Flip-flops may be fashionable, but they can cause foot problems

Sam Hobert, 19, has suffered for his flip-flops. A few years ago, he broke his right big toe after slamming his foot into a rock while hiking in New Hampshire in his favorite summertime footwear. On a warm day a few weeks ago, the George Washington University freshman was nursing foot blisters, courtesy of a pair of new brown leather 'flops.

It's springtime and flip-flops — the airy sandal with the distinctive thwack-thwack soundtrack — are back, much to the frustration of podiatrists. Wearing flip-flops can cause problems ranging from stubbed toes and cuts to overuse injuries such as foot stress fractures.

Now that the weather is warmer, says Howard Osterman, a podiatrist who has practiced in Washington for 20 years, he will see at least one patient with a flip-flop injury every day through September.

The No. 1 problem he sees from the shoes are overuse injuries such as stress fractures of the metatarsals, the five long bones that reach out to the toes. A stress fracture happens after constant, repetitive stress to a bone and is generally treated with rest, more-supportive shoes and perhaps a walking boot.

Many of the less-expensive flip-flop styles consist of just a flat piece of rubber and the toe thong. The lack of arch support can cause another common foot injury: plantar fasciitis, inflammation of the thick band of tissue along the bottom of the foot that causes a stabbing pain, especially in the heel. People with flatter arches are more prone to such overuse injuries because they need more support for their muscles and ligaments, Osterman says.

Flip-flops also leave the feet unprotected and exposed to the elements, which can mean cold toes, sunburns, cuts and bruises.

In 2008, Justin Shroyer, a biomechanics graduate student at Auburn University in Alabama, studied 39 college-age men and women to see how they walked when wearing flip-flops compared with sneakers. Shroyer, now an assistant professor at the University of Louisiana at Lafayette, found that while wearing flip-flops, participants in his study took shorter steps. He hypothesized that this was because the wearer was trying to get his or her foot on the ground faster, to prevent the shoe from flying off. Also, flip-flop wearers did not bring their toes up as much during the leg's swing phase because they tended to grip the sandals with their toes.

"Your toe flexors are fighting what you're naturally trying to do," Shroyer says. "It's kind of an antagonistic push-pull, tug-of-war going on, and it's not happening in running shoes or bare feet."

The researchers speculated that the altered gait could result in pain from the foot up into the hips and lower back.

A 2010 study by Rush University Medical Center in Chicago found that flip-flops and sneakers with flexible soles were easier on knees than clogs or special stability shoes. The researchers analyzed the gaits of 31 people with osteoarthritis of the knee while they wore the various types of footwear.

Osterman doesn't suggest avoiding flip-flops entirely, but he says that people should wear them in moderation — for a few hours on the beach or at the movies, for example.

Shoppers should look for flip-flops with a stable sole, he says. Brands such as Reef, Rainbow, FitFlops, Teva and Merrell make models that throw more of the weight into the heel and out of the forefoot, he says.

"When you only have something between your toes to keep the shoe on, you have to curl your toes excessively," Osterman says. "You have to spend all day firing your muscles to keep the shoe on the foot."