Insufficiency fracture is a small subset of a larger group of fractures called stress fractures. Insufficiency fractures are caused by the effect of normal stress on weakened bone. Osteoporosis is the most common cause of bone loss leading to insufficiency fractures.

Loss of bone density from osteoporosis decreases the bone's ability to "give" slightly and resist everyday loads. The loss of this "elasticity" seems to affect the spine, tibia and fibular (lower leg bones) and calcaneus (heel) most often.

These fractures seem to be on the rise in older adults, especially postmenopausal women.