Broken wrist. Coloured X-ray of a Colles' fracture of the wrist, an injury usually caused by the extension of a hand to lessen the impact of a fall. In a Colles' fracture, the radius (the bone on the thumb side of the lower arm) breaks near the wrist, and the wrist and hand (upper left) are displaced backwards. This type of fracture is more common in the elderly, whose bones have been weakened by osteoporosis. Treatment of the fracture is with surgical repositioning of the bones followed by immobilisation in a cast for up to two months. The injury slightly increases the risk of developing arthritis in the joint.