By Tibial Tubercle Osteotomy (TTO) the insertion site of the ligamentum patella on the tibia is moved either inwards or down causing a more aligned traction of the patella.
If your Patella is placed to high in relation to the groove (Patella alta), the Tibia Tubercle Transposition can bring your Patella downwards into the groove. If the Tibial Tubercle is outward placed, your Patella tends to track outwards and by medialization (moving inwards), your patella will track more correctly. The surgery should only be performed if you are having either an increased TT-TG or an decreased cartilage overlap between the patella and the trochlea groove (less than 6 mm) - read more here. A little variation of this surgery is called Fulkerson osteotomy and this can be used for a special group of patients having anterior knee pain caused by osteoarthritis in the Patellofemoral joint.
As it appears from the picture at left, the Tibial Tubercle is chiseled off and moved inwards. The bone block is fixated again by 2 - 4 screws.
This demonstrate a Patella Alta - meaning a high riding kneecap
The distalisation of the tibial tubercle have brought the patella into the trochlear groove