Fractures of the patella are not of frequent occurrence; they constitute about 2 per cent, of all fractures, and are found more frequently in the male than in the female—in the proportion of about five to one. Fractures of this bone demand careful consideration, on account of its close proximity to the knee-joint, and also in consequence of the imperfect way in which the fragments unite; fracture of the patella is caused by muscular action or direct violence. The direction of the fracture may be transverse, vertical, oblique or even stellate. In the fracture produced by sudden and violent muscular contraction, the transverse variety usually occurs; when the fracture is caused by direct violence, the direction may be vertical, transverse, oblique or stellate, or the fracture may be comminuted. In fracture of the patella the kneejoint is always opened, unless the extreme lower end of the patella is broken, in