Saddle joints
This joint looks like a horse’s back with a saddle resting on it. One bone is rounded (convex) and fits neatly into the other bone, which is concave. The saddle joint moves up and down and side to side, but it doesn’t rotate. Your wrist and your thumb have this kind of joint. See Figure 1-4 for an example of a saddle joint.
© John Wiley & Sons, Inc.
FIGURE 1-4: A saddle joint. The saddle joint moves up and down and side to side.
Ball-and-socket joints
This is truly a freewheeling joint — it’s ready for anything! Up, down, back, forth, or around in circles. The bone attached to a ball-and-socket joint can move in just about any direction. The end of one bone is round, like a ball, whereas the other bone has a neat little cave that the ball fits into. Your shoulders and hips have ball-and-socket joints. Swimming the backstroke is a perfect example of the kind of range of motion made possible by these joints. See Figure 1-5 for an example of a ball-and-socket joint.
© John Wiley & Sons, Inc.
FIGURE 1-5: A ball-and-socket joint. These joints can move just about any direction — up, down, back, forth, or around in circles.
Distinguishing Between Arthritis and Arthritis-Related Conditions
“True” arthritis
Arthritis as a “major player”
Arthritis as a “minor player”
Arthritis as a “companion condition”
In the following subsections, we go over the various types of arthritis and arthritis-related diseases and their classifications. We also discuss each disease in greater detail in Chapters 2, 3, 4 and 5. (Check out the sidebar titled “Hypersensitive fingers and toes” later in the chapter to find out about Raynaud’s phenomenon, a particularly chilling form of arthritis.)
Defining “true” arthritis
True arthritis isn’t a medical term; it’s just a convenient way of referring to the group of ailments in which arthritis is the primary disease process and is a major part of the syndrome. Osteoarthritis and rheumatoid arthritis are the best-known members of this group, which can cause problems ranging from mild joint pain to a permanently bowed spine.
The following include conditions in which arthritis is the major part of the syndrome and the primary disease process:
Ankylosing spondylitis (AS): A chronic inflammation of the spine, this disease can cause the vertebrae to grow together, making the spine rigid. Although the cause is unknown, heredity seems to be a factor.
Gout: This “regal” form of arthritis is caused by the build-up of a substance called uric acid, which forms sharp crystals that are deposited in the joint. These needlelike crystals cause inflammation leading to severe pain and are most commonly found in the knees, the wrists, and the “bunion” joint of the big toe. Genetic factors, conditions such as high blood pressure, kidney disease, and obesity, a diet high in animal purines, alcohol consumption, and certain drugs may cause gout.
Infectious arthritis: Bacteria, viruses, or fungi that enter the body can affect the joints, causing fever, inflammation, and loss of joint function.
Juvenile idiopathic arthritis (JIA): Formerly known as juvenile rheumatoid arthritis, this is a catchall term for the different kinds of arthritis that strike children under the age of 16. Pain or swelling in the shoulders, elbows, knees, ankles, or toes; chills; a reappearing fever; and sometimes a body rash are typical symptoms of various kinds of JIA. The cause is unknown.
Osteoarthritis (OA): In this, the most common type of arthritis, the cartilage breaks down, exposing bone ends and allowing them to rub together. The result can be pain, stiffness, loss of movement, and sometimes swelling. Osteoarthritis is most often found in the weight-bearing joints, such as the hips, knees, ankles, and spine, but it can also affect the fingers. It may be the result of trauma, metabolic conditions, obesity, heredity, or other factors.
Pseudogout: Like gout, pseudogout is caused by the deposition of crystals into the joint, but instead of uric acid crystals, they’re made from calcium pyrophosphate. Pain, swelling, and sometimes the destruction of cartilage can result.Note: This deposition of calcium pyrophosphate crystals is not related to the dietary intake of calcium.
Psoriatic arthritis: This form of arthritis occurs in people who have the autoimmune skin condition called psoriasis, which causes scaly, red, rough patches on the neck, elbows, and knees, as well as nail changes. Psoriatic arthritis can affect joints anywhere in the body, including the spine, the fingers, and the toes, which can swell up like little sausages.
Rheumatoid arthritis (RA): An autoimmune disease, RA causes the body to mistakenly attack its own joints, causing inflammation and swelling of the tissues surrounding the joint, resulting in joint pain and swelling. Over time, there can be a loss of cartilage, causing shrinkage of the space between the bone ends, which increases pain and decreases mobility; irreversible joint deformity can even occur. RA often affects the same joint on both sides of the body (for example, both wrists) and is two to three times more likely to strike women compared to men. (For more on this, see the sidebar “Why are Women More Likely to Get Arthritis,” near the end of the chapter.)
ARTHRITIS BY THE NUMBERS
Arthritis affects a surprisingly large number of us, as you can see by the following numbers:
Over 58 million adult Americans currently suffer from arthritis, or 1 in 4 of us. It is the leading cause of disability among adults in the U.S.
Women are more likely than men to get arthritis, which currently affects one in four women compared to one in five men. They are also far more likely to develop rheumatoid arthritis than men and to experience worse pain.
By 2040, it’s projected that that the number of U.S. adults with doctor-diagnosed arthritis will have increased by 49 percent to an estimated 78.4 million (nearly 26 percent of the population).
In 2013, the total national cost of treating arthritis was $140 billion. It is the reason behind more than 100 million outpatient visits and 6.6 million hospitalizations annually.
Osteoarthritis is by far the most common type of arthritis, affecting more than 30 million Americans,