If you think about it, there are few daily tasks that don’t involve the use of your shoulders. Because the shoulder is the most movable joint in the body, it is somewhat unstable. Overuse and shoulder instability can lead to several different varieties of shoulder pain.
The shoulder is composed of three bones: the clavicle (collarbone), the scapula
(Shoulder blade), and the humerus (upper arm bone)(Figure 1).
Motion is controlled by two joints:
The acromioclavicular joint (AC joint) and the glenohumeral joint (Figure 2).
The AC joint is located between the acromion and the clavicle while the glenohumeral joint is the ball-and-socket joint that allows the arm to rotate in a circular motion. Supported by muscles, tendons and ligaments, the rotator cuff holds the ball at the top of the humerus in the socket and provides strength and mobility to the shoulder joint. Injuries often arise from the shoulder’s soft tissue being over- or underused. In addition, the shoulder’s anatomy can also play a role in shoulder pain. Common shoulder pain causes include tendonitis, bursitis, injury/instability, arthritis, rotator cuff tears and fractures.
Tendonitis often causes pain which is the result of the tendon being overused. A tendon connects the muscle to bone or other tissue.
Tendonitisis usually the result of degenerative changes that take place over several years.
This can be car characterized either as an acute (following an overuse problem) Injury or a chronic (degenerative disease due to age) injury.
Bursitis is another overuse disease that affects the shoulder. Excessive use often leads to inflammation of the bursa–the fluid filled sac around the joints–which may limit the use of the shoulder. The bursa is responsible for lessening the friction caused by shoulder movement.
Shoulder instability is a common problem that results in shoulder pain. Because the ball of the upper arm is larger than the socket that holds it, it is often subject to injury. This anatomical anomaly causes instability if muscles, and tendons or ligaments are disrupted.
Another common shoulder problem is a dislocated shoulder
The shoulder joint it the most commonly dislocated joint in the body and is usually has a high recurrence rate in young patients. Shoulder dislocation is usually caused by a strong force that pulls the shoulder outward, popping the ball of the humerus out of the shoulder socket. Often, this motion overwhelms the muscles because they are unprepared to resist the excessive force. Putting the shoulder back into position is accomplished through a process called reduction. This procedure is usually done while the patient is sedated or relaxed. Dislocations may be associated with nerve injuries such as the axillary nerve and brachial plexus. If a young patient is unable to lift his or her arms following reduction of a shoulder dislocation, there is usually an axillary nerve injury. However, if an elderly patient is unable to lift his or her arms following reduction of a shoulder dislocation, there is usually a rotator cuff tear. An MRI may be necessary to determine the injury.
Another shoulder injury patients often experience is a separated shoulder. A separated shoulder results when a force separates the collarbone from the shoulder blade. The shoulder blade moves downward from the weight of the arm and creates a bump or bulge above the shoulder.
Arthritis and rotator cuff tears can also occur. Arthritis involves wear-and-tear changes with inflammation of the joint causing swelling, stiffness and pain. Rotator cuff tears refer to a tear in one of the four tendons that blend together to attach to the humerus. These tendons transfer forces from the shoulder blade to the arm, providing motion and stability.
Fractures are also a shoulder injury concern. A shoulder fracture refers to a partial or total crack through one of the three bones of the shoulder. Fractures are usually the result of an impact injury. Clavicle (collarbone) fractures are usually treated conservatively, although there is a high incidence of non-union in distal third fractures. Patients with scapula (shoulder blade) fractures should be admitted and observed. Here, there is a concern of pulmonary complications. Fractures of the humerus are usually treated conservatively. Stiffness is often a concern for elderly patients. Therefore, early rehabilitation is usually necessary.
Certain signs indicate that patients should seek medical attention, including an inability to carry objects or use an arm; deformity of the shoulder joint; pain that occurs at night or while resting; pain that persists beyond a few days; an inability to raise the arm; or severe bruising or swelling around the joint.
Doctors often use a variety of methods to determine shoulder pain, including x-rays, MRIs (Figure 3), injections (Figure 4) and arthrograms. While shoulder pain can be treated conservatively, surgical intervention is sometimes required to alleviate shoulder pain.