There are three main types of damage that occur to the musculo-skeletal system; the first is a sudden injury or sprain which might be a domestic injury, or might be incurred during a sporting activity or in a car accident. This usually causes local pain and bruising lasting for a few days, or even a few weeks. The other main group is arthritis and this can be divided into two important types, Osteoarthritis and rheumatoid arthritis.

Osteoarthritis is by far the commoner type of arthritis and can be thought of as 'wear and tear' damage to a joint. It usually occurs in older people and tends to affect the spine (both neck and lower-back), the hips, knees, elbows and shoulders. Nobody is clear about the exact cause of Osteoarthritis; it can sometimes run in families or it may result from severe localized damage in earlier life, such as a broken bone. Osteoarthritis tends to develop in one or two of the main weight-bearing joints of the body, but it does not usually affect all the joints of the body. The pain caused by osteoarthritis fluctuates; if a person suffers from osteoarthritis of the knee there will be periods when the knee is painful, and other times when the pain is less severe.

The X-ray of an osteoarthritis joint looks ragged and shows some joint destruction, but such X-ray findings do not correlate with the pain suffered. If joint destruction is demonstrable on the X-ray the patient may not have severe pain, and conversely the patient may have severe pain with few X-ray findings. The main problem with osteoarthritis is pain, which in turn causes a general lack of mobility and limited joint movement.

Rheumatoid arthritis is far less common than osteoarthritis and represents a completely different disease process. The small, non-weight-bearing joints in the hands and feet are affected by an active destructive process. This process is poorly understood and can occasionally result in joint deformity.