I work with osteoporosis patients regularly. Physicians send them to me to increase bone density. That should be the main goal.
To achieve this you need to know the severity of the osteoporosis. The client’s physician should be able to provide this information. Most physicians, however, don’t understand how exercise effects osteoporosis. Many think that mere walking will help. It won’t. The patient needs a heavy resistance exercise routine that puts heavy loads on the bones. These might include back squats for axial loading. This can help the vertebra. Leg press, lunges, box drops and box jumps. These affect the long bones of the legs and the flat bones of the pelvic region. Shoulder press and bench press affect the long bones of the arms.
Any core work will be helpful for core strength.
Remember progression and proper form are key. Work with you client to find the correct intensity, but overload is critical. It also takes many months to improve osteoporosis.