DEAR DR. DONOHUE: I am a 37-year-old salesman who plays basketball twice a week during the season. I have done something to my knee. It hurts below the kneecap. If I lay off playing for a week, the pain is just about gone. It returns if I start playing again. One of my teammates says I have jumper’s knee. What is it, and what can I do for it? Another thinks I have cracked the kneecap. Could that be true? – J.W.

ANSWER: Jumper’s knee is an inflammation of the tendon that links the upper leg bone – the femur – with the lower leg bone – the tibia. The kneecap is embedded in that tendon. Inflammation causes the collagen fibers of the tendon to degenerate. They are replaced by scar tissue.

The pain of jumper’s knee often starts off as a diffuse pain over the entire front of the knee. With the passage of time, it settles in a spot that a person can point to with one finger. That spot is below the kneecap.

It’s landing from a jump that creates the tendon inflammation. The force of landing can amount to 10 times the jumper’s body weight. The tendon of an untrained athlete – and I hate to imply that you are untrained – cannot withstand such repeated force. The collagen fibers fray and give way.

Do you find that your knee hurts when you go down the stairs or when you lower yourself into a chair? People with jumper’s knee usually complain of pain when they execute these movements.

Treatment is rest, and it can take four to six weeks of rest before a person can participate in sporting activities without pain. Anti-inflammatory medicines like ibuprofen help.

Once the pain has gone, the prevention for jumper’s knee is building the quadriceps muscles – the front thigh muscles. Weight training is the best way to achieve this, but don’t attempt it until your knee is pain-free.

If your knee continues to hurt after a week’s rest, you must see a doctor. There are too many knee problems that create similar pain but require quite different treatment. I don’t believe you have cracked your kneecap. It happens, but your story doesn’t fit the usual picture of such an injury.

DEAR DR. DONOHUE: Is it possible to build a muscle even if you’re not sure there is a muscle there? I am talking about my calf muscles. I know this is something hereditary, because my three sisters and I have no calf definement. Is there any hope for us? What can give us some calf muscles? – C.L.

ANSWER: I can assure you that you and your sisters have calf muscles. You wouldn’t be able to walk if you had none.

You might not have the well-defined muscles of bodybuilders, but even some of them have trouble increasing the size of their calves and resort to implants. Don’t even think about doing that.

The rise-on-toes exercise is a calf-muscle-builder. To get the hang of how it’s done, stand on a stair with your heels jutting off the stair. Rise up on your toes and then lower yourself slowly until the heels are well below the level of the stair. Be sure to support yourself by holding onto a railing. Repeat the exercise 10 times, take a break and then do two more sets of 10 rises and lowerings with a rest between sets.

DEAR DR. DONOHUE: When I swim in the ocean or a lake, I can swim forever without becoming breathless. When I swim in a pool, I struggle after two or three laps. Could this be due to chlorine? – R.H.

ANSWER: It could be. Experts have found that heavily chlorinated water causes airway constriction in sensitive people. Pool water has to be chlorinated to keep it free of germs.

Ask the people in charge of the pool what the water chlorination level is. Regulations call for it to be 1 to 3 ppm (parts per million). If it’s heavily chlorinated, that could be your problem.

DEAR DR. DONOHUE: Does being put on blood pressure medicine mean you take it for the rest of your life? I have just started taking such medicine, and I don’t like the idea of having to take it forever. Is there some other way to control blood pressure? – J.H.

ANSWER: Weight loss and exercise can lower blood pressure. So can limiting salt. Keep in mind that most of the salt we eat comes from salt in processed foods and not from the saltshaker, so you have to look at the salt (sodium) content of all foods.

Adopting the DASH (Dietary Approaches to Stop Hypertension) diet can bolster your chances of becoming medicine-free. When followed to the letter and if blood pressure is not off-the-chart high, this diet can sometimes lower pressure as effectively as drugs. The diet emphasizes complex carbohydrates, fruits, vegetables and low-fat dairy products while de-emphasizing fats and meats. Complex carbohydrates are things like pastas and starches. Simple carbohydrates are sugars.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.