Arthritis Basics

What is arthritis?

Arthritis is a painful condition that affects one or more joints. More than 100 conditions may be classified as arthritis.

Most forms of arthritis are degenerative or rheumatic conditions, meaning they involve some sort of inflammation, usually of the soft tissue (cartilage) or membranes surrounding the body’s joints. Other arthritic conditions may primarily involve inflammation of supporting structures, such as muscles, ligaments or tendons. In time, the inflammation may also cause swelling, redness and difficulty moving the joints.

Arthritis comes from the Greek words for joint inflammation. However, the most common arthritic condition, osteoarthritis, involves degeneration of cartilage at the joints, but usually not inflammation.

Arthritis occurs primarily in the joints. In human anatomy, a joint is where two or more bones meet. There are several types of joints. Some joints do not move very much or at all, such as where bones in the skull meet. Arthritis occurs mostly in cartilaginous and synovial joints, such as those in the knees, hips, hands and feet, which can move.

The cartilaginous and synovial joints are formed by the juncture of bones and their surrounding ligaments. The space enclosed by the ligaments and adjoining bones forms a cavity called the joint capsule. The outer layer of the capsule is formed by a fibrous membrane that may include the ligament. The inside of the capsule is lined with synovial membrane (synovium). This membrane secretes synovial fluid, which fills the joint capsule and provides lubrication. The ends of the bones encased in the capsule are cushioned in soft cartilage. The cartilage and synovial fluid permit the bones to move without rubbing against each other.

Cartilaginous joints do not have a synovial cavity but have cartilage and fibrous discs between the bones to allow some movement. The vertebrae in the spine have cartilaginous joints.

Joints affected by arthritis do not function smoothly. In some cases, the cartilage degenerates and irritates the bones. Small bony outgrowths form, swelling the bone and decreasing the space within the joint capsule. In other cases, the synovial membranes or cartilage become inflamed and swell. As a result, the joint may swell and become painful to use. Regardless of the origin (degeneration or inflammation), joints can become stiff, painful and swollen, eventually impairing their function.

Some forms of arthritis also affect other parts of the body, such as the skin, urinary tract, eyes or heart.

Arthritis develops in many ways. Osteoarthritis, the most common form, usually develops with age. Years of weight and repetitive stress on the joints cause the cartilage to degenerate. Sudden trauma to a joint, such as from a sports injury, can ultimately lead to osteoarthritis. Other forms of arthritis develop at any age (even among children) as the result of causes including infection, such as Lyme disease, or as an autoimmune disorder, such as rheumatoid arthritis (RA), where the body mistakenly attacks its own tissues.

Some people experience arthritis as stiffness in a hip or knee joint. For others, the pain may start in one joint and spread to others and include stiffness, swelling and redness. In some cases, arthritis causes stiffness upon rising in the morning. For other people, the pain worsens after they use the affected joint, such as during exercise. All these symptoms vary depending upon the kind of arthritis.

Arthritis can be debilitating. Many of the mobility problems elderly people experience are the result of osteoarthritis. RA, which can begin at any age, may swell and damage joints enough to cause deformity. Although there are ways to stop or delay the progression of many forms of arthritis, there is generally no cure. Treatment focuses on controlling pain, increasing the mobility of the joint, halting progression of the disease and improving quality of life.

About 46.4 million Americans, including 294,000 children, had physician-diagnosed arthritis in 2003, the U.S. Centers for Disease Control and Prevention (CDC) estimated in 2007. That's a 25 percent increase from 1997, due largely to the aging of the population, Arthritis is the nation's leading cause of disability and in 2003 cost $128 billion in medical expenses and lost productivity, the CDC says .

Types and differences of arthritis

More than 100 conditions can be classified as arthritis, including:

Osteoarthritis (OA)

The most common form of arthritis, usually seen among older people. OA affects only the joints, not any other systems in the body. The cartilage wears away or breaks down. The lack of cartilage and new growth of exposed bones (bone spurs) causes the bones to rub together. OA occurs most often in the knees, hips and spine, which bear much of the body's weight. It is also common in the hands and feet.

Trauma can also trigger OA. For example, an athletic injury that damages a meniscus (cartilage pad) may lead to OA in the knee.

Rheumatoid arthritis (RA)

Affects the membranes in the joint capsules and may attack other tissues and organs as well. RA inflames the synovial membranes (which cushion the joints) and causes joint swelling, pain and sometimes deformity. It is an autoimmune disorder, in which the body’s immune system attacks its own tissues.

