ABSTRACT

Many children demonstrate a varying degree of underlying ligamentous laxity, upon which is superimposed an initial trauma that is often due to an athletic event. Habitual, or obligatory, dislocation of the patella is a patellar dislocation that occurs every time the knee is flexed and due primarily to a shortened but otherwise normally positioned quadriceps mechanism. It is important to be clear about what recurrent, habitual and persistent dislocations of the patella are to avoid any confusion in the terminology. This differentiation is also necessary because treatment approaches are quite different for congenital, habitual and recurrent dislocation. In the normal individual, the patella has an inherent tendency to move laterally on account of the alignment of the quadriceps muscle and patellar tendon; the angle between the long axis of the muscle and the patella tendon creates a vector that pulls the patella laterally.