I had been swimming 3 times a week for two years when I received a diagnosis of early-stage osteoporosis. The only significant change to my daily routine in the next two years was using my rebounder for 20 minutes 3 or 4 times a week. After two years I was retested: the osteoporosis was gone.
Caution: My rheumatologist was very opposed to this form of exercise. She was afraid of the harm that could be done if I fell off the rebounder. I decided to do it anyway, but I am very careful; if I feel at all tired or dizzy I skip the exercises. I enjoy being able to jump and dance without hurting my knees. It's fun.
Where I live they sell rebounders at Sears and K-Mart. An inexpensive rebounder lasts me about 5 years before showing signs of wear, but I only weigh 112 pounds. For serious jumping, a large person might need to purchase a sturdier version.