RA usually occurs symmetrically (e.g., in both hands or both feet). RA inflammation may affect other body systems, such as the cardiac system, where it can be life-threatening. RA is much more common in women than in men. RA has periods of flare-ups followed by periods of remission.

Juvenile arthritis

Several forms of arthritis occur in children. The most common is juvenile rheumatoid arthritis (JRA), which can affect one joint or many joints. JRA attacks the membranes of the joint capsules. About half of the children with JRA have it in four or fewer joints.

For some children, JRA extends into adult life. Other children actually have adult RA that begins at an early age. The development of systemic JRA later in life is known as adult-onset Still’s disease.

Gout and pseudogout

Involve crystal deposits in one or more joints. In gout, an excess of uric acid builds up in a joint (often the big toe) causing pain. Gout can also be caused by an underexcretion of uric acid in the kidneys, or a combination of both. The first attack of gout is often acute and extremely painful. Gout is common and occurs more frequently in men. Pseudogout (chondrocalcinosis) involves deposits of calcium pyrophosphate dihydrate (CPPD) crystals in joints, usually the knee.

Psoriatic arthritis

Autoimmune disorder affecting some people who have psoriasis, a disease that causes inflamed, scaly skin patches and discolored nails. People with psoriatic arthritis may develop painful, swollen joints with reduced motion, often in the fingers and toes. The arthritis may develop well after the initial psoriasis.

Infectious arthritis (septic arthritis)

Occurs when bacteria or viruses directly invade a joint and cause inflammation. The gonorrhea and staphylococcus bacteria are among the most common causes of this type of arthritis.

Lyme disease, an infection caused by tick bites, may lead to infectious arthritis if not treated promptly. Arthritis caused by Lyme disease is treated with antibiotics to address the underlying infection. Infectious arthritis may also develop after a traumatic injury that exposes a joint, or after joint surgery. It can destroy joints and is more common in people with RA, previous infections or previous joint surgery (e.g., arthroplasty).

Reactive arthritis

Occurs when an infection elsewhere in the body causes inflammation in a joint. Infections in the gastrointestinal and urogenital systems may trigger reactive arthritis. The sexually transmitted disease chlamydia may create reactive arthritis in joints. Certain gastrointestinal infections, such as salmonella, may also trigger reactive arthritis. One type of reactive arthritis is Reiter’s syndrome, which includes inflammation of the joints, eyes (conjunctivitis) and urethra (urethritis).

Ankylosing spondylitis

An uncommon condition that primarily affects the spine. As it progresses, it can also cause inflammation in other parts of the body, such as the joints between the ribs and spine and the joints of the hips, shoulders, knees and feet.

Many other conditions can cause arthritis-like pain, including lupus, TMJ disorder and chronic fatigue syndrome.

Risk factors and causes of arthritis

For most forms of arthritis, the exact cause is unknown. Infectious forms may be traced to a specific bacterial agent (such as gonorrhea) that invades a joint. Osteoarthritis (OA) is the result of the breakdown of cartilage, usually related to aging, but it is not fully understood why the degeneration begins. It may be the result of a malfunction in the cartilage and the metabolism of the underlying bone. Rheumatoid arthritis (RA), juvenile rheumatoid arthritis and psoriatic arthritis are autoimmune conditions, meaning the body's overactive immune system mistakenly attacks healthy tissues. The causes of autoimmune conditions are not well understood. Gout and pseudogout involve deposits of crystals in joints, a process that is only partly understood.

Elements called risk factors may increase the likelihood of developing a disease or condition. However, not everyone with the disease may exhibit risk factors, and not everyone with risk factors develops the disease. Some of the risk factors associated with forms of arthritis include:

