Osteoporosis is a systemic skeletal disease characterised by low bone density and micro architectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. It is a silent disease. It is the result of the negative balance between bone formation and bone resorption, i.e. more bone is lost than is formed. It is the most common bone disease worldwide and is now a major health problem. Bones require a normal level of systemic hormones, adequate caloric intake, particularly protein, calcium and vitamin D and regular weight-bearing exercise throughout life. A large bone mass early in life protects against osteoporosis. Peak bone mass is determined by sex, heredity family history, race, diet and exercise. Sixty per cent of bone growth occurs during adolescence. Moderate exercise protects against osteoporosis, but too little or excessive exercise may cause osteoporosis.