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Our reader, above, belongs to two groups of people - soldiers and athletes - who are liable to develop early osteoarthritis. Glucosamine, available as a food supplement, has been a popular remedy to treat or prevent osteoarthritis for 50 years and no doctor can fail to have had patients who haven't sworn by its effectiveness.

Glucosamine is made from fish shells but it can be synthesised in the human body as it is present in cartilage, tendons and ligaments. With age this ability to synthesise glucosamine begins to deteriorate, just at a time when joints are beginning to show the effects of wear and tear.

For many years claims made for glucosamine were either dismissed out of hand or accepted with a superior smile and the suggestion that it was unlikely that taking it would do any harm. To most doctors' surprise, various reports of trials carried out over the past 10 to 15 years, and published in reputable journals, have not dismissed the use of glucosamine.

Early fears that glucosamine might have adverse effects in diabetic patients, as it has a role in glucose metabolism, have not been borne out except in occasional cases. Recently William Ransom, one of Britain's oldest pharmaceutical companies, started producing glucosamine, marketed as Alateris, to the standards and quality control demanded in pharmaceutical products and available on prescription.

Several surveys have shown that glucosamine is superior to a placebo in the treatment of mild to moderate osteoarthritis of the knee. Patients who have impaired glucose tolerance or raised cholesterol levels are advised to have their bloods checked regularly if taking glucosamine, and it is not recommended for people on anticoagulants. The obvious danger is shellfish allergy, but otherwise its listed side-effects are relatively mild and commonly affect people not taking any drugs. They include such problems as headache, tiredness, abdominal pain and indigestion.