Medically reviewed by Carina Fung, PharmD, BCPPS

What is arthritis?

Arthritis1 is inflammation (swelling) of the body's joints. The condition most commonly causes pain and feelings of stiffness or tenderness in the joints.

Joints are the places in the body at which bones come together, such as the knees, wrists, fingers, toes, and hips. Arthritis can affect just one joint or multiple joints at the same time.

Source: Getty Images

Arthritis is a progressive condition, meaning it gets worse with age. In some cases, it can become severe and quite painful over time.

Whether an individual will develop arthritis depends on a multitude of risk factors, including regular wear and tear over time. How arthritis is treated depends upon the type of arthritis a patient has. There are many different combinations of medication and physical treatment that can help alleviate the symptoms of arthritis, with the general goal of treatment being decreased discomfort and improved quality of life.

Types of arthritis

There are many different types2 of arthritis (over 100, in fact), the two most common being osteoarthritis and rheumatoid arthritis.

Some common forms of arthritis include:

  • Ankylosing spondylitis: A type of arthritis that affects the spine. Its main symptoms are pain and stiffness. It can also cause the bones of the spine’s joints to become fused together, decreasing flexibility and sometimes resulting in a hunched posture.
  • Gout: A painful inflammatory arthritis caused by the buildup of uric acid inside of the joints. It most commonly occurs in the big toe, but can also be found in the knee, elbow, wrist, foot, and finger.
  • Fibromyalgia: A chronic musculoskeletal pain syndrome that amplifies painful sensations by affecting the brain’s processing of pain signals. This causes tenderness, pain, and severe fatigue accompanied by problems with sleep, mood, and memory.
  • Osteoarthritis: Osteoarthritis—the most common type of arthritis—is what most people are referring to when they talk about “arthritis” in general. It occurs when the cartilage that protects and cushions the joints wears down over time.** **
  • Polymyalgia rheumatica: An inflammatory disease found most commonly in older adults and women that causes stiffness and flu-like symptoms.
  • Pseudogout: Occurs when calcium pyrophosphate crystals accumulate in the joints. Pseduogout can be found anywhere in the body, but most commonly affects the knees.
  • Psoriatic arthritis: An inflammatory arthritis that occurs over time in roughly 10–20% of people with psoriasis3. While different from rheumatoid arthritis, the two conditions share many of the same symptoms.
  • Reactive arthritis: Joint pain or swelling that results from an infection in another part of the body. It is most often triggered by infection in the intestines, genitals, or urinary tract and usually targets the knees, ankles, and feet.
  • Rheumatoid arthritis: The second most common form of arthritis, rheumatoid arthritis is an autoimmune disorder that causes the body to attack the synovial fluid in the joints, which leads to stiffness, pain, and deformities in the joints.

How common is arthritis?

Arthritis is relatively common: there are an estimated 54 million4 American adults (23%) with some type of arthritis or joint-related pain. Of those with arthritis, about 24 million are limited in their activities as a result of the condition.

Arthritis can affect people of all ages (roughly 300,0005 children have some form of arthritis), but it is most common in older adults. 60% of people with arthritis are between the ages of 18–64, while osteoarthritis, the most common form of arthritis, is found in roughly 20 million adults.

What causes arthritis?

There are many different causes6 of arthritis. Some can be prevented or slowed in their progression, while others (such as genetics) are out of one’s control.

Osteoarthritis, the most common form of arthritis, occurs as a result of damage to the cartilage that cushions and protects the joints. This damage can occur over time due to normal wear and tear or more quickly after a joint infection or injury.

Cartilage, found at the end of the joints, helps reduce friction to ease joint movement. When this cartilage wears down, the bones are no longer protected and begin to rub against one another. This leads to pain, swelling, and limited mobility, as well as inflammation of the joint lining.

Rheumatoid arthritis, the second most common type of arthritis, is caused by a malfunction in the immune system that causes it to attack the lining (synovial membrane) of the joint capsule (a tough membrane that envelops the different parts of a synovial joint). This causes the synovial membrane to become swollen and inflamed. Over time, rheumatoid arthritis can destroy the cartilage and bone within a joint.

Risk factors for arthritis

Certain pre-existing conditions, as well as environmental and genetic factors7, can increase your risk of developing arthritis, including:

  • Overweight: Being overweight or obese adds increased strain on the joints (particularly those in the knees and hips), causing them to break down over time.
  • Abnormal metabolism: Metabolic issues can lead to gout and pseudogout, both of which are out of one’s control.
  • Infections: Bacterial and viral infections can cause reactive arthritis to form. Certain other infections, such as Lyme disease, can also jumpstart arthritis.
  • Joint Injury: Overuse or injury can add repetitive stress to a given area, and cause osteoarthritis to form in that joint.
  • Smoking: Smoking cigarettes increases the risk of arthritis, as it makes it harder to stay physically active and maintain healthy joints.
  • Joint injury: Experiencing a joint injury increases your risk of developing arthritis in that joint.
  • Age: Older adults are at increased risk of developing arthritis.
  • Biological sex: Arthritis is more common in women than in men.
  • Genetics: Having a family history of arthritis can increase your likelihood of developing the disease. Additionally, people who have or have a family history of HLA (human leukocyte antigen)8 have a higher risk of arthritis and more severe symptoms.

