you know yourself better than anyone else. you know if you are likely to fall playing tennis or golf or any of the other sports that are not specifically forbidden for people with osteoporosis (like sky diving bungee jumping or ski jumping)! if you have played tennis for many years and have been safe then you may well be fine with continuing it. it is all a matter of risk. the problem with tennis is that you can fall slide and get hit really hard by a ball. maybe doubles is a better approach where your area of responsibility is smaller. on the other hand if you prefer to walk and work with weights that is great too! it is important to enjoy your exercise but to also be sure that it is safe.
are some kinds of exercise dangerous when you have osteoporosis?