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Glenohumeral joint

In fact, it is the most mobile joint of the human body. This shoulder function comes at the cost of stability however, as the bony surfaces offer little support. Instead the surrounding shoulder muscles and ligamentous structures offer the joint security; the capsule, ligaments and tendons of the rotator cuff muscles. Because of this mobility-stability compromise, the shoulder joint is one of the most frequently injured joints of the body.

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Articles of Interest

Normal Anatomy of the Shoulder Joint

The shoulder is the most flexible joint in the body making it the most susceptible to instability and injury. It is a ‘ball-and-socket’ joint. A ‘ball’ at the top of the upper arm bone, humerus, fits neatly into a ‘socket’, called the glenoid, which is part of the shoulder blade, scapula.

What Type Of Joint Is The Shoulder?

Because the shoulder joint is a ball and socket joint, it has 3 degrees of freedom or motion. A hinge joint like the elbow or knee, only has 2 motions or flexion and extension. The shoulder does not fall into this category mainly due to it being the most mobile joint in the body. Also, It is the most unstable joint in the body due to the amount of motion it allows. The shoulder’s main stability is provided by 4 muscles, which are the muscles that make up the rotator cuff. If those muscles become weak or deficient, the shoulder mechanics can become disrupted, leading to tendonitis, arthritis, or instability.

Resources

Physiopedia

The shoulder complex is the connection of the upper arm and the thorax. Comprising numerous ligamentous and muscular structures, composed of the clavicle, scapula, humerus and sternum, and an intricately designed combination of four joints, the Glenohumeral (GH) Joint, the Acromioclavicular (AC) Joint and the Sternoclavicular (SC) Joint, and a "floating joint", known as the Scapulothoracic (ST) joint. The shoulder allows for a large range of motion due to the spheroid shape of the glenohumeral joint but this (i.e. a large ball in a small socket) renders it prone to dislocation and other injuries.

Teachme Anatomy

The shoulder joint (glenohumeral joint) is an articulation between the scapula and the humerus. It is a ball and socket-type synovial joint, and one of the most mobile joints in the human body.