Who can resist the allure of a piece of cushioning designed to slip under a belligerent foot and correct posture? Or the lingering appeal of knee strapping? Ah, orthotics! Even the word - which literally means anything designed to straighten, but is more generally used to describe a device used to try to correct a bony problem - is fragrant with healing and the promise of a better life through well-fashioned technology.

For those who suffer from pain in their knees - we're not talking arthritis here, or anything more serious, but the crackles, aches and pains that are common in people who are fit and active - there's something boundlessly reassuring about applying an orthotic device. Painkillers offer a certain satisfaction, it's true, but orthotics are your longer-term friends. If you have them strapped to your knee and you are wearing shorts then they are like medals. "Here's an athlete!" they scream. "Admire me! Sympathise with my pain!"

It would be nice if we knew whether orthotic devices work. To a large extent, unfortunately, we don't. A search found 15 relevant trials of foot and knee orthotics of which only five were deemed worthy of attention - none of which looked at insoles. Despite being the very best available, the five trials were short, poorly designed and didn't include many people. They didn't adequately blind people to whether they were receiving a proper device or a placebo one. They didn't randomly allocate people in a way likely to minimise a biased outcome. As human scientific endeavours, they were rotten failures. We still don't know if orthotics work.

Which isn't to say that it's beyond our mental power to hobble along to Boots and purchase whichever form of strapping or insole most appeals to us, then shove it on and see if it makes us feel better. There's insufficient evidence to protect us from a placebo effect, but if our knees feel more youthful and we have got more bounce then we will probably not complain.

When we are talking about treatments that are expensive, deceitful or dangerous, a lack of good trial evidence should stick in our throats. For those that are cheap and relatively cheerful, and that no one is selling to us as though they were proven cures, we can afford not to get angry. Want to know if orthotics are going to help your knee pain? Try them and see.