Dear Doctor: I recently added running to my weight-loss program. Not only do I feel better, but the pounds are also coming off faster. However, I keep reading that running is bad for my knees, so it makes me wonder -- am I making a mistake?

Dear Reader: We're happy to reassure you that running, when done properly, is not bad for your knees. In fact, a number of recent studies suggest the opposite is true.

In addition to a lowered risk of stroke and heart attack, runners in the studies had lower rates of osteoarthritis than the non-runners did. And thanks to the runners' general level of fitness, their chosen form of exercise was seen as beneficial to maintain joint health.

The idea that running is bad for your knees is one of those myths that just won't go away. It sounds like common sense -- you hit the ground with a certain amount of force as you run, so over the course of a few miles (or quite a few, if you're a distance runner) your knees must take a beating. But numerous studies conducted over the last decade have repeatedly shown that's not so.

Researchers found no correlation between running and osteoarthritis, also known as OA. Sure, a percentage of the participants in the long-term studies did develop OA. However, when scientists looked closely, it turned out that running was not a risk factor. Instead, obesity, family history, advanced age and previous muscle or joint injury proved to be the real predictors of future osteoarthritis.

In fact, it turns out that people who exercise -- and this includes short- and long-distance runners -- get extra protection against OA. As we mentioned earlier, runners' muscles are more toned and therefore reduce the pressure the joints are asked to bear. Add in the fact that runners tend to have a lower BMI -- that's body mass index, a measure of fitness calculated by height and weight -- and researchers agree that running is good for you.

Before you race out the door, though, there are caveats. If you have injured yourself in the past, whether a muscle, cartilage or ligament, you may indeed be at risk of further damage. But if you're a healthy individual without a history of injury, running is a good way to boost your weight loss -- and, as you also noticed, your mood.

A few things to consider as you add regular running to your routine:

-- If you're over 40 years old or more than 20 pounds overweight, it's probably wise to talk to your primary care physician about your plan to run regularly.

-- Proper training takes time, probably longer than you imagine. Don't think in terms of miles at the beginning. Instead, pick a time interval -- 10 or 20 minutes to start -- and mix running with walking as you ease into your new routine.

-- Get good shoes and insoles. It makes all the difference to the alignment of your leg, which helps protect your knees. And be sure to replace your running shoes before they wear out.

-- Never run when injured. Ever. Sharp pains, sudden pains or pains that are on one side of the body but not the other can be warning signals.

-- Yes, you really do need that day (or two) of rest per week to stay injury-free.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)

Dear Doctor: I read that dementia rates are going down due to rising education levels, but I don't have a college degree. Should I be more worried than most?

Dear Reader: Dementia is a scary disease, causing not only loss of memory but also the inability to reason through problems and, for many, difficulty with even the daily tasks of living. One bright spot is that dementia rates are indeed declining. This was first noted in the United Kingdom in 2013, where researchers in the medical journal Lancet reported a 24 percent decline in dementia rates compared to 20 years previous. The question is: Why the decrease?

A recent study published in the Journal of the American Medical Association attempts to answer that question, assessing differences in dementia rates in the United States between the years of 2000 and 2012. The data were taken from the Health and Retirement Study, which is based on a questionnaire given to thousands of people over the age of 50. The study looked at 10,000 people in 2000 and another 10,000 people in 2012. In this study, researchers found a 24 percent decrease in the dementia rate between 2000 and 2012, and one difference noted by the authors of the study was that overall respondents in 2012 had one more year of education than those in 2000.

A logical question is whether the population in 2012 was simply healthier. That does not appear to be the case. In fact, the 2012 population generally had greater rates of high blood pressure and diabetes, both of which are risk factors for dementia. To that point, it's possible that the more modern and stricter treatments for diabetes and high blood pressure played a role. After all, statins, as well as medications for high blood pressure and diabetes, can reduce the effects of diabetes and high blood pressure on brain function.

But ultimately the authors concluded that the higher level of education was the primary contributor to the decline of both dementia and cognitive impairment. That benefit may come from the creation of greater amounts of brain reserve, so that when brain function decreases years in the future, the effect may not be as obvious.

My belief is that any form of education is important. Although the study above showed that an additional one year of education had benefit, there are other ways of getting an education, such as learning a language. Numerous studies have shown that people who are proficient in two languages have a significant decline in dementia. So if you have the time, learning another language would be a worthy investment.

Please note, however, that I have had patients with high education levels get dementia, so education is not a total preventive.

But I would encourage you to continue to use your mind -- challenging yourself with learning new material and continuing to educate yourself. You don't need to sit in a class for this. A lifelong process of learning and understanding may itself decrease your chances of dementia.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)

Dear Doctor: I just turned 65, and even though I'm strong and healthy, my friends say I should be concerned about osteoporosis. What is it, and how do I know if I have it?

Dear Reader: Osteoporosis, which literally means "porous bones," is a progressive disease in which bone mass is lost. As a result, bones become thinner, more fragile and are at higher risk of fracture. People with osteoporosis most often break a bone in the hip, forearm or spine.

Although osteoporosis can occur in men and women of any age, post-menopausal women have the highest risk. This is due to the steep drop in the production of estrogen, a hormone produced by the ovaries, which protects against bone loss.

Risk of osteoporosis increases along with a person's age. A family history of the disease is an indicator of risk, as are alcoholism, cigarette smoking, anorexia and steroid therapy. Race also plays a role, with Caucasian and Asian women more likely to develop osteoporosis than other ethnicities.

To understand osteoporosis, let's first talk about bones:

Your skeleton, which supports and protects your body, is made up of living tissue. It's also a storehouse of essential minerals that are held within your bones. Throughout your life your bones go through a metabolic process called remodeling, in which old bone tissue is removed from the skeleton and new bone tissue is formed.

As we age, the formation of new bone tissue slows. In people with osteoporosis, the formation of new bone can't keep pace with the removal of old bone, which results in a net decrease in bone density. In addition to an increased risk of fracture, people with osteoporosis experience a loss of height, stooped posture and decreased mobility.

So how can you know if you have osteoporosis?

Since in its early stages osteoporosis typically does not have symptoms, a bone density test is needed for an accurate diagnosis. This is a painless scan in which low-level X-rays are used to reveal the proportion of minerals in your bones. During the test you lie on a padded table as the technician scans several areas, usually your hip, spinal column and wrist.

Treatment for osteoporosis ranges from lifestyle changes, such as adding an exercise plan and switching to a diet rich in calcium and vitamin D, to a range of medications that you would discuss with your doctor.

No matter your age, there are things you can do to keep your bones strong. Calcium is one of the building blocks of new bone, and to successfully absorb that calcium, your body needs vitamin D. Dairy foods, certain nuts and green leafy vegetables contain lots of calcium. Eggs, fatty fish and fortified milk contain vitamin D. Talk to your doctor about whether you need supplements of calcium and/or vitamin D.

Staying physically active strengthens both muscle and bone. Try weight-bearing exercises three to four times per week, and don't forget about balance and agility exercises, which can help prevent a fall.

Your bones hold you up, allow you to move and contain the marrow that produces about 230 billion red blood cells per day. We think your friends have a point here -- don't take your bones for granted.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095.)