When Is Leg Pain Dangerous?

Marie Savard breaks down the signs and symptoms of DVT.

Sept. 23, 2008 — -- Sometimes leg pain is just a cramp, but it also can be a sign of a blood clot or deep vein thrombosis, which can be fatal if it results in a pulmonary embolism, which is when a piece of the clot breaks off and travels to the heart or lungs.

Up to 600,000 Americans have pulmonary embolisms each year and at least 10 percent of them die because it, according to the American Heart Association.

"Good Morning America" medical contributor Dr. Marie Savard tells you the warning signs of leg clots and what to do.

Who Is at Greatest Risk?

This is one disease in which knowing whether you are at risk makes all the difference. Women in particular are at risk, and women on birth control pills are at increased risk. Also if you have any of the following:

if you are extremely overweight;

if you've been sedentary for a long period of time for whatever reason;

if you've had surgery;

if you're in a cast;

if you've taken an unusually long plane ride;

if you are genetically predisposed to blood clots, which would include if you've had a blood clot previously, perhaps during pregnancy or after surgery or if a family member has had one.

What Are the Symptoms?

Half of the time there are no symptoms, which is why this is called a silent killer. It can be fatal when a blood clot travels from the leg to the heart. But the other half of the time, there are symptoms, though they are often subtle. It can be a cramp in one leg that does not go away, chronic swelling or unexplained redness or bruising.

If you have any of these symptoms, go to your doctor or the emergency room and insist on an ultrasound, which will immediately tell you whether you have a blood clot.

What to Do and Preventive Measures

There is a test with no needles or dyes. They tell you right away if you have a blood clot, so doctors should not hesitate to give you an ultrasound if you are high risk at all.

If you have a blood clot, especially the very dangerous ones above the knee, which are the ones that travel, you can be put on blood thinners, which are very effective at dissolving blood clots and taking care of this problem.

Preventing DVT depends on its cause. If it's genetic blood clotting, stay on blood thinners for life. If surgery or immobility is the problem, early ambulation will help and you should avoid bed rest.

Doctors frequently use small doses of blood thinners at the time of surgery to prevent them too.

Finally, if it's from air travel, get up and walk, pump your calves while you're in your seat or when standing.