The rotator cuff refers to a muscle group of the shoulder. It is of great importance for the mobility and stability of the shoulder joint.
What is the rotator cuff?
The rotator cuff is also known as the muscle-tendon cap. This refers to an important muscle group in the shoulder that includes a total of four muscles. It originates on the shoulder blade (scapula). Together with the ligamentum coracohumerale, the tendons of the muscles form a tough tendon cap. This surrounds the humeral head like a cuff and plays a part in lifting and rotating the arm. It is not uncommon for injuries to the muscle-tendon cap, such as a rotator cuff rupture, to occur.
Anatomy and structure
Composed, the rotator cuff is made up of four muscles. These are the supraspinatus muscle (upper shoulder blade muscle), the infraspinatus muscle (lower shoulder blade muscle), the subscapularis muscle (lower shoulder blade muscle), and the teres minor muscle (small round muscle). The supraspinatus muscle attaches to the upper portion of the posterior surface of the scapula (supraspinous scapula fossa) and runs below the acromion toward the greater tuberosity (lateral humeral head). The muscle serves as a lateral arm lifter, which is especially true during the initial phase of movement when the arm is resting against the body. To a lesser extent, the supraspinatus muscle is involved in external arm rotation. Of all the rotator cuff muscles, it is most at risk for injury. The origin of the infraspinatus muscle is at the inferior portion of the posterior scapular surface (infraspinous scapula fossa). This muscle also runs to the greater tuberosity of the humeral head. At the same time, its position is a little behind the superior scapular muscle. It is the strongest external rotator of the humerus. The subscapularis muscle begins on the anterior side of the scapula (subscapularis scapula fossa) at the minus tuberosity (front side of the humeral head). When the muscle is tensed, the humerus turns to the inside and is pulled toward the body. In this process, the subscapularis muscle forms the most powerful internal humeral rotator. The insertion of the teres minor muscle is located at the lateral edge of the scapula (margo lateralis scapula). Its course also leads to the greater tuberosity. The muscle is classified as a weak humeral external rotator. It is also involved in pulling the upper arm in the direction of the body. The teres minor muscle has the characteristic of being the least injured of the rotator cuff muscles. The supraspinatus muscle is innervated by the suprascapular nerve, which originates in the brachial plexus.
Function and tasks
The most important function of the rotator cuff is external and internal rotation of the upper arm. Thus, the muscle-tendon cap plays an important role in overall arm mobility. Together with other muscles, the rotator cuff provides an extensive range of motion for the shoulder. Furthermore, each individual rotator cuff muscle provides stability to the shoulder joint by tightening the shoulder joint capsule. Since there is only minor bony guidance in the shoulder joint and the ligamentous apparatus presents itself weakly, the rotator cuff as well as the deltoid muscle take over the securing of the shoulder. Together, they provide support for the head of the humerus in the glenoid cavity. One disadvantage, however, is that this places high stresses on the rotator cuff, which in turn leads to negative consequences in the event of injury. If, for example, the rotator cuff tears, the humeral head can no longer be guided precisely, so that it rises in the upper direction. The affected person can then no longer lift the arm properly.
Diseases
Because of the high stresses placed on the rotator cuff, injuries and diseases to this part of the body are not uncommon. In particular, the supraspinatus muscle below the acromion is often affected. For example, shoulder roof tightness, which is either already congenital or develops over time due to wear and tear, can lead to impingement syndrome (tightness syndrome). In this case, the supraspinatus tendon below the acromion is repeatedly pinched. As a result, painful inflammation of the tendon and bursa occurs. One of the most common impairments of the rotator cuff is rotator cuff rupture (rotator cuff tear).The tear can occur in one or more tendons of the rotator cuff muscles. In most cases, however, the injury is seen in the supraspinatus tendon. Men over the age of 30 are particularly affected by a rupture. Common causes of a rotator cuff tear include impingement syndrome, injuries such as falls on the shoulder, and degeneration. Wear and tear is favored by working above the head for several years, as well as overhead sports. These primarily include handball, basketball, golf and tennis. A rotator cuff tear becomes noticeable through different symptoms. Depending on the cause of the rupture, they occur abruptly or occur over a longer period of time. In most cases, the pain depends on the patient’s position and loads. It is not uncommon for those affected to also suffer pain at night when lying on the injured side. Furthermore, there is a risk of more or less pronounced loss of function as well as a complete loss of function of the shoulder joint. If there is chronic damage to the rotator cuff, it is possible that calcium is deposited in the supraspinatus tendon. However, this process can also occur in the other rotator cuff muscles. In medicine, this is referred to as calcified shoulder or tendinitis calcarea. The therapy for an impairment of the rotator cuff depends on the type and extent of the injury. It ranges from physiotherapeutic measures to major surgical procedures in which the affected tendons are sutured.
