What it feels like: Throbbing pain and usually swelling in the foot or ankle that progressively worsens the more you walk on it.
Is it serious? No, but see an orthopedic surgeon if you're experiencing these symptoms.
What causes it: A stress fracture is a tiny crack in a bone that may or may not show up on an x-ray. "When it comes to walking, small, repetitive forces fatigue the bone," says Dr. Donley. When one becomes overloaded from absorbing the impact of your feet hitting the ground, it literally breaks. Women over 40 are more prone to stress fractures, thanks to bone density issues.
How to prevent it: Up your mileage gradually so your skeleton can sustain long treks. Practice good bone health by getting enough calcium and Vitamin D in your diet, and make sure your walking shoes have good shock absorption—another reason to take extra care when selecting sneakers.
How to treat it: More rest: Stress fractures typically require you to take four to six weeks off the injured foot to heal completely. Depending on the severity of the injury, you may be put in a cast or walking boot. When you start walking again, your doctor may advise you to wear an orthotic for additional support. In rare cases, surgery is needed to insert pins that help the fracture heal.