Osteoporosis is a condition characterized by a decrease in the density of bone, decreasing its strength and resulting in fragile bones. Osteoporosis literally leads to abnormally porous bone that is compressible, like a sponge. This disorder of the skeleton weakens the bone and results in frequent fractures (breaks) in the bones.

Normal bone is composed of protein, collagen, and calcium all of which give bone its strength. Bones that are affected by osteoporosis can break (fracture) with relatively minor injury that normally would not cause a bone to fracture. The fracture can be either in the form of cracking (as in a hip fracture) or collapsing (as in a compression fracture of the vertebrae of the spine). The spine, hips, ribs, and wrists are common areas of bone fractures from osteoporosis although osteoporosis-related fractures can occur in almost any skeletal bone.

Osteoporosis can be present without any symptoms for decades because osteoporosis doesn't cause symptoms until bone fractures. Moreover, some osteoporotic fractures may escape detection for years when they do not cause symptoms. Therefore, patients may not be aware of their osteoporosis until they suffer a painful fracture. The symptom associated with osteoporotic fractures usually is pain; the location of the pain depends on the location of the fracture.

Fractures of the spine (vertebra) can cause severe "band-like" pain that radiates from the back to the sides of the body. Over the years, repeated spinal fractures can lead to chronic lower back pain as well as loss of height or curving of the spine due to collapse of the vertebrae.