b. Severe Deformity. A hip injury results in severe deformity of the affected leg
and hip. There are two general categories of hip dislocations--anterior and posterior.
(1) Posterior dislocations comprise 70 to 80 percent of all hip dislocations.
A large force is required to strike the flexed knee with the hip flexed, adducted, and
internally rotated in order to cause a posterior dislocation. This injury occurs more
commonly during contact sports such as American football and rugby when a running
player is tackled and falls out of control onto a flexed knee. (See figure 4-2) The leading
cause of posterior dislocations is automobile accidents.
Figure 4-2. Posterior dislocation of the hip.