High tibial osteotomy (HTO) is a common and widely accepted procedure in orthopaedic surgery. In the literature, we find descriptions of the technique dating back to the 50s, with Jackson (Jackson, 1958). However, it was not until the 70s, with the publications of Conventry (Coventry, 1969 and 1973) and Insall (Insall, 1975), that proximal tibial osteotomy became common practice as a treatment option for medial compartment osteoarthritis of the knee usually associated to varus deformity. At that time, closing wedge osteotomies were performed, despite the greater technical difficulty and risks involved, as there were no fixation materials available that could enable opening wedge osteotomy. Only after the development of medial wedge plate fixation that opening wedge osteotomy became applicable (Puddu, 2004). The goals of HTO are: 1. To reduce knee pain by transferring weight-bearing loads to the relatively unaffected compartment; 2. To increase the life span of the knee joint, by slowing or stopping the destruction of the medial joint compartment. This could delay the need of a joint replacement.