Fracture of patella is usually caused by a sudden fall in which the patella is pulled by contracture of quadriceps muscle of thigh or bumps against the ground. Fracture caused by contracture of muscle is often transverse, with fragments separated from each other (see Fig. 18). Fracture caused by direct force is often comminuted, but with no marked displacement because of restraint of aponeurosis. This fracture often occurs in young and the middle aged people.