Synonym
Acromioclavicular joint, Articulatio acromioclaviculare, AC joint
Definition
The acromioclavicular joint is one of a total of five joints in the shoulder area, it serves primarily to stabilize the shoulder.
Anatomy
The AC-joint is the joint between the two. Usually there is a small intermediate disc, a discus, between the two, it consists of fibrous cartilage and is intended to prevent abrasion of the two ends of the bone due to stress. This discus is subject to a more or less natural degeneration, so that with age in the X-ray image often a
- The outer part of the clavicle and
- A bony protrusion on the upper part of the shoulder blade, the so-called acromion.
- Narrower joint gap due to a
- Almost completely “used up” discus can be seen.
Often, however, this does not cause the person concerned any complaints.
The AC joint is a flat joint, so there is no joint cavity that surrounds the joint head and thus secures it. Therefore, the joint must be secured by strong ligaments, which leads to a rather low degree of movement. Three ligaments ensure the cohesion of the joint.
- The ligamentum acromioclaviculare extends from the acromion to the lateral clavicle.
- The Ligamentum coracoacromiale moves from an extension of the scapula, which resembles a raven’s beak in its appearance and is therefore called Processus coracoideus, to the acromion.
- The Ligamentum coracoclaviculare moves from the processus coracoideus to the collarbone, it starts here further inside than the Ligamentum acromioclaviculare.
- The Ligamentum coracoclaviculare consists of two parts, the Ligamentum trapezoideum, which runs further outwards (laterally) and the Ligamentum conoideum.
Function
The AC joint is involved in the movement of the shoulder joint, but does not have an autonomous function here. A functional disorder of the joint is therefore not characterized by a loss of mobility, but rather by instability of the shoulder.
