Overview
Arthritis is a disease characterized by deterioration and inflammation in the joints. There are about 100 different types of arthritis, affecting about 40 million Americans. Osteoarthritis (OA) is the most common kind, affecting about 20 million people. Rheumatoid arthritis is another common form.
OA is a "wear and tear" disease and becomes more common as people get older; indeed, most people develop the condition to some degree in at least one joint by age 60. Bones that meet at joints have soft caps of cartilage at the ends, and years of bending and rubbing can start to wear these caps down. Fingers, knees, and hips are most often affected. The frequency of OA starts to rise after age 50 among men,, and after age 40 among women, and symptoms tend to get more severe as people age. Those symptoms can range from mild stiffness to severe pain.
Fortunately, doctors have found that programs of exercise and physical therapy can make a big difference in easing any discomfort. So can judicious use of painkillers such as acetaminophen and use of anti-inflammatory drugs. For the most severe cases, joint replacement surgery is often recommended; these operations offer patients major improvements in their quality of life. Finally, people who take an active role in managing their disease can lead long and active lives.
Need-to-know anatomy
The joints in the body, where two bones come together and need to flex, are designed to make movement easy. The whole joint area is surrounded by a thin covering called the synovial membrane, which releases a lubricating fluid into the joint. The ends of the bones in the joint are lined with slippery cartilage. The whole structure is held together with muscles, tendons, and ligaments. OA can damage any or all of these crucial parts.
Symptoms start when the protective cartilage stiffens and starts to wear away, often on one side of the joint. As the space in the joint narrows, more cartilage starts rubbing together and eroding. Bits of cartilage fill the joint area, irritating the surrounding membrane, and the tendons and ligaments stretch painfully. Knobs of bone, called spurs, begin to grow. All this means that the joint begins to grind whenever it moves.
Causes
The most common form, called "primary" OA, is the gradual breakdown of cartilage covering the ends of bones, mostly due to prolonged stress on the joint. Often this is attributed to age, but age is not the only reason. Cartilage in OA patients has an abundance of enzymes that break it down, regardless of age.
Another form, called "secondary" OA, is a result of trauma to the tissues surrounding the joint. It can show up at younger ages than primary OA. For example, people who have jobs that require repeated bending and strain often get OA in the knee. High school football players who get knee or hip injuries can also develop OA. Secondary OA has not, however, been reliably linked to physical exercise, even jogging.
Risk factors
Doctors have identified several major risk factors for developing OA:
Family history:
People with close relatives who have OA tend to be prone to the disease themselves. A defect in the gene responsible for the formation of collagen, a component of cartilage, makes people more susceptible.
Advancing age:
The older people get, the more frequently OA symptoms appear.
Obesity:
Carrying too much weight puts extra stress on certain joints, such as the hips and the knees.
Overuse or injury to the joint:
Athletes and those whose jobs require repetitive bending, say, may be at higher risk.
"Malaligned" bones:
Conditions such as having knock-knee or being bowlegged increase the chances for wear and tear in the joint.
Having another form of arthritis, such as rheumatoid arthritis:
This can traumatize a joint, also increasing the chances of wear and erosion.
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