My mother is 90 years old, weak bones, weak muscles. what is a great supplement?

Calcium and vit D: Adults with thin bones, called osteopenia, benefit from taking about 1200-1500 mg of calcium daily, along with about 800 units of vitamin d. Osteoporosis is a more severe form of thin bones that may require a medication to help prevent broken bones. 800 units/day of vit d also can help prevent falls in older persons. A good iphone reference for general screening is my health checklist 2012.