Hello @cpb Collagen is a protein component of all connective tissues in the body including bone and skin. When bone is formed or healing as in the case of a fracture, a collagen fibrous network is laid down first and then populated with the cells that create bone. If you eat meat in your diet, you are eating collagen. Bone has to have a tensile strength so it has a bit of flex for shock absorption which it gets from collagen. It sounds like your friend had some good advice from her physician.