Recent research has pointed to an underlying inflammatory process that makes certain people susceptible to osteoarthritis.

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Arthritis refers to joint inflammation, but the term also is more loosely used to describe any disorder that affects the joints. It is a symptom, rather than a specific disease. Arthritic conditions fall into a wider disease category known as “rheumatic diseases.” There are more than 100 types, each with their own pathology.

Inflammation can affect tendons, ligaments, bones, and muscles. Inflammation in a joint produces a variety of symptoms, including redness, heat, swelling, pain, stiffness, and loss of function.

Broadly speaking, there are four types of disease process that can cause arthritis: degenerative, inflammatory, metabolic, and infectious.

Degenerative Arthritis

Degenerative arthritis is caused largely by the wear-and-tear of everyday life. The protective mechanisms within the joint deteriorate, allowing bone to rub on bone or soft tissue, resulting in pain, swelling, and stiffness. Over time, this may lead to joint instability, deformity, weakness, chronic pain, disability, and reduced quality of life. The most common type of degenerative arthritis is osteoarthritis (OA), which may occur due to the aging process or trauma to the joint. Recent research has pointed to an underlying inflammatory process that makes certain people susceptible to OA.

Inflammatory Arthritis

A healthy immune system protects the body from foreign invaders, such as bacteria and viruses, and from injury. In inflammatory arthritis, the immune system begins to attack the body’s own tissue. The resulting inflammation may strike the joints and other organs, like the eyes and skin. Rheumatoid arthritis and psoriatic arthritis are the two most common types of inflammatory arthritis. The inflammatory response is thought to be triggered by a combination of genetic susceptibility and environmental factors, such as smoking.

Metabolic Arthritis

Metabolic arthritis occurs due to a disorder of the metabolism of chemicals within the body. Gout is the most common form, and occurs due to a problem with purine metabolism. Purines are biochemical compounds found in food and made by the body. When purines are broken down, they form uric acid, which is normally excreted by the kidneys. Sometimes too much uric acid is eaten or produced, or the kidneys do not keep up with excretion. This results in hyperuricemia (a buildup of uric acid in the blood). In susceptible individuals, uric acid crystals then form in the joint, causing inflammation. Gout is characterized by acute flare-ups that occasionally become chronic and may cause significant damage to a joint.

Infectious Arthritis

Rarely, an infectious agent such as a bacterium, virus or fungus, reaches the joint and causes inflammation. Pathogens include Salmonella enterica and Shigella (gut bacteria), Chlamydia trachomatis and Neisseria gonorrhoeae (sexually transmitted diseases), and hepatitis C. Prompt treatment with antibiotics can cure infectious arthritis, but at times it may become chronic.

There are more than 100 types of arthritis, so when it comes to diagnosis the first challenge is to determine the cause of the inflammation. The second challenge is to evaluate the extent of tissue involvement and level of disease. For example, is there an acute and self-limiting inflammation of the joint capsule that responds quickly to simple painkillers? Or is there progressive cartilage erosion, bone damage, and significant disability warranting surgical intervention?

When to See Your Doctor

If you are otherwise well and have mild, short-lived joint pain that responds well to simple interventions such as painkillers and icepacks, you may not need to see your doctor. If, however, you have low-level pain over several weeks or the sudden onset of significant acute pain, joint injury, or neurological symptoms like numbness, it’s time to consult a physician.

For more information about arthritis, check out “Arthritis Guide to Diagnosis and Treatment” at www.UniversityHealthNews.com.