Scientists hope adding vitamin D to the diet could help prevent one of the most common and painful forms of arthritis.
Over one million in UK have osteoarthritis
Osteoarthritis affects more than a million people in the UK, many of them elderly.
There is currently no cure and all doctors can do is control pain and keep patients active and mobile.
With the growing number of elderly people and better life expectancy, the number of people with osteoarthritis is expected to soar over the next five years.
But scientists at the Royal National Orthopaedic Hospital (RNOH), in Stanmore, Middlesex and University College, London, are to study 600 patients to see if they can help prevent osteoporosis of the knee.
They will study the patients over a three-year period to see whether a simple tablet or supplement can help prevent cartilage destruction and reduce pain.
We hope that by preventing the progression of the disease, patients will experience less joint pain from their arthritis
They will measure the effects on the cartilage with X-rays.
Dr Richard Keen, the consultant rheumatologist at the RNOH in charge of the trial said: "We hope that this study will bring real improvement to the lives of patients with osteoarthritis.
"We hope that by preventing the progression of the disease, patients will experience less joint pain from their arthritis.
"Supplementation with Vitamin D may also have other health-related benefits, and we hope to be able to assess these during the study period."
Earlier data from American studies has suggested low levels of Vitamin D in the blood are associated with more wear and tear in the joint cartilage at the hip and knee and this would lead to a more rapid progression of the disease.
The Arthritis Research Campaign has funded the study with a £500,000 grant.
A spokeswoman said:"Sometimes the simplest things are the most effective.
"We're already running a big clinical trial to find out if losing weight can help reduce knee pain, and a separate study investigating whether cod liver oil has a similar effect.
"The Vitamin D trial is another common sense way to practically help people with osteoarthritis of the knee, until a cure can be found in the long term."