
  3. Coraco-acromial ligament
  • The inferior part of shoulder joint capsule is the weakest area of shoulder joint capsule
GLENOID CAVITY:
  • Pear Shape
  • Shallow
  • Directed Laterally and Upward
  • Only1/3rd of the humeral head comes in contact with the glenoid cavity at any position.
  • Glenoid Fossa is deepened by a fibro-cartilaginous rim of Glenoid labrum.
  • It is the articulating surface of shoulder joint that lies in scapula.
LIGAMENTS SURROUNDING SHOULDER JOINT:
  • CAPSULAR LIGAMENT 
  • GLENOHUMERAL LIGAMENT
  • CORACO-HUMERAL LIGAMENT
  • TRANSVERSE HUMERAL LIGAMENTS
  • GLENOID LABRUM
  • SYNOVIAL MEMBRANE
BURSAE IN RELATION TO THE SHOULDER JOINT:-
  • SUBSCAPULAR BURSA
  • INFRASPINATUS BURSA
  • SUBACROMIAL BURSA (SUBDELTOID)
  • SUBCORACOID BURSA
MUSCLES ACTING ON SHOULDER JOINT:-
  • Above - Supraspinatus
  • Below - Long head of Triceps
  • Front - Subscapularis
  • Behind - Infraspinatus and Teres Minor 
  • Deltoid is placed most externally and covers the articulation from its outer side, as well as in front and behind.
  • Long head of the biceps muscle crosses through the shoulder joint( The tendon of the long head of biceps brachii muscle passes superiorly through the joint and restricts upward movement of humeral head on glenoid cavity).
BLOOD & NERVE SUPPLY:-
  • Blood Supplyv Anterior circumflex humeral vessels
  1. Posterior circumflex humeral vessels
  2. Suprascapular vessels
  • Nerve Supply
  1. Axillary nerve
  2. Musculocutaneous nerve
  3. Suprascapular Nerve
  4. Lateral pectoral nerve
CLOSE & LOOSE PACKED POSITION:-
  • Close Packed position
  1. Position where the articular surfaces of joint are in maximal congruency status, resulting in greatest mechanical stability.
  2. Most ligament and capsule surrounding joint are taut.
  3. 90° of glenohumeral abduction and full external rotation
  • Loose Packed position
  1. Position where the articular surface of joint are in minimal congruency status.
  2. Supporting structures are most lax.
  3. 55° of semi-abduction and 30° of horizontal adduction
Exam Question
  • The inferior part of shoulder joint capsule is the weakest area of shoulder joint capsule
  • Long head of the biceps muscle crosses through the shoulder joint
  • The tendon of the long head of biceps brachii muscle passes superiorly through the joint and restricts upward movement of humeral head on glenoid cavity.
  • Rotator cuff is called the dynamic stabiliser of the shoulder joint

Don't Forget to Solve all the previous Year Question asked on Shoulder joint