The primary ligaments connecting the shoulder to the arm are the glenohumeral ligaments.
Glenohumeral Ligaments (GHLs) Explained
The glenohumeral ligaments are a group of ligaments that are essential for shoulder stability. They connect the humerus (the upper arm bone) to the glenoid (the socket part of the shoulder blade or scapula). Specifically, they help stabilize the shoulder joint, preventing dislocations and excessive movement. There are typically three glenohumeral ligaments:
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Superior Glenohumeral Ligament (SGHL): This ligament primarily stabilizes the shoulder against inferior (downward) translation of the humerus when the arm is adducted (close to the body). It also contributes to limiting external rotation when the arm is at the side.
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Middle Glenohumeral Ligament (MGHL): The MGHL stabilizes the shoulder when the arm is abducted (raised away from the body) and externally rotated.
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Inferior Glenohumeral Ligament Complex (IGHLC): This is the strongest and most important of the glenohumeral ligaments. It has anterior and posterior bands, and it provides the most significant stability during abduction and external rotation. It is vital in preventing anterior dislocation of the shoulder.
Other Contributing Ligaments
While the glenohumeral ligaments are the primary ligaments from the shoulder to the arm, other ligaments also play a role in shoulder stability, although they don't directly connect the arm to the shoulder blade in the same way. These include:
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Coracohumeral Ligament: This ligament runs from the coracoid process (a bony projection on the scapula) to the humerus. It helps support the arm against gravity and limit external rotation when the arm is adducted.
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Transverse Humeral Ligament: This ligament bridges over the bicipital groove of the humerus, helping to keep the biceps tendon in place.
In summary, when referring to the "ligament from the shoulder to the arm," the glenohumeral ligaments are the key structures to consider. They are crucial for the stability and proper function of the shoulder joint.
