While flip-flops do provide the wearer with some protection from hazards on the ground, such as hot sand at the beach, glass, thumb tacks or even fungi and wart-causing viruses in locker rooms or community pools, their simple design is responsible for a host of other injuries of the foot and lower leg. In the United Kingdom in 2002, 55,100 individuals went to hospital with flip-flop related injuries. By 2010, there were 200,000 flip-flop related injuries costing the British National Health Service £40 million.
Walking for long periods in flip-flops can be very tough on the feet, resulting in pain in the ankles, legs,and feet. A 2009 study at Auburn University found that flip-flop wearers took shorter steps and their heels hit the ground with less vertical force than those wearing athletic shoes.
The lack of support provided by thong sandals is a major cause of injuries. Since they have a spongy sole, the foot rolls further inward than normal when it hits the ground — an action called over-pronation, which is responsible for many foot problems. Over pronation may also lead to flat feet. Flip-flops can cause a person to overuse the tendons in their feet, resulting in tendonitis. The lack of an ankle strap that holds the foot in place is also a common reason for injury, as this causes wearers to scrunch their toes in an effort to keep the flip-flop in place, which can result in tendonitis.
Ankle sprains or broken bones are also common injuries, due to stepping off a curb or tumbling — the ankle bends, but the flip-flop neither holds on to nor supports it. The straps of the flip-flop may cause frictional issues, such as rubbing, during walking. The open-toed nature of the thongs may result in cuts, scrapes, bruises, or stubbed toes. Despite all of these issues, flip-flops do not have to be avoided completely. Many podiatrists recommend avoiding the inexpensive, drug store varieties and spending a little bit of extra money on sandals with thick-cushioned soles, as well as ones that have a strap that’s not canvas and that comes back almost to the ankle.