Dr. Lisa Pomranky
says

Osteoporosis is a disease where the bones are weakened and is silent symptomatically until a fracture occurs.  Women should be screened with a bone density test over the age of 65 and men over the age of 70.  Bone density exams are referred to as a DXA.  This stands for Dual-energy Xray Absorptiometry.  Your doctor may recommend this after a fracture depending on how you did it, as some fractures occur at increased frequency in people with osteoporosis.