  • Age. OA, by far the most common form of arthritis, is more likely to develop as people get older. About 70 percent of people over age 70 show evidence of OA in x-ray images, according to the American College of Rheumatology. Advanced age is also a risk factor for pseudogout. However, RA, ankylosing spondylitis, Reiter's syndrome and often gout are more common in earlier adulthood, and children can also get arthritis.
  • Weight. Excess weight may increase the likelihood of developing osteoarthritis. The extra stress placed on joints may contribute to the degeneration of cartilage.
  • Sex. Women are more likely than men to develop many types of arthritis, including OA and especially RA. Several arthritic conditions are more common in men, including gout, Reiter's syndrome and ankylosing spondylitis.
  • Personal medical history, including joint injury. People who have experienced acute joint trauma or overused certain joints in sports or in their work may develop arthritis. An earlier joint injury also makes it more susceptible to developing arthritis.
  • Genetics. Studies show that a genetic marker called HLA-B27 can be found in some people with certain forms of arthritis, such as ankylosing spondylitis. Many people with RA have a gene called HLA-DR4, and other gene variants including STAT4 and TRAF1-C5 have also been linked to RA. Not every person with arthritis has these genes. People who do have the gene have a greater tendency to develop some forms of the disease. Genetic variants have also been linked to OA, and heredity may play a role in developing other forms of arthritis as well.
  • Lifestyle. In addition to obesity, other lifestyle factors may contribute to certain forms of arthritis. For instance, gout may develop when excess uric acid accumulates in the joints. Uric acid comes from food or drink high in purines, so people with excess purines in their diet (e.g., alcohol, organ meats, anchovies) are more likely to develop gout.

Signs and symptoms of arthritis

The most common symptom for almost every form of arthritis is joint pain. People may experience stiffness when they first wake up in the morning that may last for up to an hour. Swelling (edema), redness or warmth in a joint may also signal arthritis. A person may have difficulty moving a joint or putting weight on it.

The joint pain may remain constant or recur in a joint, along with tenderness. In arthritic knees, the pain may feel as if there is no support within the leg. Some people may have a reduced range of motion, especially in their shoulders and arms.

Some signs of arthritis are apparent only with x-rays or other imaging studies. Arthritic joints will show worn cartilage, bone spurs where cartilage has degenerated and reduced space in the joint cavity.

Diagnosis methods for arthritis

Diagnosis of arthritis will involve a physical examination. A physician will examine the joints and muscles for tenderness and range of motion and note descriptions and incidences of pain and its duration. The diagnosis will also include a review of a medical history of any familial arthritic, rheumatic or autoimmune conditions, previous injuries or surgeries and general use of the joints. The patient may be asked to complete a pain assessment form.

Most diagnostic examinations where arthritis is suspected will include imaging studies. X-rays show the bones and joints and may indicate bony outgrowths or changes in the size of joint capsules or the position of bones. MRI (magnetic resonance imaging) and ultrasound images provide better views of the soft tissues. Ultrasounds may be useful for rheumatoid arthritis (RA) in the hands. Although x-rays are especially useful for osteoarthritis, they may be also used for suspected cases of RA to provide a baseline image.

Certain kinds of tests may be used to rule out conditions or specifically diagnose one form of arthritis. Many laboratory tests are used to screen for specific kinds of arthritis or other disease. Some of the blood tests include:

  • Complete blood count. Helps test for infectious arthritis, as white blood cells usually increase with this form of arthritis.
  • Antinuclear antibody (ANA) test. Helps test for certain autoimmune disorders such as RA and lupus.
  • Rheumatoid factor (RF) test. May indicate RA or other autoimmune conditions. The test may be negative in some RA cases when the disease is in remission, with no flare-ups of inflammation.
  • HLA-B27 test. Presence of this genetic marker in the white blood cells may indicate many conditions, including ankylosing spondylitis, RA, juvenile rheumatoid arthritis and Reiter’s syndrome.
  • Erythrocyte sedimentation rate (ESR). An elevated level of this blood test indicates inflammation, but can be caused by many forms of inflammation or infection.
  • C reactive protein test. An elevated level of this protein produced by the liver suggests an inflammatory disease such as RA.
  • Uric acid. A high level of uric acid in the blood may indicate gout. Uric acid may also be measured through a urine test.

Tests that analyze the synovial fluid from a joint may indicate gout, infectious arthritis or juvenile rheumatoid arthritis. Arthroscopy may be performed to examine a joint. A tissue sample of skin or muscle may be taken for a biopsy when forms of arthritis that involve the skin or muscle, such as psoriatic arthritis, are suspected.

Few laboratory tests aid in diagnosis of osteoarthritis, but they may be used later to monitor the effects of drugs used for treatment. The combination of findings from lab tests and a physical examination may provide a physician with enough information to diagnose a specific form of arthritis.

Treatment options for arthritis

Because arthritis generally cannot be cured, treatment usually concentrates on alleviating pain and slowing the degeneration of joints. Patients and their families can learn about arthritis, its progression and any limitations or complications the condition may present in their lives. Knowledge about the types of arthritis and likely course of the disease can help people preserve functioning joints and learn ways to manage with joints that are impaired.

