Shoulder Anatomy
The shoulder is a complex combination of bones and joints where many muscles act to provide the widest range of motion of any part of the body. Numerous muscles help stabilize the three joints of the shoulder while giving it motion.
At the shoulder, three major bones meet and create a 90-degree angle:Clavicle: Also known as the collarbone, the clavicle extends across the front of the shoulder from the sternum to the scapula. It helps stabilise the shoulder’s movements.Scapula: More commonly known as the shoulder blade, the scapula is a flat triangular bone located in the upper back. It connects with the collarbone at the front of the body.Humerus: The largest bone of the arm, the humerus connects to the scapula and clavicle in the shoulder. The head of the bone is shaped like a ball to create a ball-and-socket joint with the scapula.
The junctions of these three bones and the sternum form three joints:Glenohumeral joint: This shallow ball-and-socket-style joint created by the humerus and scapula allows the arm to rotate circularly and to move up and out from the body. It is surrounded by soft tissue and strengthened by fibrous ligaments.
Acromioclavicular (AC) joint: This joint forms the highest point of the shoulder and provides the ability to raise the arm above the head. The meeting of the scapula and clavicle forms it.Sternoclavicular joint: This joint is at the center of the chest where the clavicle meets the sternum. It allows the clavicles to move.
The shoulder is a ball-and-socket joint that has three main bones: -The humerus (long arm bone), -The clavicle (collarbone), and -The scapula (also known as the shoulder blade).
These bones are cushioned by a layer of cartilage.
There are two main joints:-The acromioclavicular joint is between the highest part of the scapula and the clavicle.
-The glenohumeral joint is made up of the top, ball-shaped part of the humerus bone and the outer edge of the scapula. This joint is also known as the shoulder joint.
The shoulder joint is the most mobile joint in the body. It moves the shoulder forward and backward. It also allows the arm to move in a circular motion and to move up and away from the body.
The rotator cuff
Shoulders get their range of motion from the rotator cuff. The rotator cuff is made up of four tendons. Tendons are the tissues that connect muscles to bone. It may be painful or difficult to lift your arm over your head if the tendons or bones around the rotator cuff are damaged or swollen. You can injure your shoulder by performing manual labor, playing sports, or even by repetitive movement. Certain diseases can bring about pain that travels to the shoulder. These include diseases of the cervical spine (neck), as well as liver, heart, or gallbladder disease.You’re more likely to have problems with your shoulder as you grow older, especially after age 60. This is because the soft tissues surrounding the shoulder tend to degenerate with age.