Prevention is a difficult topic when it comes to total joint replacement of the hip or knee. Too much of the damage is apt to be genetic or related to anatomical shape or injuries from long ago.

One thing that does make a big difference in joint wear and tear, though, is weight control. Excess weight puts stress on those joints — particularly the knees. So controlling it and exercising can reduce the chance that the joints that are essential for mobility wear out prematurely.

Replacement or repair of hips and knees is the topic of Saturday's Deseret News/Intermountain Healthcare Hotline. From 10 a.m. to noon, Dr. Kent Samuelson, chairman of the Division of Orthopedic Surgery, and Dr. Josh Hickman, orthopedic surgeon at the Joint Center, both at LDS Hospital, will take phoned-in questions. The number is 1-800-925-8177 and only works during hotline hours.

"For the hip, at least, occasionally injuries can be helped arthroscopically, with a scope," said Hickman. "But most people who have problems with the hip have arthritis, and the cartilage is worn, so they need hip replacement."

End-stage osteoarthritis is the leading reason for total joint replacement, Samuelson said. When cartilage is worn away to "bone on bone," nothing short of replacement provides significant relief.

In 2003, about 418,000 total knee replacements and more than 220,000 hip replacements were performed in the United States. As the population gets older, that number will just get higher. But artificial joints typically last longer now than in the past — about 20 years or more. And that eliminates some of the earlier bias against replacing painful joints in patients before they are 65 or older, the doctors said.

The issue is nearly always cartilage and how torn and worn it is. Sometimes, it's entirely worn away by past injuries, arthritis or other inflammatory joint problems, infections or anatomical anomalies. Hickman said with hips, the problem may involve how the pelvis is shaped. The angle of the cup plays a role in arthritis.

Common joint problems may be treated by a primary care doctor, a rheumatologist or an orthopedic surgeon.

There are nonsurgical options for damaged joints that can delay the need for surgery or fix the problem outright. When there are early signs of arthritis, injections and activity modification can both make a difference, Samuelson said. "If your tennis game is off and your knee hurts, you want to try the conservative things. Playing singles tennis with a total knee (replacement) is probably not a good idea."

A tear in the knee's meniscus, for instance, can be fixed. So can injured ligaments. There's even a partial knee replacement.