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THE SHOULDER JOINT Learning Objectives At the end of the presentation, the student should be able to : Classify the type of shoulder joint. Describe the structure of shoulder joint. Name the muscles acting on the joint/rotator cuff muscles. Explain the range of motion. Let know the movements of shoulder joint. What is clinical aspect of the structure? THE SHOULDER JOINT LECTURE OUTLINE The Human Shoulder: The shoulder is a highly mobile joint that allows large range of motion in all planes to provide a variety of overhead activities. The shoulder complex as a whole is unique in that it relies very little on bony and ligamentous structures for stability - with a majority of support coming from 18 muscles acting on the shoulder complex. The Shoulder Joint: Multiaxial spheroidal joint. Skeletally the joint is weak, depends for support on surrounding muscles more than on its shape and ligaments. Articular surfaces; spheroidal humeral head and concave glenoid cavity. Glenoid labrum deepens the cavity.. Both articular surfaces are covered with hyaline cartilage. Wide range of motion of the shoulder joint in many different planes require a significant amount of laxity. The price of mobility is reduced stability. The more mobile a joint is, the less stable it is & the more stable it is the less mobile. Factors Stabilizing The Joint: Coracoacromial arch or Secondary socket for the head of humerus. Glenoid labrum. Musculotendinous cuff of the shoulder. Ligaments: CAPSULAR LIGAMENT. CORACOHUMERAL LIGAMENT. TRANSVERSE HUMERAL LIGAMENT. GLENOID LABRUM. Articular Capsule Of The Glenohumeral Joint: The loose fibrous capsule surrounds the glenohumeral joint and is attached medially to the margin of the glenoid cavity and laterally to the anatomical neck. Superiorly this part of the articular capsule encroaches on the root of the coracoid process so that the fibrous capsule encloses the proximal attachment of the long head of the biceps brachii supraglenoid tubercle of the scapula - within the joint. The capsule is lined with synovial membrane which forms a tubular sheath for tendon of biceps. Ligaments Of The Glenohumeral Joint: The coracohumeral ligament is a strong, broad band that passes from the base of the coracoid process to the anterior aspect of the greater tubercle of the humerus. This ligament resists the pull of gravity and limits external rotation of the shoulder. The glenohumeral (shoulder) ligaments, which strengthen the anterior aspect of the articular capsule of the joint, and the coracohumeral ligament, which strengthens the capsule superiorly, are intrinsic ligaments - part of the fibrous capsule. The glenohumeral ligaments are three fibrous bands - evident only on the internal aspect of the capsule - that reinforce the anterior part of the articular capsule. They radiate laterally and inferiorly from the glenoid labrum at the supraglenoid tubercle of the scapula and blend distally with the fibrous capsule as it attaches to the anatomical neck of the humerus. Superior Glenohumeral Ligament From Upper origin of the glenoid. To Anatomical neck of the humerus. This ligament is taut during external rotation and plays a small role in the stability of the shoulder. Middle Glenohumeral Ligament From Upper origin of the glenoid To Humerus This ligament is taut during external rotation and plays a small role in stability of the shoulder. Inferior Glenohumeral Ligament : Anterior edge of glenoid Below the head of the humerus This ligament is taut during external rotation, and plays a small role in stability of the shoulder. The transverse ligament is not a “true” ligament of the joint. It is a broad fibrous band that runs more or less obliquely from the greater to the lesser tubercle of the humerus, bridging over the intertubercular groove. This ligament keeps the biceps tendon in its groove during movements. Glenoid labrum: Fibrocartilagenous rim which deepens the glenoid cavity. Slightly enhances stability. Glenohumeral Joint: Frequently injured due to anatomical design: – Shallowness of glenoid fossa. – Laxity of ligamentous structures. – Anterior or anteroinferior glenohumeral subluxations & dislocations – common. – Posterior dislocations – rare. – Posterior instability problems somewhat common. Bursae: Subacromial bursa(subdeltoid bursa) Subcapsular bursa, communicates with the joint cavity. Others related to corachobrachialis, long head of triceps. Rotator cuff muscles: Take origin from scapula and inserted to greater and lesser tubercles of humerus. Their tendons become flattened and blend with each other and the capsule while crossing the joint. Supraspinatus: O: Supraspinous fossa. I: Superior facet on greater tubercle of humerus. A: Initiates and assists Deltoid in abduction; acts with other rotator cuff muscles. N: Suprascapular Nerve. Infraspinatus: O: Infraspinous fossa. I: Middle facet on greater tubercle of humerus. A: Laterally rotates the arm. N: Suprascapular Nerve. Teres minor: O: Superior part of the lateral border of the scapula I: Inferior facet on greater tubercle of humerus A: Laterally rotates the arm N: Axillary Nerve Subscapularis: O: Subscapular fossa. I: Lesser tubercle of humerus. A: Medial rotation of arm and adduction. N: Upper and Lower Subscapular. Movements: Abduction: – upward lateral movement of humerus out to the side, away from body Adduction: – downward movement of humerus medially toward body from abduction • Flexion: – movement of humerus straight anteriorly. • Extension: – movement of humerus straight posteriorly. • Horizontal adduction (transverse flexion): – movement of humerus in a horizontal or transverse plane toward & across chest. • Horizontal abduction (transverse extension): – movement of humerus in a horizontal or transverse plane away from chest • External rotation: – movement of humerus laterally around its long axis away from midline • Internal rotation: – movement of humerus medially around its long axis toward midline. Muscles: • Anterior: – Pectoralis major – Corachobrachialis. – Subscapularis. • Superior: – Deltoid. – Supraspinatus. Deltoid Muscle: Anterior fibers: abduction, flexion, horizontal adduction, & internal rotation. Posterior fibers: abduction, extension, horizontal abduction, & external rotation. Middle fibers: abduction Pectoralis Major Muscle: Upper fibers (clavicular head): internal rotation, horizontal adduction, flexion, abduction (once arm is abducted 90 degrees, upper fibers assist in further abduction), & adduction (with arm below 90 degrees of abduction). Lower fibers (sternal head): internal rotation, horizontal adduction, extension, & adduction Latissimus Dorsi Muscle: Adduction. Extension. Internal rotation. Horizontal abduction. Coracobrachialis Muscle: Flexion. Adduction. Horizontal adduction Rotator Cuff Tendonitis: Rotator cuff tendonitis, also knows as "BURSITIS" OR "IMPINGEMENT SYNDROME" OCCURS WHEN THE ROTATOR CUFF GETS irritated on the undersurface of the acromion. Chief complaints are pain, popping, weakness and the inability to sleep on the affected limb. Rotator Cuff Tear: A rotator cuff tear occurs when the tendonitis in the rotator cuff gets so bad that it wears a hole through the rotator cuff tendon. It can be acute or chronic. Chief complaints are pain, popping, stiffness, weakness, and inability to sleep on the affected limb. Frozen shoulder: • No visible abnormality detected on X-RAYS. THANK YOU