Understanding Arthritis -- the Basics

Medically Reviewed by David Zelman, MD on December 06, 2022
5 min read

Arthritis means inflammation of a joint, where two bones meet. The main symptoms are pain, stiffness, and swelling in the joints and surrounding tissues.

But just because you have these symptoms doesn’t mean you have arthritis. Muscle strain, bursitis, tendinitis, and other conditions can have the same symptoms.

In addition, different types of arthritis have different causes and a number of additional symptoms, and so may require a variety of treatments.

That’s why it’s important for your doctor to confirm first, whether you have arthritis, and second, what type it is.

While there are over 100 types of arthritis, there are two that are the most common: osteoarthritis and rheumatoid arthritis.

Osteoarthritis is the most common type, affecting more than 32 million U.S. adults, mostly older individuals. It is the mechanical, or “wear and tear,” form of the disease in which the protective cartilage that cushions the ends of your bones slowly wears away.

Rheumatoid arthritis is the second most common type, affecting 1.3 million people in the United States. Here, the body's immune system misfires and starts to attack your joints (autoimmune disease). It can begin at any point in life, but generally starts between ages 30 and 50, and affects women two to three times more often than men.

Other, less common types of arthritis include gout, infectious (septic) arthritis, juvenile arthritis, ankylosing spondylitis, psoriatic arthritis, and others.


Osteoarthritis: In some cases, the cause is nothing more than the normal wear and tear of daily life. In others, repeated motion like swinging a hammer or a tennis racket many times over seems to be the culprit. But it’s not clear why these are likely to cause arthritis in some people more than others. Doctors suspect your genes play a part, especially in people who develop the disease at an early age.

Other causes of osteoarthritis include:

  • Being overweight (puts more strain on weight-bearing joints, especially knees)
  • Injury or trauma to joint surfaces

Rheumatoid arthritis (RA): Doctors know your immune system mistakenly starts to attack your joints (autoimmune disease), but they don’t know why it happens. Some things seem to raise your risk of RA. These include:

Osteoarthritis: The main symptom of osteoarthritis is pain in your joints that worsens over time. It can happen to any joint, but is most common in the hands, knees, hips, and spine.

It’s typically most uncomfortable and stiff in the morning when you wake up. You might not be able to move your joints as freely as you could in the past and you may notice a scraping or crunching feeling when you do (crepitus).

Symptoms tend to build up slowly over years as cartilage wears away and bone starts to rub on bone. Over time, this can change the shape and appearance of a joint. In serious cases, bony growths called spurs may cause painful nerve damage, especially around the spine. This can change your posture and make it harder to get around.

Rheumatoid arthritis: Pain and swelling in the joints of the hands, especially the knuckles and next closest finger joints, are common. You might also notice this in the wrists, elbows, shoulders, knees, and feet.

Symptoms tend to come on more quickly than with OA (in a few weeks or months) and they might worsen for a time (flare) and get better for a time (remission). Specific signs and symptoms of RA might include:

  • More than one tender and swollen joint
  • More than one stiff joint
  • More than one painful joint
  • Same symptom on both sides (as in both hands or both knees)
  • Unexplained tiredness
  • General weakness
  • Unexplained weight loss

Without treatment, RA can cause hands and feet to become misshapen as muscles weaken, tendons move out of position, and the ends of bones are damaged. More rarely, RA can cause damage to other parts of the body, including the lungs, eyes, nerves, and skin. Early treatment of rheumatoid arthritis can relieve symptoms and prevent serious disability in most people.

Your doctor will take a full health history of you and ask about health problems of family members. They’ll examine you, ask you about your symptoms and may ask about your diet and exercise habits. They might also do imaging of your joints and test your blood and urine. If your doctor suspects RA, they will likely send you to a rheumatologist.

This will depend to a great extent on exactly what type of arthritis you have. Your doctor can help you treat and manage your symptoms, but the nature of that treatment depends on which symptoms or complications you have.

Changes in diet, lifestyle, and exercise habits may play a part. After that, it’s important to build a plan to manage your condition that you and your doctor agree on. This might involve a number of prescription or over-the-counter medicines along with heat, ice, physical therapy, injections, and joint supporting devices like braces.

Your health care provider might also suggest surgery in serious cases or as a last resort.

Ankylosing spondylitis is a type of arthritis that inflames the joints around your spine, hips, and pelvis. There’s no cure, but your doctor can help you manage your symptoms, which can be somewhat different in each person.

Like RA, symptoms tend to flare up and then get better for a while before they return. Serious pain and stiffness in the lower back and hips are quite common. Other symptoms could include:

  • Back pain and stiffness, especially in early morning
  • Joint pain and stiffness in hips or even feet, knees, and shoulders
  • Gut pain and diarrhea
  • Posture that stoops forward to relieve pain
  • Difficulty taking a deep breath of air

AS symptoms can mimic other health conditions, so it’s important to see your doctor for a correct diagnosis.

Gout happens when a waste product called uric acid builds up in the blood and crystallizes in and around the joints, typically the great toe but also the ankle, foot joints, elbows, wrists, and knees. Most commonly it suddenly causes a painful and swollen joint. Your doctor can help you treat an attack with rest and medication. Some drugs, as well as better diet and exercise habits, can reduce future attacks and other problems linked to gout by lowering the level of uric acid in the blood.

Juvenile rheumatoid arthritis comes in many forms. Still's disease affects the whole body. It often causes daily fevers and low blood counts (anemia). It sometimes also affects the heart, lungs, eyes, and nervous system.

Other kinds of juvenile RA are closer to the adult form and treatment is mostly the same. As with adults, long-lasting disability is far less common with early treatment of the disease.

Infectious arthritis is caused by a bacterial or viral infection. It usually travels to a joint from other parts of the body, but may also enter directly when an injury introduces bacteria to a joint. Examples of infection include staph infection, tuberculosis, gonorrhea, or Lyme disease.