Osteoporosis is the most common metabolic bone disease in the United States and is a chronic progressive disease that can affect almost the entire skeleton. It is characterized by low bone mass and bone weakening that increases the risk for bone fractures. Osteoporosis often does not become clinically evident until a complication occurs such as a bone fracture that can lead to severe pain, disability and a poor quality of life.

There are about 10 million people in the United States that have osteoporosis and 14 to 18 million that have osteopenia - low bone mass. Osteoporosis affects one in every three women and one in every eight men worldwide.

Osteoblasts are specialized cells that make bone and osteoclasts are unique cells that resorb bone. These cells are constantly remodeling the skeletal system with bone resorption followed by bone formation known as coupling. Osteoporosis occurs when there is a disruption in the coupling process that leads to a reduction in skeletal mass.

During the post menopausal state bone loss is due to excessive osteoclast activity whereas the loss of osteoblasts leads to skeletal mass loss in the elderly.

Osteoporosis can be divided into primary and secondary disorders. Primary osteoporosis can be categorized as juvenile, postmenopausal, and age related or senile. Juvenile osteoporosis occurs in children or young adults with an onset of 8 to 14 years of age. The characteristic finding in juvenile osteoporosis is the abrupt commencement of bone pain or a trauma related fracture. Post menopausal (type I) osteoporosis occurs in women from the age of 50 to 65 years old. This form of osteoporosis is exemplified by accelerated bone loss. The skeletal loss occurs primarily from trabecular bone leading to distal forearm and vertebral body fractures. Senile osteoporosis (type II) occurs in both men and women over the age of 70 years and is due to the loss of cortical as well as trabecular bone. Fractures of the wrist, spine and hip are often seen with type II osteoporosis.

Secondary causes of osteoporosis are due to disorders classified as genetic (congenital), endocrine, hypogonadal states, deficiency states, drug-induced, inflammatory states, hematologic, neoplastic and miscellaneous.

Risk factors for the development of osteoporosis include advanced age, alcohol use, androgen or estrogen deficiency, amenorrhea, body weight less than 127 pounds, Caucasian or Asian ethnicity, calcium deficiency, early menopause, family history of osteoporosis, female gender, fragility fracture, late menarche, physical inactivity and tobacco use.