[Imaging and preoperative planning for osteotomies around the knee]

Physiologic alignment of the human lower leg is well defined. The etiology for malalignment comprises constitutional, degenerative and posttraumatic conditions. Osteotomies around the knee can correct the malalignment, provided that the origin of deviation is in proximity of the knee center. Crucial factors for the evaluation of axis deviation are the weight-bearing line, the mechanical axes of femur and tibia, the joint line angles and the center of the hip, knee and upper ankle joint. Careful preoperative planning is mandatory for reproducible clinical results. For the treatment of varus osteoarthritis of the knee, a slight overcorrection to the 62% width of the lateral tibial plateau is frequently advocated. In valgus knees, a correction of the postoperative weight-bearing line to physiologic conditions (44% of the lateral tibial width) is regarded to be sufficient. Recently, individualized planning of the correction angle is advocated to better address the underlying pathology of each patient.