Muscles act as shock absorbers when doing physical activities. When a muscle gets too worn out to absorb a shock, the shock transfers to the bone and can cause a stress fracture. Stress fractures are often caused by greatly increasing activity quickly, doing an unfamiliar activity, or using unfamiliar or improper equipment such as moving from running on a trail to running on pavement.
Stress fractures usually happen in the lower leg and foot.
Most stress fractures can be healed with rest, but severe ones may need surgery and hardware to hold everything in place. After surgery you may need to wear a cast or brace and you may have restrictions on your movement. Physical therapy and careful return to your exercise activities will make sure you're ok.