If a joint damaged by osteoarthrosis can be made to heal reliably, this would be an ideal treatment. Preserving living tissues makes better sense than replacement, since replacement means discarding the anatomic joint forever. Osteoarthrosis is a disruption of the normal balance between mechanical stresses and the resistance of the tissues of the joint to articular pressure. For a surgical approach to be reliably effective, the procedure must be planned graphically and performed accurately. Articular pressure can be reduced by diminishing the force transmitted across the joint and by enlarging the force-transmitting surface of the joint. An inverted dome-shaped density beneath the lateral plateau indicates exaggerated pressure there, with valpus deformity of the knee. This valgus deformity must be very slightly overcorrected. An osteotomy is performed just proximal to the femoral condyles.