This paper proposes a method of bone structure analysis that could be used to determine if a person has osteoporosis by analysing the cortical bone on medical images. Osteoporosis is a bone disease that leads to an increased risk of fracture. This method automatically extracts the cortical bone form medical images and measures its thickness. The proposed method was tested on medical images of healthy people and people with osteoporosis, to see if it could extract the cortical bone from both patient groups and to analyse the cortical bone thickness measurements.