Believe it or not, your shoulder joint has more range of movement than nearly every other joint in your body. This is because the shoulder is involved in numerous activities – many that you don’t even think about. Whether you’re stirring a pot, playing ball, or even just getting dressed, your shoulder is involved in some way.
Unfortunately, the enormous range of flexibility our shoulder has also means that it’s one of the most unstable joints in the body.
As we age, wear and tear takes a toll on the joint, which is why older people are more vulnerable to shoulder problems. Athletes, painters, laborers and other people involved in physical activity are also at risk.
While the shoulder itself is made of bone, the shoulder joint is held together with a complex system of muscles, ligaments and tendons. It’s important to note that this not a single joint.
Functions of the shoulder depend on the ability of this joint to provide strength and range of motion to the arm.
The Different Shoulder Functions
The shoulder “girdle” is the set of bones connecting to the arm. This comprises of the clavicle, scapula and humerus. The functions of the shoulder involve the ability of these bones to move with the tendons and ligaments with the cavity.
The deepest layer of the shoulder is bone. This is followed by ligaments of the joint capsule, then the tendons and muscles. The shoulder is is supplied by blood vessels and nerves. Nerves carry signals to and from the brain to the muscles, providing instructions for movement, pain and temperature.
The shoulder joint is also referred to the glenohumeral joint, which is its main joint. The glenohumeral joint is essentially a ‘ball and socket’ joint, which allows the arm to move up, down, in circles or away from the body. The ball fits into a soft tissue capsule that surrounds the glenohumeral joint. This is attached to the scapula, humerus, and head of the biceps, and is linked by a thin synovial membrane. The four muscles surrounding the joint are known as the rotator cuff, and play a large part in stabilizing the shoulder. The rotator cuff attaches to the glenohumeral capsule and the humeral head.
The intricate design of the ligaments and tendons are crucial to functions of the shoulder. Along with the muscles, these ligaments and tendons are what allow the shoulder to move through an enormous range of motions. Functions of a healthy shoulder include:
- Abduction: moving the arms away from the midline of the body
- Adduction: moving the arms toward the body’s midline
- Rotation of the arms
- Raising the arms overhead
- Moving the shoulder through a full 360° in the sagittal plane.
Of course, these many movements mean the shoulder more prone to dislocation and injury than any other joints in the human body. Injuries to the shoulder can result in pain and loss of function, which can severely debilitating for those involved in sporting activities or manual labor.