Patellar subluxation or dislocation may be a one-time incident or recurrent in nature.
The instability may be related to a number of conditions that include knock-kneed posture, weark quadriceps, ligament laxity, flat-tened arches, or patellar misalignment, where the patella is located outward of the midline of the knee.
Patellar subluxation related to sports usually occurs when the foot is planted and a sharp inside move is made.