I have osteoporosis also. Luckily the only bone I have broken has been a minimally displaced rib fracture after a mountain-biking mishap. I have landed on my hips a LOT , and have come away with colorful bruises and hematomas. I definitely think about the fracture risks.

I am wearing some hip pads most of the time when mountain biking now. I got some liner shorts that have some 3/8 inch closed cell foam in them. The original shorts were by Six-Six-One, but the shorts did not fit right. So I took the foam pads out and sewed some fleece pockets on the inside of one of my older pairs of shorts and have been using the foam pads in them. They work pretty well and have cushioned a few direct hits. What I really need, though is some kind of flexible, breathable foam that I could dip my entire body into before heading out on the trails! As my BF says, I am one "technicolor Bay-Bee"

In addition to Fosamax and calcium (1200mg a day), I also try to get at least 1000 units of vitamin D daily. Research is showing that vitamin D may be more important than previously thought for preventing bone loss. I need to do more weight-bearing exercise, also. And of course, improve my riding skills so I spend less time on the ground!