Arthritis affects the musculoskeletal system, specifically the joints. It is the main cause of disability among people over fifty-five years of age in industrialized countries.

The word arthritis comes from the Greek arthron meaning "joint" and the Latin itis meaning "inflammation". The plural of arthritis is arthritides.

This Medical News Today articles includes details on the definition of arthritis, its causes, the four main types of the disease, its signs and symptoms, how arthritis affects people, the benefits of physical and occupational therapy, currently available medications, and the impact of diet and exercise.

Here are some key points about arthritis. More detail and supporting information is in the main article.

• Arthritis affects the musculoskeletal system, specifically the joints.
• About 1 in every 5 American adults, i.e. 50 million people, have doctor-diagnosed arthritis.
• Arthritis is not a single disease - it is a term that covers over 100 medical conditions. Osteoarthritis (OA) is the most common form of arthritis.
• Most types of arthritis are caused by a combination of several factors working together including genetic makeup, a physically demanding job, previous injury, infection or allergies, certain foods, obesity, autoimmune disease.
• The most common forms of arthritis are osteoarthritis, rheumatoid arthritis, infectious arthritis and juvenile rheumatoid arthritis.
• Physical therapy and occupational therapy can help maintain joint mobility and range of motion.
• Physical therapy, apart from significantly improving function and reducing pain, has been shown to delay the need for surgical intervention in advanced cases ⁸.
• Occupational therapy can teach you how to reduce the strain on your joints as you go about your daily activities.
• Doctors warn that inactivity could harm the health of most patients with arthritis or some kind of rheumatic disease. Inactivity raises the risk of cardiovascular disease and diabetes type 2.
• NSAIDs (nonsteroidal anti-inflammatory drugs) are the most commonly prescribed drugs for arthritis patients.

Types of arthritis

There are over 100 types of arthritis. Here is a description of some common ones, together with the causes:

Osteoarthritis

With osteoarthritis, the cartilage loses its elasticity. If the cartilage is stiff it becomes damaged more easily. The cartilage, which acts as a shock absorber, will gradually wear away in some areas. As the cartilage becomes damaged tendons and ligaments become stretched, causing pain. Eventually the bones may rub against each other causing very severe pain.

Rheumatoid arthritis

This is an inflammatory form of arthritis. The synovial membrane (synovium) is attacked, resulting in swelling and pain. If left untreated the arthritis can lead to deformity.

Rheumatoid arthritis is significantly more common in women than men and generally strikes when the patient is aged between 40 and 60. However, children and much older people may also be affected.

During the first ten years after diagnosis, patients with rheumatoid arthritis have a higher risk of blood clots.

Infectious arthritis (septic arthritic)

Infectious arthritis is an infection in the synovial fluid and tissues of a joint. It is usually caused by bacteria, but could also be caused by fungi or viruses.

Bacteria, fungi or viruses may spread through the bloodstream from infected tissue nearby, and infect a joint.

Most susceptible people are those who already have some form of arthritis and develop an infection that travels in the bloodstream.

Juvenile rheumatoid arthritis (JRA)

Juvenile rheumatoid arthritis is a type of arthritis that affects a person aged 16 or less. JRA can be various forms of arthritis; it basically means that a child has it.

There are three main types:

1. Pauciarticular JRA, the most common and mildest. The child experiences pain in up to 4 joints.
2. Polyarticular JRA affects more joints and is more severe. As time goes by it tends to get worse.
3. Systemic JRA is the least common. Pain is experienced in many joints. It can spread to organs. This can be the most serious JRA.