I am training for a marathon and I run about 30 miles a week. A long run for me is about 12 miles. For the past month, I have developed pain in my legs right above the ankles. One day the pain was so bad I had to stop running after only 2 miles. What could be causing this?

The pain you experienced in your lower legs could be the result of several conditions. Stress fractures are very common among runners with the symptoms you describe. Usually they occur in the proximal or distal thirds of the leg. Localized pain, swelling, increased warmth and point tenderness are present. Other causes of lower leg pain include tendinitis or inflammation of the outer soft tissue covering a bone called the periosteum. Exercise-induced compartment syndrome is another condition that causes soreness and tenderness in the muscle groups of the lower leg after running. Pressure builds in the compartments that contain different muscle groups. The pain usually subsides and the pressure dissipates when you stop running. Sorting out the cause of lower leg pain in runners is sometimes challenging. Reviewing changes in training schedule, evaluating running surfaces and shoe wear is important. Observing the individual walk and run to spot excessive pronation (in-turning of the foot) can help to provide clues as to the source of symptoms. If X-rays fail to identify the problem, more sophisticated tests, such as a bone scan or magnetic resonance imaging scan (MRI), are required to make the diagnosis.