Shoes with high heels are the fashion choice many women the world. However, a new study proves that wearing high heels a long period time can permanently injure the body. The study is Stanford University the USA. A team of biomotion researchers did tests the knees of women when they walked in flat shoes, shoes with 3.8-cm heels and in shoes with 8.9-cm heels. The results send a warning women who want to wear high heels that they risk permanent damage their knees. They said high heels put knees an awkward, bent position that makes them function like aged or damaged joints. This increases the risk the condition osteoarthritis, which could require surgery. Britain's Daily Express newspaper reports a recent survey 1,200 women that shows how popular high heels are. It said 93 per cent women say they felt sexier and more feminine when they wore heels, 88 per cent said they considered themselves more stylish and 77 per cent said their heels made them feel slimmer. Many women prefer to ignore health warnings, and even the pain and discomfort wearing heels, to look and feel good. A British doctor, Tim Allardyce, said he regularly treats women problems caused wearing heels. He said: "The odd angle which the feet are held high-heeled shoes increases the downward pressure the knees by 25 per cent, placing significant stress the kneecaps."