UGG boots have been a winterweather fashion for several years now, combining function, comfort, warmth and even some style. What many UGGenthusiasts don't know is that their boots are a breeding ground for bacteria and cause foot problems. Doctors believe the boots, which are particularly popular among young teenage girls, are leading to a rise in the number of people suffering pains in their feet and knees. Dr. Ian Drysdale, head of the British College of Osteopathic Medicine, believes because the foot does not get the proper support on the inside, it will lead to more ankle, knee, hip and back problems. "These boots are not designed for outside wear. Just because something becomes a trend or fashionable doesn't mean it's good or right," he said. "The particular problem with this type of footwear is that it is unsupported. It's a slipper. You wouldn't normally expect to be doing outdoor activities from something that's indoor. If you decide to wear your pajamas outside all the time, someone will come up and say it's not a good idea." Dr. Drysdale explained that the feet issues become a particular problem among young teenage girls, whose bones are "plastic" and developing when they are growing. "If that structure is developing in an inappropriate way," he said,"then the ultimate structure will be _ ." Mike O'Neill, a consultant surgeon, said,"As the foot slides around, you get wear and tear    on the joints on the inside of the foot. The ankle is in the wrong position, the thigh bone also changes position, and you get an abnormal movement in the pelvis, which leads to back problems." UGG Australia, who makes the designer version of the boots, told The Daily Wirror that their boots are "comfort" rather than "performance" footwear and consumers should be aware of "knockoffs  " which lack reinforced heels in their boots. Teenage girls prefer to wear UGG boots because of the following EXCEPT   _  .
design comfort quality warmth