Osteoporosis is a disease where bone mineral density is reduced, making bones more fragile and compressible. It most commonly affects women after menopause. While osteoporosis often has no symptoms until fractures occur, common risk factors include being female, having a small frame, family history, smoking, poor nutrition and vitamin D deficiency. Diagnosis involves bone density tests and x-rays, with treatment focusing on bisphosphonates, hormone replacement, calcium and vitamin D supplements.