Function of the rotator cuff
The function for arm movement of each muscle involved in the rotator cuff has already been described.In summary, the rotator cuff plays a major role in the rotation of the arm, i.e. the outer and inner rotation of the upper arm. The rotator cuff is therefore extremely important for the mobility of the whole arm. Together with other muscles, the rotator cuff gives the shoulder joint the greatest range of motion of all human joints.
In addition, each muscle of the rotator cuff tenses the joint capsule of the shoulder joint, thus providing stability to the shoulder joint. Due to the low level of bony guidance of the shoulder joint and the weak ligamentous apparatus, the rotator cuff and the deltoid muscle (deltoid muscle) are mainly responsible for securing the shoulder joint. Together, they ensure that the head of humerus is held (centered) in the glenoid cavity. However, this also explains to the same extent the high loads acting on the rotator cuff and the consequences of injuries resulting from this.
Diseases of the rotator cuff
In contrast to other large joints of the body, the shoulder joint is mainly guided and stabilized by its soft tissues (muscles, ligaments, joint capsule). The contact between the large head of humerus (humerus) and the glenoid cavity is minimal. Due to these enormous loads, diseases of the shoulder joint are more frequently found in the area of the rotator cuff.
The supraspinatus muscle, which runs under the acromion to the humeral head, is particularly frequently affected. When the arm is moved above the horizontal, this muscle is narrowed by the acromion because the head of humerus rises under the acromion when the arm is raised. The clinical picture of impingement syndrome can be caused by a congenital or acquired acromion due to wear and tear.
This refers to the repeated pinching of the supraspinatus tendon under the acromion, which results in inflammation of the tendon and the bursa (bursitis subacromialis) located there. If the load capacity of the supraspinatus tendon is exceeded, it can tear without adequate injury (supraspinatus tendon rupture rotator cuff tear). The German translation of impingement syndrome means bottleneck syndrome, which is also referred to as shoulder bottleneck syndrome.
Chronic damage can also lead to calcium deposits in the supraspinatus tendon, but also in other tendons of the rotator cuff. This is known as the clinical picture of tendinitis calcarea or calcified shoulder. Often, the cause of shoulder pain lies in the area of the rotator cuff.
Most complaints occur under stress, such as when the arm is straddled and especially when trying to lift the arm completely. Symptoms include pain during stress or when lying on the arm, e.g. at night, which even radiates to the hand. Symptoms can also include muscle weakness in the shoulder area and functional limitations.
Typically, tendon changes are the cause of these complaints. Changes in the bone structure, degenerative changes in the tendons, e.g. calcifications that increase with age, or trauma can lead to a constriction of the tendon of the supraspinatus muscle. This entrapment is called impingement syndrome and causes pain that occurs when the arm is lifted above 60° and disappears again when it is lifted above 120°.
This area is also called “Painful Arc”. This phenomenon is based on the fact that when the arm is lifted, the space under the acromion is reduced and the pre-damaged tendon of the supraspinatus muscle running underneath it is pinched. This phenomenon often occurs in athletes, especially swimmers, tennis, golf and handball players.
To confirm the diagnosis, imaging (x-ray, MRI) is often performed. Therapy can be either conservative, i.e. using physiotherapy and various drugs, or operative, i.e. arthroscopy.
Inflammation is often a reaction of the body to injuries and occurs particularly when muscles or tendons are irritated. In the shoulder area, inflammation is often observed in the presence of calcifications. Classic symptoms can be observed in inflammation of the rotator cuff: The shoulder area is reddened compared to the sides, often overheated and swollen, and movement is often restricted and painful.
If the symptoms persist for several days or worsen, a visit to a doctor should be considered.Repeated inflammation can lead to calcification, especially in the area of the tendons, and lead to functional limitations and pain, see impingement syndrome. A detailed medical history and physical examination, a blood sample to measure inflammation parameters and an imaging procedure (e.g. MRI) can help to confirm the diagnosis. However, the shoulder should be spared in any case and a shoulder orthosis or bandage should be worn if possible.
For pain therapy, non-steroidal antirheumatic drugs should be considered. Physical therapy and physiotherapy can help to minimize pain and loss of function. The rotator cuff is indispensable for countless movements that are performed daily and are often accompanied by stress.
With increasing age, the tendons become more and more worn and the risk of rupture, i.e. the probability of a tear, increases. Furthermore, calcification and altered bone structures make the tendons even more brittle. However, the tendons very rarely tear on their own, but rather as a result of trauma, for example after a fall.
The tendon of the supraspinatus muscle is particularly at risk. Due to its close anatomical proximity to the acromion, it is subject to particular stress. A torn rotator cuff usually causes sudden severe pain in the entire shoulder region.
The pain is often also dependent on position and movement: When lying on the affected arm or when lifting from the arm, the pain increases. Pain that occurs at night and impairs the sleep rhythm is also typical. A rotator cuff tear also causes a reduction in strength and limited mobility of the shoulder.
To confirm the diagnosis, an ultrasound or MRI can be performed. To restore the function of the muscle, the tendon should be sutured back together. This is usually done arthroscopically, i.e. using small rods that can be inserted into the shoulder, thus avoiding open surgery. In addition, physiotherapy should be prescribed to restore the strength of the damaged muscle and strengthen the other muscles of the rotator cuff.
