DEAR DR. DONOHUE: I have osteoarthritis, which, I’m told, comes from aging. If that is so, why don’t all my friends have it? I am 77. What’s the best medicine for it? How about joint injections? – C.C.

ANSWER: Osteoarthritis – also called degenerative arthritis – is the No. 1 kind of arthritis. Age is a factor in its onset, but it is far from the sole factor. Something not yet clearly evident changes the composition of the cushioning cartilage within joints, and that something brings on arthritis.

A joint is the juncture where the ends of two bones meet. Cartilage covers the bone ends to allow them to bend and twist against each other smoothly and painlessly. With osteoarthritis, the cushioning cartilage frays and flakes, and cells within the cartilage produce enzymes that can fill the joint with fluid.

Medicines are not the only focus of treatment. Exercise is most important. It keeps involved joints limber, and it strengthens adjacent muscles. Strong muscles stabilize joints and protect them from further damage. An exercise program for osteoarthritis is one that is best learned from a professional – a physical therapist. Occupational therapists can teach arthritis patients what devices are available to facilitate joint motion and how patients can use those devices.

Medicines abound. A simple pain reliever such as acetaminophen (Tylenol) might be the only drug needed. If stronger medicine is called for, anti-inflammatory, painkilling drugs like Aleve, Indocin, Voltaren and Motrin can often bring relief. These drugs have the potential to irritate the stomach. If they do, anti-inflammatory drugs without such stomach irritation can come to the rescue. Celebrex, Vioxx and Bextra are the names of those medicines.

Joint injections with cortisone can be given every three months. Such injections are valuable when drugs are not dulling the pain and when the joints are filled with fluid.

DEAR DR. DONOHUE: I am on my second stye. What’s causing them? I let the first go without any treatment, and it got better. Should I do the same with the second one? – R.G.

ANSWER: Styes are infections of the eyelash follicles or of eyelid glands. The staph germ is the usual cause.

The red bump of a stye is so common that there’s no need to belabor a description of one. A stye is tender to the touch.

One universal treatment for a stye is a warm compress. A washcloth soaked in warm water will do. Hold it on the stye for 15 minutes four to six times a day.

That brings the stye to a head and promotes spontaneous drainage of the pus inside it. Drainage is the ultimate stye treatment.

Don’t squeeze styes to promote drainage. Squeezing creates trouble. It can spread the staph germ into neighboring tissues. Use compresses on your second stye, and you should see it resolve more quickly than the first one did.

If styes keep coming back, your doctor can prescribe antibiotic eye ointments that eradicate lingering staph germs.

DEAR DR. DONOHUE: What’s the difference between synthetic vitamin C and natural vitamin C? I am quite health-conscious, and I keep current on nutritional matters. I have read that the synthetic vitamin C is worthless. Do you agree? – R.Z.

ANSWER: No, I don’t agree. Synthetic vitamin C – man-made – is just as effective as natural vitamin C. I don’t bother looking to see if the vitamin C that I take is synthetic or natural.

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.