Patients may want to keep a pain diary to monitor their symptoms, which can help them report the pain to their physician.

Many lifestyle factors can be adjusted for arthritis. Getting adequate amounts of sleep and resting when experiencing fatigue are important. Resting arthritic joints will also help. Home life can be altered with special fasteners and grips for weakened hands and items such as grab bars in showers and raised toilet seats can prevent falls.

Exercise and loss of excess weight may help certain forms of arthritis, especially osteoarthritis (OA). Maintaining a healthy weight relieves excess strain on the joints. Exercise that maintains muscle tone around joints helps support the joints. People with arthritis should consult their physician before beginning or changing any weight loss or exercise program. Exercise may also be part of a physical therapy program that addresses flexibility, strength, endurance, range of motion, balance and posture and ergonomics.

In addition, assistive devices can support arthritic joints and reduce the stress on them. These include braces, splints, canes, walkers and shoes with inserts. Occupational therapy can offer instruction in ways to conserve energy, modify tasks, protect joints and use adaptive equipment such as jar openers and shower benches.

Nutrition can also play a role. The Arthritis Foundation recommends a diet low in calories and saturated fats and rich in vegetables, fruits and whole grains. Gout patients often need to restrict meat and alcohol, which can trigger attacks.

Other methods of pain management for arthritis may include:

Heat, cold and water

A physician, physical therapist or occupational therapist can indicate which kind of therapy should be used for treatment. Heat (thermotherapy), such as hot packs, a paraffin hand bath or therapeutic ultrasound, relieves pain, muscle spasm and stiffness. Cold (cryotherapy), such an ice pack, provides a numbing effect and may reduce swelling. Water therapy (hydrotherapy) is often combined with thermotherapy or exercise therapy.

People with some medical conditions, such as poor circulation, should not use cold therapy, and conditions such as impaired sensation (e.g., from diabetic nerve damage) may rule out use of heat therapy.


A wide range of prescription and nonprescription medications are used for arthritis pain and inflammation, including:

  • Acetaminophen. May relieve pain associated with arthritis but does not affect inflammation. Misuse is a common cause of liver damage.
  • Nonsteroidal anti-inflammatory drugs (NSAIDs). Reduce pain and inflammation. They come in prescription and nonprescription forms. Some may affect renal or gastrointestinal function. Commonly used NSAIDs include aspirin, ibuprofen and naproxen. Among the prescription drugs are a group called COX-2 inhibitors. However, several of these were withdrawn from the market because of potentially serious side effects, such as increased risk of cardiovascular side effects.
  • Disease-modifying antirheumatic drugs (DMARDs). Suppress the overactive response of the immune system for patients with rheumatoid arthritis (RA), juvenile RA, ankylosing spondylitis and psoriatic arthritis. Side effects of DMARDs include liver and kidney complications and repression of immune responses to infection.
  • Biologic response modifiers (BRMs). Drugs that inhibit the production of the proteins called cytokines, which contribute to inflammation, and slow progression of the disease. Many RA patients respond favorably and achieve lengthy remissions when BRMs are combined with DMARD treatment.
  • Corticosteroids. May be given as pills or injections into the affected joint. These anti-inflammatories have some benefits for RA patients, but those may diminish over time. Long-term use of corticosteroids is associated with many side effects, such as osteoporosis, fractures, diabetes and glaucoma. Other medications are usually explored first. Repeated corticosteroid injection therapy is not recommended for people with OA.
  • Opioids. Narcotic analgesics used to treat severe pain.
  • Antidepressants. Primarily used to treat depression but sometimes prescribed for chronic pain due to arthritis or other conditions.
  • Creams. Some topical treatments may also alleviate arthritic pain. Capsaicin cream has the same active substance as hot chili pepper and may lessen the pain for OA patients. However, capsaicin may cause burning and redness in some individuals.


This can ease pain and stiffness, but the therapist should be familiar with arthritis, the Arthritis Foundation says.

Transcutaneous electrical nerve stimulation (TENS)

This form of electrical therapy, involving a device with wires and pads, delivers mild electric current to the skin and stimulates nerves to interfere with transmission of pain signals. It can alleviate pain or modify the perception of pain for OA patients.

Cognitive behavioral therapy

Patients can learn to replace negative thought patterns with positive ones.

