A pathologic fracture is a broken bone caused by disease, often by the spread of cancer to the bone. Only a small number of conditions are commonly responsible for pathological fractures, including osteoporosis, osteomalacia, paget's disease, osteitis, osteogenesis imperfecta, benign bone tumours and cysts, secondary malignant bone tumours and primary malignant bone tumours.

Fragility fracture is a type of pathologic fracture that occurs as a result of a fall from standing height or less. There are three fracture sites said to be typical of fragility fractures: vertebral fractures, fractures of the neck of the femur and Colles fracture of the wrist. This definition arises because a normal human being ought to be able to fall from standing height without breaking any bones, and a fracture therefore suggests weakness of the skeleton.

As long as other pathologies are excluded (for example, cancer), then a pathologic fracture is diagnostic of osteoporosis irrespective of bone mineral density.