The mechanical alignment of the lower extremity is an important consideration in the long-term outcome following total knee arthroplasty (TKA) or high tibial osteotomy (HTO) . Alignment between the hip and the ankle through the knee joint has been used in determining coronal alignment, based on the assumption that weight-bearing forces pass through the centre of the knee joint during neutral mechanical. However, the weight-bearing vector can be affected by hindfoot and midfoot alignment because load is transmitted not from the ankle joint, but from the ground reaction point. Thus hindfoot alignment after knee correction may critically affect the longevity of the prosthesis~Most patients with some degree of knee joint deformity, which in turn may be associated with a deformity of the foot. In fact, an association between varus alignment of the knee joint and valgus alignment of the foot in osteoarthritis patients has been reported. Because the subtalar joint compensates for the knee joint deformity , correction of the deformity after TKA or HTO can affect foot alignment. Improvements in midfoot and hindfoot alignment have been noted in patients with osteoarthritis after correction of deformity. However, foot valgus may also persist, with little improvement after knee correction.
This study evaluated the change in foot alignment after TKA or HTO by prospectively analyzing the correlation between the knee joint and the foot deformity, the post-operative improvement in the foot deformity, and the long-term post-operative changes in foot alignment.