ANY TIME Mr. O tried to walk, even a short distance, his left leg hurt. His calf felt heavy, and the only way to stop the pain was to stop walking. He couldn't even walk to his mailbox anymore.

Mr. O's symptoms had significantly changed his lifestyle. He could no longer walk his dog. He could no longer accompany his wife to the grocery store. On his recent summer vacation, he couldn't even walk on the beach with his grandchildren to search for shells, as he had done in summers past.

Mr. O was not elderly. He was 64 years old and, in his words, even though he was retired he was not ready to stop living.

The good news for the patient I'm referring to as Mr. O is that his condition is treatable. Mr. O has PAD--peripheral arterial disease. PAD is a disease that causes blockages, or stenoses, in the arteries supplying blood to the legs.

This same disease process causes heart attacks and strokes when it occurs in the arteries that lead to the brain or the heart.

The symptoms of PAD typically occur when walking, because when the leg muscles are working, they need more blood to support the added activity. If there are blockages in the arteries supplying the legs, this registers as muscle discomfort, heaviness or pain.

The symptoms are relieved upon resting. But just because the pain subsides doesn't mean the problem has gone away.

The blockages can occur anywhere from the pelvis to the foot, but most commonly, the main artery in the thigh is partially or completely blocked. The muscle bed supplied by this artery is the calf, which is why the pain is usually worst there. If the blockage is higher, the muscles of the thigh or buttock also can be affected.

In very severe cases of PAD, the patient can have chronic foot pain, non-healing sores on the foot or even gangrene. If PAD progresses unchecked, it can lead to a limb-threatening condition.

A SIMPLE TEST

Mr. O eventually saw his primary care physician, who suspected that his leg pain could be from PAD. The doctor referred him for a screening test to see if indeed his symptoms were from PAD.