Acupuncture and acupressure

Acupuncture is a traditional Chinese procedure in which needles are inserted at specific body points to control pain. Acupressure is a similar method that uses pressure at specific points instead of needles. Studies differ on the value of acupuncture and acupressure for arthritis pain. Some patients with soft tissue pain experience relief. Others show no change.


Patients can be trained to use the mind to help control the body. Limited research suggests biofeedback may ease arthritis, possibly by increasing circulation to joints and reducing inflammation and swelling, the Association for Applied Psychophysiology and Biofeedback says.


Many people with arthritis take supplements of glucosamine and chondroitin, but research has yielded mixed results. A study sponsored by the National Institutes of Health found that these supplements may help relieve moderate to severe pain from OA of the knee but may be no more effective than a placebo (sugar pill) for mild pain.

The American College of Rheumatology says supplements of fish oil containing omega-3 fatty acids might produce modest relief of arthritic pain, but it does not recommend S-adenosylmethionine (SAMe), an expensive supplement popular in Europe, and cautions that herbal remedies such as willow bark extract, ginger and Chinese thunder god vine may ease pain but can have dangerous side effects.

Supplements and herbs are not regulated by the U.S. Food and Drug Administration. Patients are advised to discuss any treatments or supplements with their physician, including any complementary or alternative medicine therapies.


Several types of surgery can correct arthritic damage. Some of the most common include:

  • Arthroscopy. A flexible lighted tube is inserted through an incision into a joint to remove debris from the joint cavity or inflamed tissue.
  • Arthroplasty. Open surgery on damaged joints may also be performed to remove inflamed tissue or fuse parts of the joint. When a joint is severely damaged, surgeons can replace it. Joint replacement is most commonly performed for the knees and hips but can also be performed on some other joints, including the shoulder.
  • Corrective surgery. May be used on tendons and deformed joints, especially for people with RA.
  • Spinal surgery. Several types of spinal operations may be performed for patients with severe RA or ankylosing spondylitis, to realign the spine, ease pressure on compressed nerves or fuse the vertebrae.

Prevention methods for arthritis

People may avert some arthritic conditions by avoiding infections — for example, using tick repellent to prevent Lyme disease and practicing safe sex to prevent the sexually transmitted diseases that can cause Reiter's syndrome.

However, there is no sure way to prevent most forms of arthritis. Yet many of the lifestyle changes used to treat arthritis may help prevent it or delay its onset. Avoiding trauma and injury, through means such as using seatbelts and wearing protective sports equipment, may help keep from predisposing the joint to early osteoarthritis (OA). Avoiding obesity or losing weight if necessary reduces stress and weight on the body's joints. Healthy levels of exercise (approved by a physician) can help maintain muscle strength and minimize the likelihood of joint injury.

Another preventive measure is to quit smoking or never start. In addition to the many other health hazards caused by tobacco use, researchers have found that some smokers have an increase risk of rheumatoid arthritis and might be at risk for a worsening of OA.

A healthful diet rich in produce may also help. Recent studies suggest that carotenoids (found in orange and yellow vegetables and fruits) and certain enzymes in cruciferous vegetables (the broccoli and cabbage family) could protect the joints and help stave off arthritis. Some research indicates the mineral selenium, found in many foods, may help prevent OA.

Good posture and ergonomics can prevent exacerbations of arthritis and help people function in the workplace and in other daily tasks.

Questions for your doctor regarding arthritis

Patients may wish to ask their doctor the following questions about arthritis:

  • What type of arthritis do I have or am I suspected of having?
  • What tests might I need to undergo, and what do they involve?
  • What do my test results indicate?
  • What is the expected course of my condition? Is it likely to worsen over time? Will it involve alternating periods of flare-up and remission?
  • What over-the-counter medications should I use? Are there any I should avoid?
  • What prescription medications will help my arthritis pain? Do they have side effects or risks?
  • What kind of exercise do you recommend for me? Are there any exercises I should avoid?
  • How can I tell when I should be active and when I need to rest?
  • When can heat therapy or cold therapy help me, and are there times I need to avoid them?
  • Do you recommend physical therapy, occupational therapy, acupuncture, stress management or other therapies for me?
  • Might I need surgery for my arthritis? If so, what are my options, and what do they involve?
  • Does having arthritis put me at risk for other conditions?
  • Is there anything I can do to prevent arthritis or its complications?