If you’ve ever been stopped cold by a charley horse, you know just how excruciating these muscle spasms can be. But are you sure it’s just a muscle spasm? Or is that leg pain due to something far more serious?

What can cause leg pain…

PERIPHERAL ARTERIAL DISEASE (PAD)

This is one to worry about. Even though the pain usually isn’t intense, it can triple your risk of dying from a heart attack or stroke.

What it feels like: About 10% of people with PAD suffer leg cramps, leg aching and leg fatigue that occur only during physical activity involving the legs (any type of activity can trigger it—even just walking). When you rest your legs, the discomfort goes away, usually in 10 minutes or less. As PAD becomes more severe and blood circulation worsens, pain can occur during rest and result in leg ulcers and even gangrene.

What to do: See a doctor. PAD is usually caused by atherosclerosis, the same condition that leads to most heart attacks. Your doctor will compare the blood pressure in your arms to the pressure at your ankles. If there’s a significant difference, that could mean that you have PAD and you’ll need an ultrasound of the legs to determine the extent and location of arterial obstructions.

Next steps: The same practices that protect your heart—such as not smoking, controlling diabetes, maintaining healthy blood pressure and getting plenty of exercise—will help stop PAD from worsening and could even reverse it.

Important: You must walk—even when it hurts. Walking ultimately reduces pain and improves circulation by stimulating the growth of blood vessels that bypass the damaged ones. With your doctor’s OK, walk five times a week, for 30 to 45 minutes each time. I usually advise my patients to walk fast for two blocks or until they feel moderate pain, then rest a moment and walk fast for two blocks again, repeating until the end of their workout.

DEEP VEIN THROMBOSIS (DVT)

It doesn’t always cause leg pain, but if pain occurs, this warning could save your life. DVT means that you have a blood clot—most often deep in a leg vein. It can be fatal.

What it feels like: You might notice a sudden, pulsating or aching pain deep in your calf or thigh, sometimes accompanied by redness and/or swelling. DVT usually occurs after you’ve been immobile for a long time—you’re laid up in bed after surgery, for example, or following a long car or plane trip.

What to do: Get to an emergency department or a physician’s office where you can get an immediate ultrasound. The clot could break free, travel to the lungs and cause pulmonary embolism, a clot in the lungs that’s fatal in up to 30% of cases.

If you have a DVT, your doctor will probably give intravenous or injectable heparin, a blood-thinning drug that prevents the clot from growing. After a day or two, you’ll be switched to oral blood-thinning medication, such as warfarin (Coumadin) or dabigatran (Pradaxa). You’ll need to take the medication for about six months. If the clot is not entirely dissolved after treatment, it should be monitored with ultrasound—and if you have had one clot, you might get another one.Prevention is critical.

Everyone—whether you’ve had a DVT or not—should flex the ankle and calf muscles for about 30 seconds every 20 or 30 minutes when sitting for longer than four hours. Stand up and move around at least every hour or so.

If you have risk factors for blood clots—you’re over age 40, obese, have a family history of blood clots or use hormone replacement therapy—ask your doctor about such precautions as taking aspirin before travel and/or wearing compression stockings while you’re immobile.

SCIATICA

This back condition is typically caused by a herniated spinal disk. The legs become involved because the disk exerts painful pressure on the sciatic nerve, which runs down the backs of the legs.

What it feels like: Intense, shooting and/or knifelike pains may extend through the buttocks and into one leg. Sciatica also can cause leg and/or ankle weakness.

What to do: See your doctor. If you do have sciatica, you may get better within eight weeks by doing physical therapy and using a nonsteroidal anti-inflammatory medication such as ibuprofen(Motrin)—90% of sciatica patients do.

Next steps: Consider surgery for a herniated disk/sciatica only when the pain is too intense to handle…you have responsibilities that don’t permit extended downtime…or you’re having additional symptoms such as muscle weakness or a loss of bowel/bladder control.

When It Really Is a Charley Horse

A muscle spasm, including the infamous “charley horse” of the leg, believed to have been named after a lame horse, can occur after hard exercise or for no obvious reason. It can cause sudden, localized pain (usually with sharp contractions) that often hits the calves.

If you’re getting muscle spasms with any sort of regularity, see your doctor. Muscle spasms have a variety of causes—for example, you may have overworked your legs by doing yard work…you may be dehydrated (without enough water, muscle cells can spasm)…or a medication you’re taking, such as a diuretic, may be the culprit.

Helpful: Because most muscle spasms are caused, in part, by tight hamstrings (the muscles in the backs of your upper legs), I recommend doing a standing hamstring stretch on a regular basis. Start in a standing position with your knees straight…bend at the waist…and reach for your toes or the floor until you feel a stretch in your hamstrings. Hold for a few seconds, and repeat a few times a day.