Arthritis symptoms

The most common signs and symptoms9 of all forms of arthritis include:

  • Joint pain: May be felt when folding or moving an affected body part. Joint pain may worsen over time.
  • Stiffness: Tension or difficulty when moving, especially when waking up or standing from a seated position.
  • Tenderness: The affected area is sore to the touch, similar to a bruise.
  • Limited movement: Loss of full range of motion.
  • Grating: Sensation caused by friction when bones and joints rub against one another.
  • Bone spurs: Occur when lumps of bone form around a joint. These can cause pain and mobility issues.

Rheumatoid arthritis symptoms

The symptoms of rheumatoid arthritis10 (which often overlap with those of osteoarthritis) may include:

  • Fatigue: Feeling tired and never well-rested, lacking energy, and being lethargic (especially when getting up in the morning)
  • Morning stiffness: Being especially stiff or immobile after waking up
  • Joint stiffness: Usually occurs in multiple smaller joints (such as those in the hands) at the same time.
  • Joint tenderness
  • Minor swelling: Inflammation can cause the joints to swell, resulting in a warm feeling and a visibly raised or swollen lump in the affected area.
  • Fever: While this can be a sign of infection, the symptoms of RA may sometimes be accompanied by fever.
  • Numbness: Inflammation can cause added pressure on the nerves, sometimes leading to numbness in the affected area.
  • Dry/inflamed eyes
  • Difficulty sleeping: Can be due to pain from moving and overall discomfort

Psoriatic arthritis symptoms

This condition can affect multiple areas of the body that may not appear to be directly connected to the joints. Because of this, the symptoms of psoriatic arthritis11 can differ slightly from those of other forms of arthritis. They may include:

  • Swollen fingers/toes: Psoriatic arthritis can cause severe, painful swelling in the fingers and toes (and sometimes in the hands and feet). Swollen areas will be red and warm to the touch. While swollen knuckles can indicate rheumatoid arthritis, swelling along the entire length of the finger may be a sign of psoriatic arthritis.
  • Foot pain: This occurs most often at the points where the tendons and ligaments attach to the bones, especially at the back of the heel. Pain may also be felt in the sole of the foot (called plantar fasciitis). Pain felt directly in the foot is usually a sign of osteoarthritis or rheumatoid arthritis, while pain or swelling in the toes is more likely a sign of gout or psoriatic arthritis.

There are shoe brands made specifically for people with arthritis-related foot issues. If your arthritis is severe, you may benefit from thick soles, such as rocker soles.

  • Lower back pain In some cases, psoriatic arthritis leads to a condition called spondylitis12. This can cause inflammation of the joints between the vertebrae of the spine and those between the spine and pelvis. Arthritis in this part of the body can cause stiffness and lower back pain that can run as far down as the buttocks.
  • Nail separation: Changes to the nails—such as denting or bumpiness—may be a sign of psoriatic arthritis. These changes result from inflammation in the nailbed. Separation can occur in small areas or across the entire nail. When a small area of the nail comes up from the bed, it may look like a white spot.
  • Eye inflammation: Psoriatic and rheumatoid arthritis can both cause eye problems, including inflammation, irritation, pain, and redness. This occurs when the white part of the eye (sclera) becomes inflamed. Many patients use eye lubricants, such as drops or gels, to soothe uncomfortable symptoms.
  • Elbow pain: While the most common type of arthritis seen in the elbow is rheumatoid arthritis, psoriatic arthritis may also cause tenderness and soreness in the joint. This discomfort can occur when bending and straightening the elbow.
  • Fatigue: As with other forms of arthritis, it is common for patients with psoriatic arthritis to feel fatigued much of the time. This can be a result of chronic pain as well as high levels of cytokines—a chemical that is produced as a result of inflammation—in the body.

Complications from arthritis

Aside from impacting general quality of life, arthritis can lead to a number of related health conditions. Some complications13 associated with arthritis include:

  • Carpal tunnel syndrome: This is caused by compression of the nerves that control the hands’ movements. It can cause aching, numbness, and tingling in the hands. Of the entire population of people with rheumatoid arthritis, 10% also have carpal tunnel syndrome.
  • Inflammation: Inflammation is caused by an overactive immune system. It usually affects many joints throughout the body at the same time. In some cases, inflammation can become widespread and move throughout the body to the lungs, heart, or eyes.
  • Joint damage: Without timely treatment, arthritis can do permanent damage to the joints and permanently restrict movement and sensation. This occurs most commonly in rheumatoid arthritis when painful swelling results in bone erosion and joint deformity.
  • Cardiovascular disease: Arthritis raises your overall risk of developing cardiovascular disease. While the exact link between arthritis and cardiovascular disease is not clear, it is known that this risk can be lessened by eating a healthy diet and not smoking.
  • Cervical myelopathy: This condition is caused by the compression of the spinal cord in the neck. Its progression is generally a slow and very painful process. While fairly uncommon in the total population of those who have arthritis, cervical myelopathy is a very serious condition.
  • Reduced mobility: Arthritis can make it more difficult to move around. This is generally due to joint pain, swelling, and the damage that can occur in weight-bearing joints, such as those in the hips, ankles and knees. Reduced mobility can affect work, as well as the ability to complete normal daily tasks.
  • Stress fractures: The bones of people with arthritis often degrade over time. This causes them to become brittle and more susceptible to fractures.

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