For many, flip-flops are the summer footwear of choice. They’re cool, they’re easy to slip on, they’re cheap, and they come in amazing array of colors and styles. But if you spend your summer in flip-flops, you may be doing not just your feet, but your whole body a disservice. Although slipping them on at the pool or the beach is probably ok, prolonged flip-flop wear can lead to a variety of problems.

Feet were designed to walk barefoot on natural surfaces, and modern inventions such as concrete and asphalt wreak havoc on them, making shoes a necessity. The primary purpose of shoes is to absorb the shock as your feet hit these immovable surfaces, and flip-flops just don’t provide the shock absorption or support of a proper shoe.

Most flip-flops offer no arch support whatsoever. They’re unstable, and slip and slide under your feet. In addition, to keep the shoes on, your toes must grasp them each time you take a step. All this combines to cause problems that begin in the feet but may affect your body all the way to your neck. The combination of excessive stress and overuse due to the toes grasping contributes to plantar fasciitis, a painful condition in which the plantar fascia in the sole of the foot becomes inflamed. The constant gripping can also cause leg pain.

Because flip-flops are unstable, they change your gait in subtle ways which can cause misalignment of the joints higher up in the body. This causes excessive wear and tear on the knees, especially if you’re carrying extra weight. You use muscles differently in flip-flops than when you’re wearing normal shoes or walking barefoot, and this can cause sprains, strains, repetitive injuries, and even misalignment of the spine. Poorly-fitting or unsupportive shoes are a common cause of back pain, and flip-flops are the epitome of poor fit and lack of support.

The feet are the foundation of the body, and just like buildings, an unsound foundation leads to an unstable structure. For optimum health of your feet this summer, choose a pair that has a thicker sole and some arch support. If you plan on wearing them a lot, consider spending a little extra money on an orthopedic pair. And if you experience foot, leg, or back pain, switch to more supportive shoes. Your feet—and the rest of your body—will thank you.