What is knee malalignment?
In a normal leg, an imaginary straight line drawn from the center of the hip to the center of the ankle will pass through the center of the knee. This straight line, called the mechanical axis, illustrates the way our bodies bear weight when standing. Even a tiny variance of a few millimeters can make a huge difference in the wear-and-tear on a knee joint. Malalignment of the bones that form the knee joint may be present at birth or may develop following trauma or arthritis.
What are the types of malalignment?
- Genu varum:
- Tibia turns inwards in relation to the femur causing a bow-legged deformity
- Tend to have more wear on the inside (medial side) of their knees
- High tibial osteotomy (HTO) is more often recommended in these cases
- Genu valgus:
- Tibia turns outwards in relation to the femur causing a knock-knee deformity
- Tend to have more cartilage wear in the outside (lateral side) of their knees
- Distal femoral osteotomy (DFO) is more often recommended in these cases
How are varus and valgus deformities treated?
Knee osteotomy is the cutting of bone to correct the knee’s alignment and improve its function with the goal of reducing the development of osteoarthritis. The primary objective of the surgery is to shift weight away from the painful, damaged side of the knee joint and onto the healthy side of the knee joint. This is made possible by strategically repositioning the bones and then securing them in proper alignment.
- High Tibial Osteotomy (HTO) – most commonly performed to correct genu varum (bow-legged deformity). A wedge of bone is added or removed to an area of the tibia just below the knee
- Distal Femoral Osteotomy (DFO) – most commonly performed to correct genu varum (knock-knee deformity). A wedge of bone is added or removed to the femur, just above the knee. Less common than tibial osteotomies
- Closed osteotomy – A wedge of bone is cut and removed. The resulting gap in the bone is closed by bringing the two sides together and securing them with a plate and screws.
- Open osteotomy – A cut is made about three-quarters of the way across the bone. A wedge-shaped bone graft is inserted into the cut. The wedge is secured to the bone with a plate and screws. There are three types of bone graft: autograft, allograft, and artificial graft.