Abstract
Up to 150 different diseases can affect the joints and musculoskeletal system. These range from musculoskeletal rheumatism, which is self-limiting and causes no demonstrable joint pathology, through metabolic and degenerative joint diseases to the chronic auto-immune disorders of inflammation of which rheumatoid arthritis is the most common in the United Kingdom, and the most severe. Many of these conditions are characterised by inflammation which has the cardinal symptoms of heat, swelling, pain, erythema, and loss of function. Rheumatologists require accurate and objective methods of measuring all these parameters at a large number of joints, each of different anatomical structure, in order to adequately monitor the course of the disease and its response to treatment. Complementary information is required on the function of muscles, ligaments, tendons, and bone, as well as the joints. Although the individual analysis of each of these components is likely to provide the most information on disease pathogenesis, functional evaluation which integrates many of these variables simultaneously is likely to provide most information on the patient's progress. Both are needed. In the realm of therapeutics, a wide range of prostheses, all of sound bioengineering design, are available. Greater problems arise in the matching of different prostheses to an individual patients needs and in their fixation in a patient whose disease is constantly altering the joint contour. The attention of bioengineers is now being directed towards the design of replacements for other parts of the joint and musculoskeletal system, for example, ligaments. Adequate methods of testing these under repetitive stress and of measuring the improvement they provide will be increasingly required.