Gliding joints
A gliding joint contains two bones with somewhat flat surfaces that can slide over each other. The vertebrae in your spine are connected by gliding joints, allowing you to bend forward to touch your toes and backward to do a backbend (well, maybe!). See Figure 1-2 for an example of a gliding joint.
Hinge joints
You can find hinge joints in your elbows, knees, and fingers. These joints open and close like a door. But just like a door, hinge joints only go one way — you can’t bend your knee up toward your face, only back toward your rear. See Figure 1-3 for an example of a hinge joint.
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FIGURE 1-2: A gliding joint. The gliding joint helps keep your vertebrae aligned when you bend and stretch.
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FIGURE 1-3: A hinge joint. Hinge joints bend only one way.
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.
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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.
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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
