According to the American Academy of Orthopaedic Surgeons, over 4 million people in the United States seek medical care each year for shoulder problems. Each year, shoulder problems account for over 1.5 million visits to orthopaedic surgeons. Common shoulder problems include:
What Are the Structures of the Shoulder and How Does the Shoulder Function?
The shoulder joint is composed of three bones:
Two joints facilitate shoulder movement. The acromioclavicular (AC) joint is located between the acromion (part of the scapula that forms the highest point of the shoulder) and the clavicle. The glenohumeral joint, commonly called the shoulder joint, is a ball-and-socket type joint that helps move the shoulder forward and backward and allows the arm to rotate in a circular fashion or hinge out and up away from the body.
The capsule is a soft tissue envelope that encircles the glenohumeral joint. It is lined by a thin, smooth synovial membrane.
The bones of the shoulder are held in place by muscles, tendons, and ligaments.
The rotator cuff is a structure composed of tendons that, with associated muscles, holds the ball at the top of the humerus in the glenoid socket and provides mobility and strength to the shoulder joint.
Two filmy sac-like structures called bursae permit smooth gliding between bone, muscle, and tendon. They cushion and protect the rotator cuff from the bony arch of the acromion.
What Are the Origin and Causes of Shoulder Problems?
The shoulder is the most movable joint in the body. However, it is an unstable joint because of the range of motion allowed. It is easily subject to injury because the ball of the upper arm is larger than the shoulder socket that holds it. To remain stable, the shoulder must be anchored by its muscles, tendons, and ligaments.
Shoulder pain may be localized or may be referred to areas around the shoulder or down the arm. Disease within the body (such as gallbladder, liver, or heart disease, or disease of the cervical spine of the neck) also may generate pain that travels along nerves to the shoulder.
How Are Shoulder Problems Diagnosed?
Following are some of the ways doctors diagnose shoulder problems:
- Medical history (the patient tells the doctor about an injury or other condition that might be causing the pain).
- Physical examination to feel for injury and discover the limits of movement, location of pain, and extent of joint instability.
- Tests to confirm the diagnosis of certain conditions. Some of these tests include:
- x ray
- arthrogram - Diagnostic record that can be seen on an x ray after injection of a contrast fluid into the shoulder joint to outline structures such as the rotator cuff. In disease or injury, this contrast fluid may either leak into an area where it does not belong, indicating a tear or opening, or be blocked from entering an area where there normally is an opening.
- MRI (magnetic resonance imaging) - A non-invasive procedure in which a machine produces a series of cross-sectional images of the shoulder.
Other diagnostic tests, such as injection of an anesthetic into and around the shoulder joint, are discussed in specific sections of this guide.