Glenohumeral Joint
Copyright 2010
Definition
The shoulder joint is the part of the musculoskeletal system that enables the upper limb to connect to the axial skeleton. The shoulder as a structure consists of a group of accessory components including cartilage, synovium, muscle, ligament, and tendons that surround the joint and faciliate the ball and socket articulation and enable the characteristic wide range of motion.
The bony components of the shoulder include the scapula and humerus. The scapula contributes the glenoid, acromion and coracoid process to the joint. The humeral head fits into this triad of scapular structures and the joint is deepened by the fibrocartilagenous labrum that surrounds the the glenoid cavity to deepen the articulating surface. The humerus has been likened to a golf ball and the scapiula to a tee.
The articular surfaces are covered with hyaline cartilage.
The ligaments of the shoulder include the glenohumeral ligaments, transverse humeral ligament, coracoacromial ligament and the coracohumeral ligament.
The bursae include the subscapular bursa and the subacromial bursa. The subscapular bursa is located between the subscapularis tendon and the scapular neck. The subacromial bursa is located between the acromion, coracoacromial ligament, the deltoid, supraspinatus tendon, and the joint capsule.
The blood supply is from the anterior and posterior circumflex arteries and from branches of the suprascapular artery.
The innervation is from the suprascapular, axillary, and lateral pectoral nerves.
The glenohumeral joint’s components as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.
The function of the glenohumeral joint is to permit movement of the upper extremity in flexion-extension, abduction-adduction, medial and lateral rotation, and circumduction. Circumduction is a sequence of flexion, abduction, extension, and adduction or the reverse.
The shoulder flexors are the pectoralis major, anterior deltoid, and the coracobrachialis.
The shoulder extensors are the posterior deltoid and the teres major.
The shoulder abductors are the deltoid and the supraspinatus.
The shoulder adductors are the pectoralis major, latissimus dorsi, subscapularis, infraspinatus, and the teres minor.
The medial rotators of the shoulder are the subscapularis, pectoralis major, anterior deltoid, and the latissimus dorsi.
The lateral rotators of the shoulder are the infraspinatus, teres minor, and the posterior deltoid.
The articular capsule tensors are the subscapularis, infraspinatus, supraspinatus, and teres minor.
The shunt muscles that help to resist dislocation downward are the deltoid, long head of the triceps, coracobrachialis, and the short head of the biceps.
Common diseases of the glenohumeral joint include arthritis, fractures, dislocation/subluxation, septic arthritis, Lyme arthritis, bursitis, tendinitis, impingement syndrome, rotator cuff tendinitis, biceps tendinitis, rotator cuff tears, rotator cuff arthropathy, frozen shoulder, labrum tears.
Fractures can occur in the scapular or humeral components of the glenohumeral joint.
Osteoarthritis is a condition of joint space narrowing leading to pain. Rheumatoid arthritis is a condition of an autoimmune reaction against the synovial tissue.
The glenoid labrum can become torn.
Impingement syndrome is microtrauma to the rotator cuff due to decreased space between the humeral head and the structure located superior to the rotator cuff. Overhead activities usually are painful.
Rotator cuff tendinitis is a condition of overuse resulting in inflammation of the rotator cuff. The most common tendon involved is the supraspinatus tendon. It can result from impingement syndrome or from shoulder instability. Patients may wake up at night with pain.
Rotator cuff tears can be partial or complete tears of any of the muscles of the rotator cuff. The most common cuff tear is the supraspinatus. Patients have pain at night, with overhead activities, and when reaching behind the neck. The tear can be acute or from chronic degenerative changes.
Rotator cuff tear arthropathy is a condition consisting of a large rotator cuff tear, osteoporosis, cartilage loss, and collapse of the humeral head. Patients lose range of motion in the shoulder and there are significant arthritic changes on x-ray.
Frozen shoulder/adhesive capsulitis is a condition of inflammation and stiffness of the shoulder due to adhesion formation.
Bursitis can occur at either the subacromial or the subscapular bursa due to overuse/friction leading to inflammation of the bursa.
Dislocation/subluxation is an injury to the ligaments resulting in displacement of the clavicle humeral head. This is usually due to a trauma. The glenohumeral joint usually dislocates anteriorly, however during an epileptic seizure, a posterior dislocation can occur.
Transient synovitis or toxic synovitis is joint pain after a recent viral illness or trauma. It is a self-limiting condition of patients between ages 3 to 8 years.
Lyme Arthritis is a condition common in the northeast USA where there is a rheumatologic reaction to Borrelia burgdoferi. It occurs after the patient is bitten by a tick.
Osteomyelitis is an infection of the bone typically caused by a bacteria.
Osteoporosis is a condition of low bone mineral density that can predispose an individual to fractures.
Septic arthritis is an infection of the synovial tissue of the joint with pus in the joint cavity. The infection is capable of rapidly destroying the joint.
Commonly used diagnostic procedures include clinical history, physical exam, x-ray, CT, and MRI.
It is usually treated with rest, NSAIDs, physical therapy, and possibly surgery. Dislocation/subluxation and fractures may not respond to nonoperative treatments and may require surgery. Arthritis can be treated with NSAIDs and physical therapy, but may require surgery to remove part of the distal clavicle. Impingement syndrome is treated with rest from overhead activities, physical therapy, NSAIDs, and steroid injections. Surgery can be done if nonoperative measures do not relieve symptoms. Rotator cuff tendinitis and bursitis are treated with rest, NSAIDs, physical therapy, and corticosteroid injections. Rotator cuff tears can be treated with physical therapy and NSAIDs or with surgical repair. Rotator cuff tear arthropathy is treated nonoperatively with physical therapy, NSAIDs, steroid injections, and activity modification. Some patients require arthroscopy of the shoulder or a shoulder arthroplasty. Septic arthritis requires surgical washout and antibiotics. Transient synovitis is treated with NSAIDs. Labral tears can be treated with physical therapy or with arthroscopic repair. Frozen shoulder is initially treated with NSAIDs, physical therapy, and steroid injections. Surgery may be necessary to remove scar tissue and cut the tight ligaments.
References
Davis MF, Davis PF, Ross DS. Expert Guide to Sports Medicine. ACP Series, 2005.
Elstrom J, Virkus W, Pankovich (eds), Handbook of Fractures (3rd edition), McGraw Hill, New York, NY, 2006.
Koval K, Zuckerman J (eds), Handbook of Fractures (3rd edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.
Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Wheeless’ Textbook of Orthopaedics: Glenohumeral Joint (http://www.wheelessonline.com/ortho/glenohumeral_joint)