Hi Lynne,
Thank you for your question and your comment. Coming from a former dancer it is a big compliment.
It is safe. However, because of the wedging of your thoracic vertebrae I would strongly encourage you to incorporate the following two tips: 1. Be sure that when you’re sitting on the ball that your ball is large enough that it brings your hips 1/2 – 1 inch higher than your knees. An easy way to check this is to sit on your ball with a mirror at your side. You should see a slight downward slope from your hips to your knees. This will ensure that your lumbar spine is a little more extended to support the alignment of your thoracic spine.
2. As a dancer #2 will be easy for you. Sit the same way your would stand as a dancer. Keep the crown of your head to the sky and your spine long.
As for the osteoarthritis of your spine and hips it should be very good. I would invite you to also do the Beginner Level Balance exercises on the ball. The hip shift and circles are a great way to mobilize the joints of your hips and lumbar spine.
Be sure to build the strength in your back muscles and be diligent about how you move with your daily activities. You cannot reverse the wedging but you can stop the wedging from getting worse.
All the best,
Margaret

Hi Lynn,
You would replace the bouncing with marching from the ankle joint instead (the feet never leave the floor). Also, since I do not know how stable you are on the ball I recommend that you place cushions on either side and behind the ball as I demonstrate under the Exercise Safety Tips in my book Exercise for Better Bones. Better safe than sorry.
Margaret

Hi Anna,
Great question! Depending on how strong your pelvic floor is it may or may not be appropriate for you. As with all exercises, I emphasize in my book that individuals should adopt a pattern of breathing that is supportive of their pelvic floor. For those with exercise incontinence I recommend that they break down the warm up and see if they are able to do each sequence without leaking. If the bounce is too much force on their pelvic floor the same arm routine can be done without the bounce. You would replace the bouncing with marching from the ankle joint instead (the feet never leave the floor). Thank you for speaking up on behalf of all our pelvic floors!
Margaret

Suzanne