DEAR DR. DONOHUE: I'm a baseball mom who got hit in the leg by a bat. The aching just wouldn't go away. My doctor said I had a vein clot and put me on blood thinner. How long will recovery take? I am 51, overweight, although my cholesterol is fine. The doctor says the clot is in a deep vein and is a risky deal. Can you elaborate? - Mrs. J.O.

ANSWER: Forget cholesterol here. It has nothing to do with it.Vein clotting often begins with a blow to the leg that injures the vessel. Platelets, clotting substances in the blood, rush to the scene to protect the vessel, in this case too ambitiously. The platelet onslaught leads to the clotting. The name for the condition now is thrombophlebitis (thrombus, a clot; phlebitis, vein inflammation). Large veins deep in the leg tissue are most likely to be affected.

Meanwhile, the threat of another more ominous outcome arises - that of pulmonary embolism. That's when a bit of the clot breaks loose and drifts into lung circulation, where it can do serious damage, often with dire, even fatal, results.

The aim of blood-thinner medicine is to prevent clot growth and close off the embolus threat. While the pain may last only a month or two, the thinner is usually given for much longer to prevent a recurrence of clotting.

Meanwhile, you should avoid prolonged standing or sitting, elevate your legs for 30 minutes at least three times daily, and use elastic stockings.

DEAR DR. DONOHUE: My sister called me excitedly about some medical news she heard. It was that fasting helps those with arthritis, which I have. I am writing to ask what you think about this idea. - K.S.

ANSWER: In a few preliminary studies, some arthritis patients did seem to benefit from short-term fasting. But I certainly wouldn't want you trying it until much more evidence has accumulated to confirm positive effects. For now, I think you'd have to say that the known ill effects of unwise fasting far outweigh any yet uncertain benefits.

DEAR DR. DONOHUE: What is IHSS? How do you get it? - V.M.

ANSWER: Without completely untangling all the medicalese, let's just say that IHSS (idiopathic hypertrophic subaortic stenosis, if you need to know) is heart muscle enlargement. It is inherited in at least half of the cases, and when it appears without a genetic history of it in a family, it gets the name "idiopathic" - cause not known.

People with IHSS can develop seriously abnormal and life-threatening heartbeats, especially during exercise. In fact, it is sometimes the cause of the tragic incidents of young, apparently healthy athletes dropping dead during vigorous competition. That's why steps should be taken by those with IHSS to avoid such situations and to have close relatives examined for the condition.