1 in 6 adults in the U.S. has some form of the condition, but it is widely misunderstood.

By Rob Shmerling, Harvard Health Publications

Are your joints acting up because of the weather? Or is your body seeking revenge for the times when you cracked your knuckles as a kid? As comfortable as you might find these explanations for arthritis, clinical experience and research studies have yet to prove that these two myths, and a host of others, are true.

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Arthritis is common: One in six adults in the United States has some form of arthritis, and with the aging of our population, that fraction is going up. But the condition is also widely misunderstood. Unfortunately, just about every aspect of arthritis is clouded by uncertainty, misinformation and myth, including how to define it, what causes it, how to treat it and how to predict its course. And misunderstanding about the potential causes of arthritis can lead to bad decisions about treatment.

Read on to learn more about things that do not clearly cause arthritis, since this Top 10 List is not likely to appear on Letterman.

What Is Arthritis?

Strictly speaking, arthritis means inflammation of a joint, which often leads to some combination of pain, swelling, redness and limited motion. There are more than 100 types of arthritis. In some cases, the type of arthritis needs to be specifically defined, because successful treatment depends upon the correct diagnosis. Gout and rheumatoid arthritis are two such examples. Other types of arthritis can be grouped into categories because the prognoses and treatments are similar.

What Causes Arthritis?

While several types of arthritis have a known cause, the majority does not. Examples of common types of arthritis with no known cause include most cases of osteoarthritis and all cases of rheumatoid arthritis. Even when the cause is known (for example, uric-acid crystals cause gout when they deposit in the joint), it is generally not known why some people develop gout and others with the same risk factors do not. A joint infection may clearly be caused by a particular bacterium (as proven by detection of that bacterium in the joint fluid), but that doesn’t tell you why the bacterial infection developed in the first place. An injury such as a broken bone or torn cartilage may lead to arthritis years later, but not everyone with a similar injury will get arthritis. For most cases, then, arthritis develops for no known reason.


What Does Not Cause Arthritis?

When the cause of an arthritic condition has not yet been discovered, it may be difficult or even impossible to disprove a theory, even one that is improbable. Here are some of the most common, but as yet unproven, theories about the cause of arthritis:

1. Overuse

With usual use, joints hold up well most of the time. Some people who are on their feet all day assume that knee or hip arthritis must be related; yet it clearly doesn’t explain the same type of arthritis occurring in the hands. Conversely, if arthritis is caused by overuse, right-handed persons should have more arthritis in the right hand; yet, that is not the case. Another compelling example is that marathoners and other runners appear to have no increased risk of arthritis. There are exceptions, of course: Jack-hammer operators and athletes, for instance, may develop degenerative arthritis because of repeated joint injury.

2. The weather or a damp, cold breeze

This notion probably follows from the rather common experience of arthritis sufferers that the weather seems to affect their joint symptoms. Although my patients often describe the ability to predict weather (“better than a weatherman”), how reliably it occurs or why it happens is not certain. For example, even if a person’s joints ache more every time it is cold and damp, that does not mean the weather caused the arthritis in the first place. At the current time, there is no evidence that identifies any type of weather as a cause of any type of arthritis. Similarly, despite the testimonials of individual people, it is unlikely that sitting near an open window can cause arthritis, even if there is a cold draft.

3. Most medications

Although there are occasional exceptions, prescription, over-the-counter and complementary and alternative medications are not a recognized cause of arthritis. Again, there are rare exceptions: Corticosteroids, including ones available in pill form (such as prednisone) may cause interruption of the blood supply to the bones around the hip, causing death of the bone there (called avascular, or aseptic, necrosis). If the “ball” of the ball-and-socket joint loses its round shape due to avascular necrosis, arthritis may develop. Other drugs (such as alendronate or phenobarbital) may cause bone or joint pain but not arthritis. Similarly, diuretic drugs (“water pills”) may increase the risk of gout, but it isn’t the cause of the disease. Finally, a rare condition called “drug-induced lupus” can follow treatment with the certain medications including procainamide and hydralazine; arthritis may be a part of the reaction.

