Malalignment of the knee joint causes arthritis in later life. Currently there are three surgical ways to treat knee arthritis: total knee replacement, partial knee replacement, and high tibial osteotomy (HTO). The former two very much focus on treating the effect of malalignment, i.e. removing the arthritic joint. However, HTO addresses the cause of the arthritis, namely the joint malalignment. This preserves the patient's joint and it means that a patient will start using the unaffected part of the knee joint more.