Arthritis is inflammation of one or more of the body's joints that causes pain and stiffness. Although arthritis is mainly an adult disease, some forms affect children.
There are many types of arthritis. They include osteoarthritis, inflammatory arthritis, post-traumatic arthritis, and septic (infectious) arthritis.
Arthritis may be caused by wear and tear on the articular cartilage through the natural aging process (osteoarthritis), or it may develop following an injury (post-traumatic arthritis). Inflammatory arthritis, such as rheumatoid arthritis or lupus arthritis, is the result of a systemic disease throughout the body.
Regardless of whether arthritis is caused by injury, normal wear and tear, or systemic disease, the affected joint becomes inflamed, causing swelling, pain, and stiffness. Inflammation is one of the body's normal reactions to injury or disease. In arthritic joints, however, inflammation may cause long-lasting or permanent disability when it destroys the joint's cartilge. There are 4 major categories of arthritis:
The most common type of arthritis is osteoarthritis. Also known as "wear and tear" arthritis, osteoarthritis occurs when the cartilage that cushions and protects the ends of bones gradually wears away.
Osteoarthritis results from overuse, trauma, or the natural degeneration of cartilage that occurs with aging. There is a strong genetic component to osteoarthritis, but the genetics are complex and poorly understood. There is no single known osteoarthritis gene; the condition is likely due to a combination of many genes. Scientists call this type of genetics "multifactorial."
Osteoarthritis is often more painful in joints that bear weight, such as the knee, hip, and spine. However, joints that are used extensively in work or sports, or joints that have been damaged by injury may also show signs of osteoarthritis.
In many cases, bone growths called spurs develop at the edges of osteoarthritic joints. The bone can become harder (sclerosis). The joint becomes inflamed, causing pain and swelling. Continued use of the joint is painful.
As the name implies, inflammatory arthritis results from an excessive inflammatory response inside a joint. It often is the result of an overactive immune system (autoimmune arthritis) but can also be caused by certain diseases (such as Lyme disease) or by the buildup of crystals in the joint (such as gout or psudogout). The most common cause of inflammatory arthritis is rheumatoid arthritis.
Rheumatoid arthritis is a chronic autoimmune disease that afects many parts of the body, but mainly the joints. The body's immune system, which normally protects the body, begins to produce substances that attack the body. In rheumatoid arthritis, the joint lining swells, invading surrounding tissues. Chemical substances are produced that attack and destroy the joint surface.
Rheumatoid arthritis may affect both large and small joints in the body and also the spine. Swelling, pain, and stiffness usually develop, even when the joint is not used. In some circumstances, juvenile arthritis may cause similar symptoms in children.
Psoriatic arthritis is associated with the skin disease psoriasis. While it may involve larger joints such as the knees it often presents with symptoms in smaller areas such as the distal joints at the tips of the fingers and toes.
Crystalline Arthropathy (gout or pseudogout)
Gouty arthritis develops as the result of uric acid buildup in the bloodstream. The uric acid forms crystals that cause acute inflammation in a joint. The big toe, ankle, knee, and elbow are the most common joints affected. A gout attack can be acutely painful and may look like an infection (septic arthritis). The inflamed joint becomes red and very sensitive to touch. Gout attacks are most often treated with medication rather than surgery. Long term, many patients develop soft tissue masses (tophi) over the affected joints.
In pseudogout, calcium pyrophosphate crystals depost in the joint and cause similar inflammation as the uric acid crystals of gout. Left untreated, the inflammation caused by these crystals may lead to breakdown of the cartilage of the joint.
Lyme arthritis can be one of the side effects of Lyme disease, a systemic infection caused by a tick bite. Lyme arthritis can present acutely as pain and swelling in early stages of the disease. Lyme disease is treated with antibiotics. Left untreated, Lyme disease can lead to chronic arthritis.
Spondylytic arthritis mostly affects the spine. The most common form is ankylosing spondylitis. It often presents as low back pain with initial changes seen at the sacroiliac joints in the pelvis. A doctor can confirm this diagnosis with a positive blood test, HLA-B27.
Lupus is an autoimmune disease that affects the blood and multiple organs, including the kidneys, skin, and heart. Lupus arthritis can be systemic and cause chronic pain in multiple joints.
Juvenile arthritis is the most common type of arthritis in children. It is estimated that more than 250,000 children under the age of 16 in the United States are affected. There are several types of the disease and most are different from rheumatoid arthritis in adults.
The above is not an exhaustive list. There are many more less common causes of inflammatory arthritis.
Post-traumatic arthritis results from an injury to the joint due to trauma. If a broken bone or fracture extends into a joint it will damage the smooth cartilage that covers the joint's surface. The surface becomes uneven and causes friction as the joint moves. Over time, the joint breaks down and becomes arthritic.
Septic arthritis is an infection of the joint. Bacteria most often reach the joint through the bloodstream from an infection in another part of the body, such as the urinary tract. Infected joints are typically warm, red, and acutely tender. They are often swollen due to pus in the joint. An infected joint often needs surgical drainage in addition to antibiotic treatment.