Dear Dr. Roach: I am a healthy 79-year-old female who recently underwent a right total knee arthroplasty. In a routine post-operative X-ray there was indication of early osteopenia in my long bones. I live in Montana and walk regularly during the summer months, but during winter it is more difficult. I have an exercise bike and can change the resistance level when biking. Is this the same as “weight bearing” exercise? Should I consider getting a treadmill or some other type of indoor exercise equipment? I live in a rural area and prefer to exercise at home but have little extra space for a lot of equipment. — K.L.

Answer: Before I even consider it, I’d want to know if you have had a bone density test, often called a DEXA. Plane X-rays are not reliable indicators of osteopenia or osteoporosis. That information is critical to consider whether lifestyle changes like diet, exercise and supplemental vitamin D are likely to be effective or whether you would greatly benefit from prescription medication. Vitamin D levels in a person living in Montana in the winter are very likely to be low unless they are taking supplemental vitamin D. The low energy of winter sunlight in the North makes supplementation a wise choice if you aren’t already doing so.

The best type of exercise is a matter of debate, but a review looking at multiple studies found that for people with osteoporosis in the long bones (like your femur, the thigh bone that can break in a hip fracture), strength training is highly effective. You can do strength training by raising the resistance on your exercise bike.

You don’t need specialized equipment to do weight-bearing exercise. Jumping rope, callisthenic-type exercises and dancing are all choices that require little more than floor space.