A joint articulation or articulate surface is the

A joint, articulation (or articulate surface) is the location at which bones connect

Shoulder joint

multiaxial synovial ball and socket joint

Shoulder joint q Glenoid labrum

q Capsule

q Ligaments 1. The glenohumeral ligaments 2. The transverse humeral ligament 3. The coracohumeral ligament 4. The coracoacromial ligament (accessory ligament)

Synovial membrane (also known as synovium or stratum synoviale) is the soft tissue found between the articular capsule (joint capsule) and the joint cavity of synovial joints

A bursa (plural bursae) is a small fluid-filled sac lined by synovial membrane with an inner capillary layer of viscous fluid (similar in consistency to that of a raw egg white). It provides a cushion between bones and tendons and/or muscles around a joint. This helps to reduce friction between the bones and allows free movement. Bursae are filled with synovial fluid and are found around most major joints of the body.

q Synovial membrane 1. Subacromial bursa 2. Subscapularis bursa

q Factors contributing to stability of shoulder joint

q Shoulder joint & its relations

Nerve Supply

Joint Nerve Supply Sternoclavicular Supraclavicular N Nerve to subclavius Acromioclavicular Suprascapular N Glenohumeral Axillary N Suprascapular N Proximal radioulnar Branches of median, ulnar, radial & musculocutaneous N Distal radioulnar Ant interosseus & deep branch of radial N

Rotator Cuff • Tendinous band formed by the insertions of: – – Supraspinatus (D) Infraspinatus (E) Teres minor (F) Subscapularis

Rotator Cuff (cont’d) • These muscles help keep the head of the humerus “rotating” against the glenoid fossa during joint motion

Shoulder Stability • Shoulder joint allows a great deal of motion • Unstable joint • Many anatomical structures contribute to the stability of the shoulder

Shoulder Stability (cont’d) • Glenoid labrum • Glenoid fossa anterior, lateral and upward direction – Upward direction provides some stability • Joint capsule reinforced by the coracohumeral and glenohumeral ligaments • Capsule completely surrounds fossa, partial vacuum • Rotator cuff muscles • Shoulder muscles

Movements

Shoulder joint q Principal muscles responsible for movements at shoulder joint are: 1. Deltoid 2. Pectoralis major 3. Latissimus dorsi 4. Teres major q The long muscles are counteracted by the rotator cuff muscles.

Movement Flexion (150°– 170°) Extension (40°) Muscles Origin Anterior fibers of deltoid Clavicle Clavicular part of pectoralis major Clavicle Short head of biceps brachii Supraglenoid tubercle of scapula Coracoid process of scapula Coracobrachialis Coracoid process Posterior fibers of deltoid Spine of scapula Latissimus dorsi Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower 3– 4 ribs, inferior angle of scapula Long head of biceps brachii Teres major Abduction (160°– 180°) Adduction (30°– 40°) Middle fibers of deltoid Supraspinatus Sternal part of pectoralis major Latissimus dorsi Teres major Teres minor Infraspinatus Lateral rotation (in abduction: 95°; in adduction: 70°) Teres minor Posterior fibers of deltoid Subscapularis Insertion Middle of lateral surface of shaft of humerus Lateral lip of bicipital groove of humerus Tuberosity of radius, Deep fascia of forearm Medial aspect of shaft of humerus Middle of lateral surface of shaft of humerus Floor of bicipital groove of humerus Medial lip of bicipital groove of humerus Middle of lateral surface of Acromion process of scapula shaft of humerus Supraspinous fossa of scapula Greater tuberosity of humerus Sternum, upper six costal Lateral lip of bicipital groove cartilages of humerus Iliac crest, lumbar fascia, spines of lower six thoracic Floor of bicipital groove of vertebrae, lower 3 -4 ribs, humerus inferior angle of scapula Lower third of lateral border Medial lip of bicipital groove of of scapula humerus Upper two thirds of lateral Greater tuberosity of humerus border of scapula Infraspinous fossa of scapula Greater tuberosity of humerus Upper two thirds of lateral Greater tuberosity of humerus border of scapula Middle of lateral surface of Spine of scapula shaft of humerus Subscapular fossa Lesser tuberosity of humerus Lateral border of scapula