Patellar instability is an umbrella term that overs several kneecap abnormalities including patellar subluxation and patellar dislocation. Normally, the patella rests in a groove at the lower end of the femur (thighbone) called the trochlear groove.The underside of the patella is shaped like a keel and engages with this groove to ensure vertical movement of the kneecap as the knee is flexed and extended. Patellar instability can result from malformations of the trochlear groove (e.g. excessive shallowness) or from weakness of the quadricep muscles or lateral ligaments that are also responsible for keeping the patella in place. The condition may be addressed by knee braces such as those below, that are designed with this in mind. Please check with us or consult with your doctor to ensure that brace you choose is suited for your particular condition.