Causes

The cause of impingement of tendons under the acromion (to impinge) can be either in the connective tissue structures of the shoulder joint (tendons, capsule-ligament apparatus) or in the bony parts. The main cause is the tendon of the supraspinatus muscle, which can swell by up to 1 cm. due to degenerative processes and is then disturbed in its running and sliding behavior.

However, other tendons of the shoulder musculature (mainly the tendons of the so-called rotator cuff (rotating muscles of the shoulder joint, which centers the shoulder head in the joint when under tension), ligament connections, parts of the shoulder joint capsule or the bursa under the bony acromion can also be affected. Another cause is the so-called shoulder joint instability. This means that the joint is not able to assume an anatomically correct position between the head and socket during normal movements and loads.

In 85% of cases, the head of the shoulder joint has slipped upwards, forward (subluxation, is favored by the anatomy) and then leads to entrapment of the tendons when the arm is raised. Even minimal shoulder instability results in increased activity of the shoulder joint muscles, which leads to tension, trigger points and ultimately muscular imbalance. Bony causesBony causes are often found in the anatomical shape of the acromion or in the joint between the acromion and the collarbone. There, a calcium deposit (tendinosis calcarea) may be located in the already narrow tunnel between the acromion and the roof, or a curved acromion or a bone spur may narrow the tunnel further. Degenerative changes such as arthrosis of the acromioclavicular joint can also cause an impingement syndrome.Since the space between the acromion and the shoulder condyle is anatomically quite narrow and narrows further from about 60° during the abduction movement, slight thickening of the tendons or bones is sufficient to trigger the pain during the abduction movement by trapping the tendons.

PrimarySecondary Impingement

In primary impingement, the cause is located in the space between the acromion and the head of the shoulder joint (soft tissue or bone), pain triggers are located directly in the shoulder joint. Secondary impingement refers to all disorders that trigger similar pain symptoms in the glenohumeral joint but are otherwise caused by the musculoskeletal system and/or internal organs. These can be functional disorders in. This form of shoulder pain is often wrongly diagnosed and treated as impingement syndrome.

The cervical spine
The thoracic vertebral or rib joints
Muscular imbalances in the shoulder joint and shoulder girdle
A strong hunchback, nerve irritation of the shoulder and
Arm-supplying nerves or disturbances in the gallbladder or liver (right shoulder pain) or
In the stomach (left shoulder pain)