Shoulder joint

Nicole Wendler holds a PhD in biology in the field of oncology and immunology. As a medical editor, author and proofreader, she works for various publishers, for whom she presents complex and extensive medical issues in a simple, concise and logical manner.

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The shoulder joint is the most flexible joint in our body. The price for this great mobility is that the ball joint is not as stable as other joints in the body. Despite several muscles and ligaments for stabilization, a fall on the shoulder often ends with a dislocated joint. Read everything you need to know about the shoulder joint here!

What is the shoulder joint?

The shoulder joint (articulatio humeri, humeroscapular joint) forms the shoulder together with the shoulder joints, collarbone (clavicle), shoulder blade (scapula) as well as muscles, tendons, ligaments and bursa. It is the junction between the upper arm (humerus) and the shoulder blade. Strictly speaking, this is where the head of the upper arm and the elongated, concave joint socket of the scapula meet. The joint socket is covered with cartilage, which forms a bulging border on the outer edge (labrum glenoidale). This cartilage lip ensures that the relatively large joint head of the upper arm can lie more stable in the much smaller and quite flat joint socket. The joint is enclosed by a relatively thin joint capsule.

Muscles

The shoulder joint is also referred to as a muscle-secured joint, since - unlike the knee joint, which is stabilized by strong ligaments - it is mainly held by numerous muscles. The shoulder muscles primarily include the rotator cuff - a group of four muscles and their tendons that arise on the shoulder blade, enclose the shoulder joint like a cuff and attach to the head of the humerus. Another important muscle of the shoulder joint is the long head of the biceps muscle (Musculus biceps brachii) sitting on the shaft of the humerus.

Tapes

In addition to these muscles, some ligaments and tendons that run from the head of the humerus to the shoulder blade support the movement. Three ligament structures on the front (ligamentum glenohumeralia superius, mediale and inferius) and a ligament in the upper area (ligamentum coracohumerale) play an important role here.

Bursa

Some bursa are positioned around the shoulder joint. As a buffer, they prevent bones from rubbing against bones when moving the arms. In particular, the bursa under the shoulder joint roof (bursa subacromialis) and that between the deltoid muscle and shoulder joint (bursa subdeltoidea) are stressed.

What is the function of the shoulder joint?

The shoulder joint connects the arm to the trunk. Because the ball-and-socket joint is so flexible, the arm can be rotated in all directions: it can be swung forwards and backwards (ante and retroversion), spread apart and brought in (abduction and adduction) and rotated inwards and outwards (inwards and outwards) External rotation). The two adjacent joints are also necessary for this large range of motion: the sternoclavicular joint (joint between the sternum and the clavicle) and the acromioclavicular joint (the joint between the shoulder blade and the collarbone). They are important starting points for the shoulder muscles.

Where is the shoulder joint located?

The shoulder joint is the junction between the humerus and the shoulder blade.

What problems can the shoulder joint cause?

If the shoulder hurts, it is often not the joint itself, but one of the secondary joints, a bursa or the ligaments and muscles involved. The joint capsule can also cause symptoms.

Violence (such as a fall or a traffic accident) can lead, for example, to bruises, strains, ligament or capsule tears in the shoulder area. The shoulder joint can also become dislocated and the bones involved can break (shoulder fracture). When the lip of cartilage tears off at the socket, medical professionals speak of a Bankart lesion.

Discomfort in the shoulder joint can also result from inflammation, such as inflammation of the bursa (bursitis), tendinitis (tendosynovitis), inflammation of the joints (as in rheumatism or gout) or inflammation of the joint mucosa (synovitis).

Other important diseases that affect the shoulder joint include: