How Arthritis Works

arthritic hands
Arthritis can make daily tasks difficult -- and it hurts like the dickens.
© iStockphoto/rustycloud

Many of us think of arthritis as a condition that causes old people to rub their hands together and predict changes in the weather. That's not entirely the case. In fact, there are some truths about arthritis that may surprise you. For starters, arthritis isn't just one disease -- there are more than 100 types of arthritis. More than 350 million people worldwide have arthritis, as nearly one in five Americans [source: Shiel]. And it affects younger people, too -- six out of 10 arthritis sufferers are under 65 years old [source: CNN].

So, what exactly is arthritis? Arthritis is swelling in one or more of your joints that causes pain and stiffness and can lead to destruction of tissue in the joint. In some cases, a joint can become so damaged that it needs to be replaced, as is often the case with osteoarthritis (an age-related form of arthritis) and hip joints.


There are different causes of this inflammation, which we'll discuss throughout this article. Arthritis can be caused by genetics, an old ski injury or your own immune system. You may first experience discomfort late in life, or you could be diagnosed when you're just a teenager.

Joint pain touches every part of a person's life. Not only do your activity levels plummet, you end up spending more and more time just managing pain. Physical abilities are curbed and independence can be compromised or even entirely lost.

There are many therapies and drugs available for the treatment of arthritis, and arthritis research continues to turn up new treatment options. As our understanding of arthritis grows, we'll be better able to recognize its early symptoms, seek out the right kind of help and retain -- or reclaim -- as much of our pre-arthritic lives as possible.



Arthritis and Your Joints: What Can Go Wrong

Bones have several important purposes in our bodies. Besides producing blood in the marrow, bones provide a rigid support system for the rest of the body and allow you to move. While bones themselves are sturdy, durable and immobile, the places where bone connects to bone -- the joints -- enable us to perform a wide variety of movements. There are six different types of joints, such as the ball-and-socket joint in your hip and the hinge joint that is your elbow.

Bones are held together with various types of connective tissue such as cartilage (protein-based material that cushions the bone ends), tendons (which connect muscle to bone) and ligaments (which connect bone to bone). This tissue holds the joint together and provides stability while enabling a range of motion. Cartilage covering the bone ends prevents them from rubbing together. Surrounding the joint is a joint cavity, a sac lined with a membrane called the synovium. The synovium produces synovial fluid that nourishes the joint and cartilage.


Sturdy and well designed as these joints are, they aren't immune to damage and decay. The knee joint, for example, has an intricate design that allows for complicated maneuvering. Bone ends must be shaped just right, cartilage and tendons must be properly oriented and the trochlear groove must be perfectly aligned with the kneecap that slides back and forth in it. If you take out random amounts of bone, remove a little cartilage and swell everything else up, everything in the knee can get off track. If it stays even slightly off track for too long, the impaired motion will start grinding bones together, pinching connective tissue or wearing away tendons as they slide against bones they weren't designed to slide against.

Different types of arthritis may affect some joints more than others. Psoriatic arthritis tends primarily to affect the hands and feet, the shoulder is more susceptible to injury-related arthritis, and osteoarthritis most often affects the hands, hips, knees and spine.

In the early stages of arthritis, you might not even feel any pain. As the damage increases, symptoms such as discomfort, tightness or a feeling of heat in the joint will appear and then worsen. If any of your joints begin feeling stiff, tender or like they're grating together, contact a doctor. The earlier arthritis is diagnosed, the better your options and chances for treating it.


Osteoarthritis, the Most Likely to Strike

inflamed knee
When your cartilage deteriorates and the bones start rubbing up against one another, it's not quite as cozy as it sounds.
© iStockphoto/Eraxion

Osteoarthritis (OA) -- also known as degenerative arthritis -- is the loss of joint cartilage, usually caused by age-related wear and tear. OA can also be caused by a previous trauma to the joint, such as a sports injury. This form of arthritis is the most common, and it affects about one out of every 15 people in the United States alone [source: Shiel].

The cartilage on the ends of your bones is made up of protein and serves as a shock absorber for the joint. As the years go by, more and more water ends up in the cartilage, slowly breaking down the protein. Soon, pieces of cartilage peel away, leaving small notches. As you continue using the joint, the damage increases. Left unchecked, OA will wear away all of the cartilage, meaning the two bone ends in a joint will rub against each other.


In severe cases of OA, you and your orthopedic surgeon may decide to replace the entire damaged joint (most commonly the knee or the hip). Hip replacements have a faster recovery time and a better long-term success rate because the hip's ball-and-socket joint is relatively simple and stable in design. Surgeons are doing great things with knees these days as well, but it's a much trickier joint to duplicate artificially and the replacement itself usually needs to be replaced after 10 or 15 years.

Sometimes cartilage breakdown will stimulate the bone to produce bony outgrowths known as spurs. These alone don't cause problems, but if they make contact with other bones or nerves, you're going to know about it. Spurs can develop pretty much anywhere, from your fingers (making them look disfigured or gnarled) to your spine, knees or neck. Sometimes these spurs will break loose and get embedded in the synovium that lines the joint. They can also lodge between a joint's two bones, preventing movement. The floating spur may slip back out of the way, allowing movement again, but continue floating back in and out of the joint, causing you ongoing discomfort. If spurs are causing you trouble, they can usually be removed, depending on their location. If they aren't causing you discomfort or mobility issues, spurs can be left alone.

Next, we'll learn about another form of arthritis: rheumatoid arthritis.


Rheumatoid Arthritis: One Size Doesn't Fit All

hands with rheumatoid arthritis
When rheumatoid arthritis affects the hands, it can change their appearance.
© iStockphoto/StanRohrer

About 1.3 million Americans suffer from rheumatoid arthritis (RA), a condition caused by the immune system attacking the body's own joint tissue. There is currently no cure, although it can be treated. RA, like other forms of arthritis, causes inflammation of the joints. However, it commonly affects the joints on both sides of the body -- if your right knee is affected, your left knee will be, too. RA often causes swelling in the hands and wrists, though other joints throughout the body are susceptible to it as well.

But it's not just about joint pain -- RA can actually make you feel tired and sick. Some people get a fever, others deal with "cotton mouth," and some even suffer from anemia. This wide variation in symptoms can make it difficult to diagnose RA, especially in its earlier stages.


Doctors can test for a specific antibody, known as rheumatoid factor, that often accompanies RA, but it isn't a surefire approach: Some people will test positive for rheumatoid factor without ever developing RA, while others will test negative even though their joints are under attack as a result of the condition.

This type of arthritis affects different people in different ways. Some people may only briefly experience symptoms without any lasting damage, never to be bothered again. Others may experience periodic bouts, in which it flares up for a few weeks or months and then goes into remission, only to reappear later. For others, RA shows up and never leaves.

RA is an autoimmune disease. The cause of inflammation is malfunctioning white blood cells, which normally protect us from bacteria and infection. Nobody knows why, but sometimes these cells travel toward a joint and, believing there's a threat, flood into the area. The synovium becomes inflamed, puffy, much thicker than usual and warm to the touch. The cells of the synovium then begin to wear away at the nearby bone and cartilage, ultimately causing serious damage.

Genes seem to have some role in determining a person's susceptibility to RA, but scientists believe many factors play a role, including viral or bacterial infection as well as hormonal fluctuations. Women are affected much more often than men by RA -- two to three times more often, in fact.

Researchers have discovered that most of the damage occurs in the first three years of RA. This makes it important to bring any joint pain to your doctor's attention immediately. Its symptoms normally appear in middle age or later, but they can also show up as early as childhood.


Juvenile Arthritis and Gout: Not Growing Pains

Periodic aching in children's bones isn't unusual and is normally the result of "growing pains." However, for about a quarter of a million children in the United States who experience lasting joint pain, the culprit is juvenile arthritis (JA). Nobody knows what causes juvenile arthritis, but environmental factors or possession of a certain gene may be to blame. It's a chronic condition resulting from the body's immune system acting against the body. JA can appear and then go into long periods of remission, never to cause problems again. In other cases, it will continue to damage joints and significantly alter the child's lifestyle and mobility.

Sometimes an organ becomes swollen or a rash develops around the affected joint area. Children with JA frequently show symptoms in the morning that gradually improve as the day advances. Because children's joints grow and develop quickly, an arthritic joint may become misaligned or misshapen. Any suspicions or worries about a possible case of JA should be brought immediately to the attention of the family physician. If JA is confirmed, a pediatric rheumatologist will be able to begin treating the child with NSAIDs, nighttime splinting or biologics (which we'll learn more about later).


Gout is another type of arthritis that sometimes seems to appear out of nowhere. Attacks of gout often occur at night and cause intense pain in the big toe, hands, wrists, feet or ankles, making the joint visibly swollen and red. The pain may last a week or so and then go away as suddenly as it appeared.

Gout is caused by an overload of uric acid. Your body produces uric acid to break down substances known as purines that your body produces naturally. Purines are also derived from organ meats, herring and anchovies. (If your family refuses to eat the pizza toppings you prefer, you may be at risk.) The kidneys normally take care of uric acid, but sometimes they can't handle the workload. When too much uric acid builds up in your blood, crystals can form in your joints and start making trouble. Left untreated, gout will eventually damage your affected joints.

Excessive alcohol use, high blood pressure and heredity increase the risk of gout. It can be treated with NSAIDs, steroids, colchicine (a drug that limits inflammation caused by gout) and allopurinol, a drug that helps prevent purines from becoming uric acid in the first place.


Nonsurgical Arthritis Treatment, from Aspirin to Acupuncture

A doctor applies herbal medicine to a patient's back at a traditional Chinese medicine clinic in Beijing.
A doctor applies herbal medicine to a patient's back at a traditional Chinese medicine clinic in Beijing. 
Cui Hao/ChinaFotoPress/Getty Images

Fortunately for those suffering from arthritis, there are treatments available that can ease pain, swelling and discomfort as well as limit damage to the joints. One readily available treatment won't require a trip to the doctor: good old-fashioned weight loss. Through diet and exercise, you can shed excess pounds that add stress and strain to already overstressed joints.

Eat a well-balanced diet, rich in fruits, vegetables and "good" fats (monounsaturated and polyunsaturated fats, as found in nuts, fish, canola oil and sunflower oil). Vitamin C -- readily available in orange juice -- has been shown to slow the progression of osteoarthritis, while vitamin D is important for bone strength. Omega-3 fatty acids help suppress inflammation and can be found in various fish, as well as tofu and flaxseed.


When you go for a workout, avoid strenuous or jarring activities that may exacerbate pain. Stretch and warm up before exercising, and stretch and cool down when you're done. Give yourself plenty of time to rest and don't push yourself too hard, but try to get regular amounts of light to moderate exercise. Swimming is one activity that is both easy on the joints and a great cardiovascular workout.

As far as treatment goes, there are over-the-counter products that can help with arthritis pain. Topical applications (gels) can produce hot or cold sensations that can diminish your awareness of discomfort. Topical analgesics (or "pain rubs") can provide relief by allowing your skin to absorb salicylates, also found in aspirin. Cold packs and paraffin wax dips might help you feel better, too.

Nonsteroidal anti-inflammatory drugs (NSAIDs) reduce inflammation by lowering the level of prostaglandins (which are similar to hormones and cause inflammation) in the body. NSAIDS, which include aspirin and ibuprofen, are commonly used to treat arthritis, and they were long viewed as the first treatment option that should be explored. However, rheumatoid arthritis does most of its damage to your joints in the first three years or so. Doctors now prefer to use more powerful drugs early on, to prevent or limit the first large wave of damage. Disease-modifying antirheumatic drugs (DMARDs ) -- which include methotrexate, gold and sulfasalazine -- actually change the way your immune system works, suppressing it in a way that still isn't fully understood. DMARDs can greatly reduce the amount of joint damage caused by certain forms of arthritis, most notably rheumatoid arthritis.

Arthritis pre-dates modern medicine, of course, and so do many of its treatments, such as meditation, acupuncture and fasting to remove impurities. Some patients swear by chiropractic treatment, while others seek out nutritional supplements, like glucosamine and chondroitin, to relieve discomfort. Many modern medical treatments, such as DMARDs, involve processes that aren't fully understood, and so do "alternative" treatments. People suffering from arthritis should talk to a wide range of medical specialists to find a treatment option that is right for them.

We'll discuss surgical treatments in the next section.


Surgical Arthritis Treatments: Time for the Operating Room

X-ray of hip replacement
Your X-ray after a hip replacement might look a little something like this.
© iStockphoto/33karen33

Sometimes standard treatments aren't effective for people with arthritis. For these cases, there are surgical options to aid in pain relief and mobility and to correct joint disfigurement or deterioration.

In some cases, arthroscopy -- cutting out damaged tissue and debris from your joint through a small incision -- may provide a great deal of somewhat temporary relief. (Rheumatoid arthritis, unfortunately, can't be cured through this or any other procedure.) Arthroscopy is a relatively minor procedure, and it allows surgeons to smooth out rough joint surfaces and clean out bits and pieces of tissue or foreign matter that are floating around in the joint. Likewise, a synovectomy allows surgeons to cut out and remove portions of the joint's inflamed synovium that aren't responding to DMARDs.


There are a number of operations that can be performed on the hands and fingers. Surgeons can repair or reattach damaged tendons, or they can cut them in order to allow greater range of motion. Ligaments in the hand can also be cut (as they are in carpal tunnel procedures) if the ligament is squeezing a nerve along the middle of the wrist. Joints in the fingers may be capped with plastic or metal components or can be fused entirely together to provide relief (with the disadvantage of diminished mobility).

The vertebrae can also be connected through bone grafts or man-made connective materials. Once held in place, new bone grows, stabilizes and strengthens the fused bones. Surprising as it may seem, many people with fused vertebrae don't lose any flexibility or range of motion in their backs.

Cases in which bones and cartilage have undergone great damage may call for total joint replacement. Knees, hips, fingers, thumbs, shoulders and ankles are among the joints that can be removed and replaced by artificial implants. The implants may be screwed onto the bone end or attached with a special type of cement. Joint replacements come with their own share of problems -- sometimes the new joints must be removed if they don't fit correctly or if an infection develops. In many cases, though, patients with artificial transplants feel a great deal of relief from what had often been constant agony.

In cases of deformity caused by constant inflammation, doctors will attempt to correct the problem using nonsurgical splints. If that doesn't work, the joint can be surgically realigned.


New Hopes for Treating Arthritis

There have been many advances in the treatment of arthritis in recent years. One of those advancements is the use of biologic response modifiers, also known as biologics. Biologics are proteins taken from human genes and altered to target and change certain elements of the immune system (unlike DMARDs, which work broadly on the immune system). Biologics have shown very good results in the treatment of RA and other forms of arthritis, greatly reducing symptoms and slowing the actual progression of the disease. Most patients who respond to them enter a state of arthritic remission. Biologics are either injected or taken intravenously. Since they suppress the immune system, there is an increased risk of infection.

Currently, cartilage cells can be collected from other parts of the body and transplanted to the damaged area, but the cells often don't produce enough new cartilage. Researchers are making great strides toward using bone stem cells to reproduce and replace damaged cartilage in patients with OA. The stem cells are located within the articular cartilage and can transform into chondrocytes, which form cartilage.


Doctors sometimes use platelet-rich plasma (PRP) grafts to stimulate tissue growth and repair. Platelets -- the portion of blood that forms clots -- contain many elements that stimulate growth. Blood is taken from a patient and spun in a centrifuge until the platelets are separated. This platelet-rich plasma is then injected back into the patient using diagnostic ultrasound to precisely locate the target area. It is an outpatient procedure, and more than one treatment may be necessary to obtain positive results.

To learn more about arthritis, protecting your joints and knee replacements, try the HowStuffWorks articles on the next page.


Lots More Information

Related HowStuffWorks Articles

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  • Arthritis Foundation. "Diet and Your Arthritis." (April 8, 2009)
  • Fortin, Judy. "It's not just an old people thing: Arthritis myths debunked." Jan. 26, 2009.
  • Groch, Judith. "Biologics in Rheumatoid Arthritis Linked to Skin Cancer Only." MedPage Today. Aug. 29, 2007.
  • Henderson, Brian. Arthritis Today. "White blood cells and warning bells." April, 2000.
  • Johns Hopkins University. "Rheumatoid Arthritis Treatment." (March 29, 2009)
  • Kidzworld. "Cracking Down on Knuckles." (April 4, 2009)
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