Introduction
Your knee consists of two halves each designed to carry more or less equal loads. In a perfectly aligned lower limb, a straight line running through the middle of the hip to the middle of the ankle will also cross the middle of the knee. This is called the weight-bearing line of the leg. If a person has knock knees the alignment is abnormal and the weight-bearing line will not run through the middle of the knee, but through the outer half, resulting in excessive load on this part of the knee (a so-called valgus knee). With time this will result in abnormal wear of this outer part of the joint. This can be compared to the wear of a car tyre when the alignment of the wheels is incorrect.
One of the solutions to this localized wear in the joint is to realign the lower leg, a procedure known as an osteotomy. The principal of the osteotomy is to realign the leg so that the weight-bearing line will run through the inner medial half of the knee.
The exact alignment of the lower limbs is measured on a special long X-ray where the hips, knees and ankles can be seen on one view. From these X-rays we can measure the degree of malalignment and plan how much we should realign the leg. The correction will be performed on the upper leg (femur) above the knee joint.
