Rib fractures occur when one or more of the bones that make up the rib cage is broken, usually due to a direct traumatic impact or an indirect crushing injury. Other causes of rib fractures include sustained and forceful coughing, diseases such as cancer, and certain infections. Compromised bone structure—such as that occurring as a result of osteoporosis or metastatic deposits—increases the risk of fractures. The middle ribs are the most vulnerable to such breaks, with the seventh and tenth ribs being the most common sites of rib fractures. This injury tends to be incredibly painful because the ribs move with breathing. Possible complications of rib fractures include torn or punctured aorta (usually resulting from a complete break in one of the first three ribs), punctured lung (usually resulting from a break in one of the middle ribs), and lacerated spleen, liver, or kidneys (usually resulting from a break in one of the bottom two ribs). While there is no specific treatment for rib fractures, there are some measures that can be taken to lessen the impact of the symptoms, including administration of pain relief medications and injections of anesthesia around the nerves near the ribs. Most ribs heal on their own after about six weeks.