Glenohumeral Joint Structure
an educational animation

Glenohumeral Joint Structure
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Get Massage Smart thanks every individual involved on the 3D Anatomy Lyon projects, please see credits below. The glenohumeral joint structure is often referred to as the shoulder joint.  To understand the shoulder joint it is necessary to understand that there are multiple joints involved within the pectoral girdle allowing for a wide range of motion.  Three true joints and two false joints.  A true joint is where two bones come together to form an articulation, usually involving articular cartilage, ligaments and tendons.  A false joint is formed when two bones lie very close to each other but do not directly articulate and do not share surfaces lined with articular cartilage. 

The glenohumeral joint is the articulation between the head of the humerus and the glenoid fossa of the scapula.  The glenohumeral joint structure is a true joint with a significant range of motion.  The scapula is anchored to the trunk of the body via the clavicle.  The clavicle forms one articulation with the scapula the acromioclavicular joint and one with the breast bone or sternum the sternoclavicular joint.  Both the acromioclavicular joint and the sternoclavicular joint are true joints.  The additional motion allowed by scapular movements and clavicular movements greatly increase the range of motion within the pectoral girdle.

So where are the false joints and how do they come into play?  The large flat portion of the scapula that lies against the rib cage is referred to as the scapulothorasic joint and is a false joint.  The surface of the subscapular fossa is covered with the subscapularis muscle and the serratus anterior lies over the ribs and anchors the scapula to the rib cage.  While the surface of the ribs are covered by fascia and anchored to each other by the intercostal musculature.

The next false joint is not agreed upon by all anatomists.  The subdeltoid space can narrow leading to shoulder impingement syndrome.  When the arm is raised overhead the head of the humerus rotates upward toward the acromion process of the scapula allowing for a portion of the lateral edge of the humerus at and below the greater trochanter to come very close to the undersurface of the acromion process.  This is why some anatomists refer to this spacing as the subdeltoid joint.

Not included in our joint count for the pectoral girdle are the thoracic intervertebral joints and the lumbar intervertebral joints.  To allow for the greatest range of motion within the motion of the pectoral girdle these joints of the spinal column play a small but vital role.  To visualize the "humero-scapluo-spinal" rhythm watch anatomy Lyon's video titled "the shoulder".

Glenohumeral Joint Structure
A Closer look at the Ligaments and Joint Capsule

The head to the humerus:

is 1/3 of a sphere, the sphere is three times larger than the glenoid fossa

the articular surface of the sphere is oriented inward and behind

The glenoid fossa or cavity:

is oval, shallow and wider at the bottom

the fossa is almost flat with a small edge at the bottom

The glenoid cavity:

the glenoid labrum slightly increases the depth of the fossa forming the glenoid cavity

the glenoid labrum is a fibro cartilage that completes the glenoid surface

The glenoid labrum:

the peripheral side of the labrum attaches to the joint capsule

the labrum in triangular in shape upon sectioning and is covered with cartilage

The glenoid labrum:

the medial side of the labrum attaches to the glenoid fossa

The glenohumeral joint capsule:

References and Resources:

These videos are offered for their educational value and accuracy of mateiral is not validated by getmassagesmart.com.  The videos were published on YouTube on November 13, 2013  by the YouTube channel 3D Anatomy Lyon. Get Massage Smart thanks the Authors of these educational videos Patrice Thiriet and Jean-Michel Grand and for realization Olivier Rastello.  Video reference material was take from: J.M. Grand Master Thesis June 2, 2011 * M. Dufour et M Pillu; Biomecanique Functionnelle - Ed Masson 2008 * J.C. Chanussot et R. G. Danowski; Reeducation en traumatologie du sport - Tome 1 - Ed. Masson 2005 * A. I. Kapandji; Anatomic Funtionelle - Ed. Maloine. 



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