Revision total knee arthroplasty (TKA) is often accompanied by severe bone loss, due to infection, osteolysis, loosening of the primary implant or iatrogenic bone loss owing to implant removal.

As the number of revision knee arthroplasty is estimated to increase by 600% until 2030, it is important to further improve surgical solutions.

Proper fixation and by that good long-term survival depends on the amount and type of bone loss and on the amount of bone that is left for fixation.

Therefore, the following 2 classifications are important, and each case should be analysed by applying both pre-OP and intra-OP.

Classification of bone stOptimal surgical strategy depends on the size and shape of the bone stock defect, which is described by the classification of the Anderson Orthopedic Research Institute (AORI).

More specifically, an AORI defect grade I describes an isolated cystic lesion near the joint line, demonstrating intact metaphysis and cortical bone.

An AORI defect type IIa shows half sided (medial or lateral) bony lesion of the metaphysis, while type grade IIb shows bilateral defect of femoral or tibial metaphysis.

An AORI defect type III shows complete loss of metaphysis including insufficiency or tear of collateral or patella ligament (Fig.