Stiffness and pain in the legs or knees are most commonly associated with osteoarthritis and are rarely caused by osteoporosis. Back pain, however, may be due to osteoporosis or other conditions such as osteoarthritis or degenerative disc disease. It is possible to have osteoporosis and osteoarthritis as well as other conditions at the same time. Hence, you should visit our doctors to seek professional medical help and diagnose the disease at the earliest.