According to medical definitions, there are more than 40 conditions that manifest as joint pain. The most likely causes are joint injury, joint strain or sprain, infections, cancer and inflammatory joint disease such as the various types of arthritis. Tendonitis and bursitis can also fit into these categories.
Here, we will concentrate on the inflammatory conditions that cause joint pain, the most common form being the condition we all know as arthritis. The word comes from arthro (joint) and itis (inflammation) and inflammation is defined as the symptoms of heat, pain, redness and swelling. Sound familiar? Arthritis, however, is a much more complex and diverse condition than you might at first imagine.
Arthritis in its many forms is America's major cause of disability and chronic pain. It affects 16.7 per cent of Americans (more than 3.4 million people), of which 60.4 per cent are women. Sixty per cent are between the ages of 15 and 64 (ie of working age). Fifty-four per cent of Americans over 75 have arthritis.
Arthritis is a general term for many conditions, of differing causes, involving inflamed, thickened and/or painful and stiffened joints. There are at least 100 known types of arthritis, but only five of these account for 90 per cent of cases. The main ones are classified generally into three groups:
• Osteoarthritis (OA).
• The systemic inflammatory forms of arthritis such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and fibromyalgia, which frequently has an infective trigger. These are often autoimmune diseases.
• Gout.
Osteoarthritis is the most common type of arthritis and is a localized disease that involves increasing deterioration of the cartilage in the joints caused by injury, repetitive use or general wear and tear. It typically runs in families and is three times more common in women than in men.
The structure of the joint is composed of hyaluronic acid, proteoglycans attached to glycosaminoglycans. In the joints, cells called chondrocytes make and maintain the integrity of the cartilage. These cells receive nutrients from the synovial fluid, which also removes waste byproducts. The synovial activity is triggered by movement, which compresses and releases the sponge-like cartilage.
Osteoarthritis is characterized by the degeneration, destruction and erosion of the cartilage in the joint, with bony outgrowths (Hebderden's Nodes) often forming at the edges of the joints. The synovial fluid changes and the elasticity of the cartilage degenerates. The joint surfaces become irregular, flattened and poorly adjusted to each other. This causes the joint cavity between adjacent bones to narrow until eventually the cartilage disintegrates and the bones may directly scrape against one another.
Osteoarthritis is more common in weight-bearing joints such as the ankles, knees, elbows, wrists, spine and shoulder (wear and tear) and is commonly one-sided: for example, in the right thumb in right-handed people. Osteoarthritis gradually develops over several years and initially is not always painful, although in the later stages when the cartilage has disintegrated, inflammation sets in and muscle spasms may occur. Many older people have difficulty looking after themselves as their movement is restricted by severe pain and stiffness.
Although the specific triggers for osteoarthritis are unknown, it may be precipitated by excess salt consumption, which affects calcium metabolism, and obesity, which causes greater wear and tear. Because of the joint destruction that occurs, osteoarthritis is better for rest and worse for movement, as movement (particularly weight-bearing) increases the damage. Movement causes the joints to scrape together and increases the inflammation. Despite this, exercise is vital, so non-weight-bearing exercise such as swimming is excellent.
