Glenohumeral Joint Lab Report

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Introduction
Glenouhumeral Joint The glenohumeral (GH) joint, which is also known as shoulder joint, is a multiaxial ball-and-socket synovial joint. This joint is responsible for connecting the upper extremity of the trunk. The glenohumeral joint is one of the four joints that comprise the shoulder complex. The joint is considered to be the most mobile and least stable joint. The articular surfaces of the glenohumeral joint are the head of humerus and glenoid fossa of scapula. The humeral head can be in articulation with the glenoid fossa in any position of joint because the head of the humerus is larger than the glenoid fossa. This relationship is best compared with a golf ball siting on a tee, with stability conferred by static and dynamic
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The superior glenohumeral ligament travels laterally from the upper part of the glenoid labrum and the base of the coracoid process to the upper part of the humerus between the upper part of the lesser tuberosity and the anatomical neck. The superior glenohumeral ligament contributes very little to static stability of the glenohumeral joint. However, this ligament helps to keep the humeral head suspended. The middle glenohumeral ligament has a wide attachment extending from the superior glenohumeral ligament along the anterior margin of the glenoid fossa down as far as the junction of the middle and inferior thirds of the glenoid rim. In addition, the middle glenohumeral ligament limits lateral rotation up to 90 degrees of abduction. Also, the middle glenohumeral ligament is an important anterior stabilizer of the shoulder joint. The inferior glenohumeral ligament attaches to the anterior, inferior and posterior margins of the glenoid labrum and goes through laterally to the inferior aspects of the anatomical and surgical necks of the humerus. Hence, this ligament supports the joint most effectively in the upper ranges of abduction.

Rotator cuff
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This changes in orientation and makes the movement at glenohumeral joint. During the first 30 degrees of shoulder abduction, the scapula remains stationary against the ribcage if the movement only occurs at glenohumeral joint. As shoulder abduction continues, the inferior angle of the scapula begins to shift upwards as it undergoes superior angle rotation. Hence this bring about for every 2 degrees of glenohumeral joint moves, 1 degree of scapulathoracic moves from this point. When the upper extremity moves abduction on the 90 degrees, the upper glenohumeral joint contributes 40 degrees for a total of 70 degrees while the scapulathoracic only contributes 20 degrees. This ratio continues above 90 degrees so that by the time it have been rasied to 180 degrees. The contribution of each joint will be 110 degrees of glenohumeral and 40 degrees scapulothoracic.

The muscles to maintain the scapulathoracic stability and motion are serratus anterior, rhomboids, levator scapulae and

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