Arthritis (‘arth’ meaning joint, ‘itis’ meaning inflammation) isn’t a one-note story or even a few variations on a single theme; it actually consists of more than 100 different conditions.
These can be anything from relatively mild forms of tendinitis (as in ‘tennis elbow’) and bursitis to crippling systemic forms, such as rheumatoid arthritis. There are pain syndromes like fibromyalgia and arthritis-related disorders, such as systemic lupus erythematosus, that involve every part of the body. There are forms of the disease, such as gout that almost nobody connects with arthritis and there are other conditions – like osteoarthritis, the misnamed ‘wear and tear’ arthritis – that a good many people think is the only form of the disease.
True, many older people do have arthritis, but it’s not just a disease of the old. Some forms of arthritis affect children still in diapers, while thousands of people are stricken in the prime of their lives. The common denominator for all these conditions is joint and musculoskeletal pain, which is why they are grouped together as ‘arthritis.’ Often that pain is a result of inflammation of the joint lining.
Inflammation is involved in many forms of arthritis. It is the body’s natural response to injury. The warning signs that inflammation presents are redness, swelling, heat and pain. These are the same kinds of reaction the body has to a sliver in the hand, for example. When a joint becomes inflamed, it may get any or all of these symptoms. This can prevent the normal use of the joint and therefore it can cause the loss of function of that joint.
Anatomy of a Joint
There are more than 100 joints connecting the body’s 206 bones. Most of the major bone connections in the body are joints designed to allow a broad range of motion. There are different kinds for different functions: ball-and-socket (hips and shoulders), saddle joints (which connect thumb to hand), hinge joints (fingers and knees) or pivot joints (wrists).
Tied together by ligaments, the bones of joints are capped with a smooth substance called cartilage. This tough elastic material acts as a shock absorber and allows the bone ends to glide smoothly across each other. If the cartilage is destroyed (as in osteoarthritis), the bones of a joint can grind against each other causing pain, loss of mobility, deformity and dysfunction.
Between the bones is a joint cavity, which gives the bones room to move. The joint space between two bones is enclosed by a capsule that’s flexible, yet strong enough to protect the joint against dislocation. The inner lining of this capsule, the synovium, produces a thick fluid that lubricates and nourishes the joint. In many forms of arthritis, the synovium becomes inflamed and thickened, producing extra fluid which contains inflammatory cells. The inflamed synovium and fluid can damage the cartilage and underlying bone.
No one knows what causes arthritis, though scientists have uncovered a host of clues. Something can be done to manage most forms of arthritis, but it’s very important that a correct diagnosis is established early. Most therapies work best when started early in the disease process. You can read more specific information under Types of Arthritis.