4. Infections and vaccinations

Most infections, whether due to a virus, bacterium or other organism, will not cause arthritis, and most cases of arthritis are not caused by infection (at least as far as we know). There are infectious causes of arthritis, but they represent a small fraction of all arthritis. Important examples include bacteria (such as Gonorrhea and Staphylococcus), Lyme disease, some viruses (including occasional cases of hepatitis B, hepatitis C or parvovirus). Similarly, vaccinations, including those for Lyme disease and rubella, have been linked in rare cases to the development of arthritis, but the connection to a vaccination has been unclear. Some rubella vaccines contained strains of the virus that seemed to cause arthritis more often; these vaccines were removed from the market and reports of vaccine-associated arthritis are less frequent now. The Lyme vaccine also has been withdrawn from the market, though due to poor sales, not because of side effects. Fortunately, the vast majority of people receiving the most common vaccinations never develop arthritis.

5. The wrong diet

Theories about which diet is best to prevent or treat arthritis have been around for centuries, but with rare exception and some common sense, diet does not seem to play a crucial role in arthritis. First, the exceptions: Some people find that particular foods (or alcoholic beverages) trigger attacks of gout. Secondly, there is an association between obesity and osteoarthritis, so a diet that promotes weight loss may be helpful. And in some cases, inadequate calcium or vitamin D may contribute to osteoporosis; if a fracture occurs as a result, arthritis may eventually follow. However, our current understanding of most types of arthritis comes with no strong recommendation about which foods to choose and which to avoid. It is worth emphasizing that vegetarian diets or those that avoid “nightshade” vegetables (including potatoes, tomatoes, green peppers and eggplant) are not only unproven as arthritis treatment, but there is also no compelling evidence supporting a particular food or food group as a cause of arthritis. Undoubtedly, future research will provide useful information regarding the importance of diet as a cause or treatment of arthritis.

6. Cracking knuckles

Although you can injure a joint by overenthusiastic knuckle cracking, there is rather convincing evidence that regular knuckle cracking has little effect on joint health.

7. Getting older

Although degenerative joint disease (also called osteoarthritis) becomes more common with age, arthritis is not inevitable. Therefore, age alone cannot be blamed as “the cause” of arthritis.

8. Mental or emotional stress

Although there are stories of people having severe emotional trauma and soon after developing an arthritic illness, there is no convincing evidence that psychological stress causes any recognized type of arthritis. On the other hand, stress can make any pain seem worse, and there is controversy regarding the relative importance of psychological stress on the development or perpetuation of joint pain without arthritis (as in fibromyalgia).

9. Poor posture

“Slouching” does not cause arthritis, although certain types of arthritis or bone diseases can affect posture. The idea that poor posture causes arthritis probably follows a misunderstanding of cause and effect: Osteoporosis may cause a stooped posture because vertebrae collapse (called compression fractures). Arthritis in the spine may follow, but the stooped posture is not the cause of the arthritis. Another example of arthritis affecting posture (rather than the other way around) is ankylosing spondylitis, a condition in which inflammation of joints in the lower spine leads to a rigid spine (ankylosis means fusion). However, “poor posture” itself does not lead to arthritis.

10. Inadequate calcium intake

Recommendations to take extra calcium follow the observation that without enough calcium, bones may become thin and so weak that fracture becomes more likely. That’s what osteoporosis is but osteoporosis is not arthritis, and calcium intake has rather little to do with the development of arthritis (unless, as described above, osteoporosis leads to fracture and fracture leads to arthritis).

The Bottom Line

With so many types of arthritis and so little understanding about their causes, it is understandable why many myths about arthritis circulate. In fact, it may be tempting to latch on to even a far-fetched theory about cause rather than accept the explanation that “nobody knows.” But if faulty assumptions about the cause of your arthritis lead you to adopt a difficult or unhealthy diet, or to move to a different climate, or to pursue another costly or risky treatment, you may be sorely disappointed and even less healthy than when you started.

Additional research may force me to remove one or more of the items on my Top 10 list. For now, however, the most direct and honest answer most health-care providers can offer is that we simply don’t know why most cases of arthritis develop. Until better answers are available, my advice for some of the most common types of arthritis is to dwell less on why it happens and to focus more on how to get better.

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