This operation is performed to improve stability of the knee cap (patella) reducing the sensation of dislocation or giving way of the knee. It is also sometimes used for treating various forms of anterior knee pain (patello-femoral pain) syndrome. It involves releasing the tight tissue on the outer side of the patella (lateral release) and moving the bony attachment point of the tendon controlling the knee cap (patella tendon) into a better position.
The effect of this is to hold the patella within its normal grove or track on the thigh bone, reducing the tendency for it to slide out of position to the outer side (lateral side). The tendon attaches to the tibial tubercle, which is the bony prominence below the patella, and the operation moves this forwards (anteriorly) and to the inner side (medially). It is then held in place with two screws, which usually do not have to be removed.