A rib fracture is a break or fracture in one or more of the bones making up the rib cage. The first rib is rarely fractured because of its protected position behind the clavicle (collarbone). However, if it is broken, serious damage can occur to the brachial plexus of nerves and the subclavian vessels. Fractures of the first and second ribs may be more likely to be associated with head and facial injuries than other rib fractures. The middle ribs are the ones most commonly fractured. Fractures usually occur from direct blows or from indirect crushing injuries. The weakest part of a rib is just anterior to its angle, but a fracture can occur anywhere. The most commonly fractured ribs are the 7th and 10th. A lower rib fracture has the complication of potentially injuring the diaphragm, which could result in a diaphragmatic hernia. Rib fractures are usually quite painful because the ribs have to move to allow for breathing. When several ribs are broken in several places a flail chest results, and the detached bone sections will move separately from the rest of the chest.