Hi Frank ... thanks for raising this topic again.
As always, anyone with osteoporosis to any degree should check with their health care provider before beginning any yoga practice. It would also be a very good idea to know their Dexa score so they can tell their yoga teacher as well (a Dexa scan reveals the degree of degeneration in the lumbar spine, which is a good indicator of overall bone density.)
I have mentioned in the past, Dr Loren Fishman's upcoming book Yoga and Osteoporosis and his web site,
http://www.sciatica.org. In his web site you will see that he has 12 recommended (yang) poses for people who want to i) avoid getting osteoporosis, ii) already have osteoporosis and iii) for folks who have the milder form, osteopenia. In the 12 postures, he does include twists and very mild forward folds (like down dog, of course modified greatly.)
As you said, never say never! It all depends on the person, the severity of the condition and what their health care provider says. But, to strengthen the bones, we do need to stress them. We just have to find out the appropriate way to do that. In Dr. Fishman's 12 posture sequence, he is using the muscle to apply the tension, which is perfectly okay since the poses are being held for a very short time. I believe (but have not seen any studies to verify this belief) that as the condition improves, or for people who have low Dexa scores, Yin Yoga can be equally or more effective at stressing the bones.
The most common sites for osteoporosis are the wrists (~10% of the time), the hips (~20%) and the lower back/lumbar (~50% of the time.) Standing poses are great for the legs, but that is not where most people have the problem. The standing poses in Dr Fishman's series also works the hips, which is great. But the spine may best be worked in a yin manner, like Sphinx pose, or a supported Caterpillar (try resting your arms/head on a chair), or - yes - even Child's Pose, which is a very gentle forward fold.
However, Caterpillar and Child's Pose are forward folds! The student's health care provider may suggest, to avoid any possibility of a "wedge fracture" of the vertebrae, that all forward bends should be eliminated for now. This would then includes Yin Yoga forward bends. A wedge fracture is where the vertebra gets thinner in the front of the spine, until eventually it fails and fractures. Since this is the front of the spine, forward bends put extra pressure onto the degenerating bone.
Default to very mild forms of the postures and make sure that these are not making matters worse. Then slowly start to increase the time in the poses and the intensity of the position. Go slow, but do try. Again, everything needs stress to stay healthy.
Cheers
Bernie
