Submitted by McLean County Orthopedics
The shoulder is the most movable joint in the body, which also makes it one of the most potentially unstable joints. As a result, it is the site of many common problems including sprains, strains, dislocations, separations, tendinitis, bursitis, torn rotator cuffs, frozen shoulder, fractures, and arthritis. To better understand shoulder problems and how they occur, it helps to begin with a brief explanation of the shoulder’s structure and how it functions.
The shoulder joint is composed of three bones: the collarbone (clavicle), the shoulder blade (scapula), and the upper arm bone (humerus). Two joints facilitate shoulder movement and allow it to move forward and backward, up and down, as well as in a circular motion.
In contrast to the hip joint, which more closely approximates a true ball-and-socket joint, the shoulder joint can be compared to a golf ball and tee, in which the ball can easily slip off the flat tee. Because the bones provide little inherent stability to the shoulder joint, it is highly dependent on surrounding soft tissues such as capsule ligaments and the muscles surrounding the rotator cuff to hold the ball in place. Whereas the hip joint is inherently quite stable because of the encircling bony anatomy, it also is relatively immobile. The shoulder, on the other hand, is relatively unstable but highly mobile, allowing an individual to place the hand in numerous positions. It is, in fact, one of the most mobile joints in the human body.
The bones of the shoulder are held in place by muscles, tendons, and ligaments. Tendons are tough cords of tissue that attach the shoulder muscles to bone and assist the muscles in moving the shoulder. Ligaments attach shoulder bones to each other, providing stability. The rotator cuff is a structure composed of tendons that work along with associated muscles to hold the ball at the top of the upper arm in the socket and provide mobility and strength to the shoulder joint. Two filmy sac-like structures called bursae permit smooth gliding between bones, muscles, and tendons. They cushion and protect the rotator cuff from the bony arch of the acromion.
The shoulder is easily injured because the ball of the upper arm is larger than the shoulder socket that holds it. Although the shoulder is easily injured during sporting activities and manual labor, the primary source of shoulder problems appears to be the natural age-related degeneration of the surrounding soft tissues such as those found in the rotator cuff. The incidence of rotator cuff problems rises dramatically as a function of age and is generally seen among individuals who are more than 60 years old. Often, the dominant and nondominant arm will be affected to a similar degree. Overuse of the shoulder can lead to more rapid age-related deterioration.
As with any medical issue, a shoulder problem is generally diagnosed using a three-part process.
- Medical history. The patient tells the doctor about any injury or other condition that might be causing the pain.
- Physical examination. The doctor examines the patient to feel for injury and to discover the limits of movement, location of pain, and extent of joint instability.
- Tests. The doctor may order one or more of the tests listed below to make a specific diagnosis. These tests may include the following:
- Standard x-ray. An x-ray is useful for diagnosing fractures or other problems of the bones. Soft tissues, such as muscles and tendons, do not show up on x-rays.
- Arthrogram. A 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.
- Ultrasound. A noninvasive, patient-friendly procedure in which a small, hand-held scanner is placed on the skin of the shoulder. Just as ultrasound waves can be used to visualize the fetus during pregnancy, they can also be reflected off the rotator cuff and other structures to form a high-quality image of them. The accuracy of ultrasound for the rotator cuff is particularly high.
- MRI (magnetic resonance imaging). A noninvasive procedure in which a machine with a strong magnet passes a force through the body to produce a series of cross-sectional images of the shoulder.
There are other diagnostic tests that may be used if your physician determines that it is necessary to make an accurate diagnosis.
Next month’s article will address some specific shoulder problems along with treatment options.
For more information on any orthopedic problem, call 309-663-6461 to schedule an appointment with the board-certified physicians at McLean County Orthopedics, or visit their website at www.mcleancountyorthopedics.com. Their new office is located at 1111 Trinity Lane in Bloomington.