Unlike the lower extremity, the shoulder does not have to carry the entire load of the human body. It is also exempt from locomotion. For this reason, it has a wide range of motion. However, it is also more often affected by disease than other joints.
What is the shoulder?
Schematic diagram showing the anatomy of the shoulder. Click to enlarge. The shoulder is defined as the large area around the four shoulder joints. The clavicle and scapula represent the bony foundation of the shoulder. In a broader sense, the so-called “caput humeri”, the head of the humerus, is also counted as part of the shoulder. The shoulder girdle is composed of several bones. These include the clavicle and scapula.
Anatomy and structure
In addition to the joint that connects the humerus and clavicle, three other joints are found in the shoulder. Joints are movable connections of at least two bones. The middle clavicle joint connects the sternum and clavicle. It is the only joint that connects the trunk and shoulder girdle. As a result, the joint provides essential movement of the scapula relative to the trunk. The lateral clavicle joint (known as the acromioclavicular joint) connects the clavicle to the so-called acromion, a bony prominence of the scapula. Often this joint is responsible for shoulder pain because it tends to wear out relatively quickly. The “scapulothoracic joint,” which by definition is not a true joint, allows the scapula to slide on the rib cage. The joints are secured by ligaments. This is to prevent the bone from slipping out of its socket. However, ligament securement is inadequate. Therefore, the muscles of the shoulder region are of particular importance. They secure the shoulder joint as far as possible. But also the movements are only made possible by the muscles. In addition, the muscles have an important function in supporting breathing.
Functions and tasks
In the course of development, the functions of the shoulder expanded. Hand motor skills became more specialized, so that grasping movements became more refined. Through the shoulder, humans are able to perform movements on a large scale. The movements are not only limited to the shoulder blade or the shoulder girdle. The shoulder is also significantly involved in the movement of the two upper arms. You can move the upper arm in all directions in the shoulder joint, because the shoulder joint is a so-called ball and socket joint. Many different types of movement are made possible through the shoulder joints. The shoulder can be raised up to 40 degrees. This movement is popularly known as “shoulder shrugging”. The shoulder can be lowered up to 10 degrees. In addition, the shoulder can be moved forward up to 30 degrees, creating a “hump.” Backward, a person can pull the shoulder up to 25 degrees. One makes a “proud chest,” so to speak. Another function of the shoulder is to assist in lifting the arm. This is achieved by rotation in the shoulder blade.
Diseases and complaints
Because of the exceedingly large range of motion that the shoulder allows, the shoulder is increasingly affected by diseases. However, these are different than typical diseases of the knee and hip joints. The knee and hip joints, namely, carry the entire trunk load. For this reason, the most common disease is joint wear and tear: osteoarthritis. The shoulder, on the other hand, is frequently affected by so-called dislocations due to the comparatively weak joint support. A dislocation is the loss of contact between two bones, popularly known as a “dislocated” or “dislocated” joint. In addition, fractures in the shoulder area easily occur in falls or accidents. The most common of these is a fracture of the collarbone. Another typical complaint is shoulder pain due to soft tissue changes. Calcification or small tears can occur in muscles or tendons, causing pain, for example, when moving the arm. However, causes of shoulder pain are often found outside the shoulder region. Thus, diseases of the abdominal or thoracic organs or changes in the cervical spine can also trigger shoulder pain. For this reason, a specialist (e.g. orthopedist) should be consulted in case of long-lasting complaints in the shoulder region.
