Arthritis describes a group of conditions in which inflammation or disease affects one or more joints. Arthritis can affect any joint in the body but is most common in weight-bearing joints such as the spine, knee, and hip. Arthritis may involve one joint (monoarthritis) or more than one joint (oligoarthritis or polyarthritis).
Arthritis is a leading cause of disability worldwide. This group of conditions can be related to several underlying causes, such as:
- Gradual wear and tear on the joints
- An autoimmune disorder in which the immune system attacks otherwise healthy cells
- An injury, such as a fracture or broken bone
- Infection, often with a virus or bacteria
- The buildup of crystals in and around the joint, including those formed of uric acid and calcium
In patients with arthritis, a joint becomes inflamed, which leads to swelling, stiffness, and pain. If left untreated, inflammation can cause long-term or permanent disability. There are over 100 different types of arthritis. The most common types of arthritis include:
Osteoarthritis: Osteoarthritis is the most diagnosed form of arthritis. Frequently affecting the hips, knees, and hands, osteoarthritis develops when the cartilage within a joint starts to break down.
Rheumatoid arthritis: Rheumatoid arthritis is an autoimmune disorder in which the immune system attacks healthy cells, causing inflammation, pain, and swelling in the affected joints.
Gout: Gout is associated with excess uric acid in the body that forms needle-like crystals in affected joints, and other tissues. Episodes, called flares, can start suddenly and may last for days or weeks.
Ankylosing spondylitis: A chronic form of arthritis, that mainly affects the spine, causing painful inflammation of the joints between the vertebrae and between the spine and pelvis. As the disease progresses, it can sometimes cause the bones in the spine to fuse together.
Psoriatic Arthritis: This type of arthritis occurs in some people who have a skin condition called psoriasis. Psoriatic arthritis is marked by painful, swollen, and stiff joints as well as other symptoms.
Other types of arthritis include juvenile rheumatoid arthritis, a diverse condition that first appears in children younger than 16 years of age, septic arthritis, and reactive arthritis. Septic arthritis is caused by an infection in a joint, while reactive arthritis develops in response to an infection in another part of the body.