Just How Bad Are Sandals for Your Feet?

Danger ranking: 2. Brenner says these were a lifesaver when she had to stand all day during her residency. But they're not stable enough for distance walking, and a small study in Arthritis Care & Research suggests that that they may not be a good bet if you suffer from osteoarthritis of the knee, as the study found that they increased the load on knees by up to 15 percent compared with flat walking shoes with flexible soles, flip-flops or going barefoot.

Best for: Swaying at a mellow concert; preparing hors d'oeuvres for a party

Avoid: Sightseeing around Europe

Doctor's note: "If you're going to be doing a lot of walking, your best bet, really, is a pair of stylish athletic sneakers," says Brenner.