The primary ligaments connecting the shoulder (specifically the scapula) to the arm (humerus) are the coracohumeral ligament and the glenohumeral ligaments.
Ligaments are strong, fibrous connective tissues that connect bones to each other, providing stability and limiting excessive joint movement. In the shoulder, these ligaments play a crucial role in maintaining the integrity of the glenohumeral joint (the main shoulder joint).
Here's a breakdown of each ligament group:
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Coracohumeral Ligament: This strong ligament runs from the coracoid process of the scapula to the greater tubercle of the humerus. It helps to support the superior aspect of the shoulder joint and resists inferior translation (downward movement) of the humerus, especially when the arm is adducted (close to the body).
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Glenohumeral Ligaments: These are a set of three ligaments located on the anterior (front) aspect of the shoulder joint capsule. They provide stability to the shoulder in various positions. The glenohumeral ligaments are often described as superior, middle, and inferior:
- Superior Glenohumeral Ligament (SGHL): The SGHL limits adduction and external rotation when the arm is at the side.
- Middle Glenohumeral Ligament (MGHL): The MGHL limits external rotation and abduction (away from the body), especially when the arm is abducted to 45 degrees.
- Inferior Glenohumeral Ligament Complex (IGHLC): The IGHLC is the most important stabilizer of the shoulder when the arm is abducted above 90 degrees. It has an anterior band, a posterior band, and an axillary pouch. This complex resists anterior and posterior translation of the humerus.
In summary, the ligaments connecting the shoulder to the arm provide crucial stability and help control the range of motion of the shoulder joint.
