Advanced poses such as Sirsasana (headstand) or Sarvangasana (shoulder stand) might literally be bone crushing for individuals with low bone density. If you have low bone density or osteoporosis, you must avoid poses that have forward flexion – or rounding of the spine. Instead, try doing Cobra poses that are considered extension poses to help you stretch and build strength without too much pressure exerted on your bones.
Balance is very important, as is proper alignment. So go slow and work up because, for beginners, balance poses can lead to falls if you are not ready. Falls for people with low bone density or osteoporosis can lead to fractures! During my last yoga class, someone lost their balance and almost started a whole domino effect! Bad falls like these can throw off the vibe of the yoga session and impact others around you, not to mention potentially be dangerous! Start your balance poses with support, such as a block, and pay attention to proper alignment to work towards better balance.
The message you should take is to treat your yoga experience as a gradual process that need not be rushed. Pay attention to not only your mental ability and focus, but your physical abilities. Slow down and go easy. Your ultimate goal for your bones is to create a strong foundation, however, slow the process may take.