The idea of grannies in trainers may not be as far fetched as it seems. New research at Bristol University suggests the well-padded shoes could work wonders for arthritis.
The key is in the heel. The extra thick padding provides the ideal 'shock absorber' as the foot hits the ground, so easing the pain.
'It is fairly obvious, really,' said Paul Dieppe, professor of rheumatology at the university. 'We know that impact loading is the sudden high-velocity force which goes through your bones or joints when you hit your foot to the ground or jump, and that is just the type of mechanical force most likely to injure the tissues, the cartilage or the lining of the joint.
'We also know that if you wear shock-absorbing insoles you can reduce the peak strike force very considerably. What we have found, not scientifically but merely by prescribing to a lot of patients, is that many people feel much more comfortable wearing shoes with that type of insole.'
Professor Dieppe and his team of 20 are now trying to find the best type of shoe or insole to help the 1.5 million people in Britain - most in their fifties or over - who suffer osteoarthritis of the knee.
'We need to follow up lots of patients very carefully for a long time and, of course, trying to control people's footwear and figure out what sort of forces are going through their legs in their daily life is fabulously difficult,' he said.
None the less, Professor Dieppe, who has researched arthritis for 15 years, hopes to have more information within the next year. 'We are accumulating data on the progression and outcome of arthritis all the time. We get little bits of data to add to what we know and we hope to have a much more accurate picture on the trainer,' he said.
His research has also debunked the idea that arthritic joints need to be rested. Sensible exercise appears to be much better for them. 'This is fairly new, based on research, some with animals and a lot in the laboratory,' Professor Dieppe said.
'It basically shows that the cartilage, the weight-bearing surface of the bone which the joints work on, needs regular movement and loading in order to maintain its integrity.
'If you rest the joint you can actually very quickly get loss of substance from the tissue and changes in it which can be very harmful. What we worry about particularly is that if people rest up quite a lot they get loss of tissue from the cartilage and it gets weak. If they then suddenly do a lot of exercise, that is probably very damaging.'
Professor Dieppe recommends ordinary, everyday exercise such as walking and, for the more energetic, swimming, golf and cycling. Such a pattern of exercise fits neatly into people's general health, he said. 'This exercise is good for your cardiovascular health as well as your muscles and joints, and it is good for your bones.
'What we are a talking about is the concept of locomotor health, which is parallel to cardiac health. A healthy heart means keeping thin and having a sensible diet and regular exercise throughout your life.
'Now it looks as if locomotor health - muscles, bones and joints - works on exactly the same principles. Do regular exercise and keep yourself fairly trim in weight and you will maintain locomotor health and reduce the risk of joint disease, just as you do for heart disease.'
Professor Dieppe said the concept was new because researchers had only 'fairly recently' realised the capacity of joints to repair themselves.
'We, like the rest of the world, used to think that joints wear out and can't repair themselves, and that is absolutely wrong. The joint has a wonderful capacity to repair itself and keep its integrity throughout your life - as long as you keep to normal activities.
'This has really shown itself to researchers of late, and we are trying to apply these principles to the long-term locomotor health of the population. This is important because more than 10 per cent of people over 65 are in trouble with arthritis, and a lot of it is preventable.'