Understanding arthritis – the basics
What is arthritis?
Arthritis is a general term for a group of more than 100 diseases. The word arthritis means joint inflammation. Inflammation is one of the body's natural reactions to disease or injury, and includes swelling, pain and stiffness. Inflammation that lasts for a very long time or recurs, as in arthritis, can lead to tissue damage.
A joint is where two or more bones come together, such as the hip or knee.
The bones of a joint are covered with a smooth, spongy material called cartilage, which cushions the bones and allows the joint to move without pain. The joint is enclosed in a fibrous casing called the synovium. The synovium's lining produces a slippery fluid, called synovial fluid, that nourishes the joint and helps limit friction within. Strong bands of tissue, called ligaments, connect the bones and help keep the joint stable. Muscles and tendons also support the joints and enable you to move.
With arthritis, an area in or around a joint becomes inflamed, causing pain, stiffness and, sometimes, difficulty moving. Some types of arthritis also affect other parts of the body, such as the skin and internal organs.
Types of arthritis
There are more than 100 different types of arthritis. Some of the more common types include:
Osteoarthritis: This is the most common type of arthritis. It occurs when the cartilage covering the end of the bones gradually wears away. Without the protection of the cartilage, the bones begin to rub against each other and the resulting friction leads to pain and swelling. Osteoarthritis can occur in any joint, but most often affects the hands and weight-bearing joints such as the knee, hip and facet joints (in the spine). Osteoarthritis often occurs as the cartilage breaks down, or degenerates, with age. For this reason, osteoarthritis is sometimes called degenerative joint disease.
Rheumatoid arthritis: Rheumatoid arthritis is a long-lasting disease that can affect joints in any part of the body but most commonly the hands, wrists and knees. With rheumatoid arthritis, the immune system -- the body's defence system against disease -- mistakenly attacks itself and causes the joint lining to swell. The inflammation then spreads to the surrounding tissues, and can eventually damage cartilage and bone. In more severe cases, rheumatoid arthritis can affect other areas of the body, such as the skin, eyes lungs and heart.
Gout: Gout is a painful condition that occurs when the body cannot eliminate a natural substance called uric acid. The excess uric acid forms needle-like crystals in the joints that cause swelling and severe pain. Gout most often affects the big toe, knee and wrist joints.
Juvenile idiopathic arthritis, also known as juvenile rheumatoid arthritis, is characterised by persistent arthritis in one or more joints for at least six weeks and after other possible illnesses have been ruled out. Treatment is essentially the same as for adult rheumatoid arthritis, with heavy emphasis on physical therapy and exercise to keep growing bodies active. Permanent damage from juvenile idiopathic arthritis is now rare, and most affected children recover from the disease fully without experiencing any lasting disabilities.
Septic (infectious) arthritis refers to various ailments that affect larger arm and leg joints as well as the fingers or toes. It is caused by a bacterial or viral infection of the joints and typically occurs around the time a person has other diseases, such as staph infection, tuberculosis, gonorrhoea or Lyme disease. It can also be a complication of injury.
Septic arthritis is much less common than arthritic conditions that come on with age. Because the symptoms may be masked by the primary injury or illness, septic arthritis may go unnoticed and, if left untreated, can result in permanent joint damage.
Psoriatic arthritis is a chronic disease characterised by inflammation of the skin (psoriasis) and joints (arthritis). With psoriasis, there are patchy, raised, red and white areas of skin inflammation with scaling. Psoriasis usually affects the tips of the elbows and knees, the scalp, the navel, and the skin around the genital areas or anus. Psoriatic arthritis can cause a sausage-like swelling of fingers and toes, which usually occurs with fingernails that are pitted or discoloured. In some people with psoriatic arthritis, only one joint is affected. For example, a person may be affected in only one knee. Sometimes the spine is affected, or just the fingers and toes. Psoriatic arthritis usually strikes around the age of 30 to 50, affecting both men and women equally. But it can also start in childhood. The skin disease (psoriasis) and the joint disease (arthritis) often appear separately. In fact, the skin disease precedes the arthritis in nearly 80% of patients. The arthritis may precede the psoriasis in up to 15% of patients.