How many surgical methods are there for knee osteoarthritis? What are the appropriate treatments for each method?

Author: Guo Xiaozhong, Chief Physician, First Affiliated Hospital of Tsinghua University

Reviewer: Li Jun, Chief Physician, Peking University First Hospital

If knee osteoarthritis continues to worsen with age or due to other factors and conservative treatment is ineffective, surgical treatment may be required, including osteotomy, unicompartmental knee replacement, and total knee replacement.

In the early stage of knee osteoarthritis, if there is obvious varus or valgus deformity of the knee joint, and the wear of the medial or lateral articular cartilage is not particularly severe, the deformity can be corrected and osteotomy can be performed. Correcting the varus or valgus deformity of the knee joint can restore the force line of the knee joint to normal, and the force distribution of the inside and outside can be even. The force-bearing area will increase, the local pressure will decrease, and the rate of local cartilage wear will slow down, thereby preventing the further aggravation of knee osteoarthritis.

When there is a varus deformity in the knee joint, osteotomy is usually performed on the tibia. There are two methods of tibial osteotomy: one is to perform a closed wedge osteotomy on the outside of the tibia, that is, the outside of the knee joint. After the operation, the two sections of the bone are in close contact, thereby effectively correcting the varus deformity; the other method is to perform an open wedge osteotomy on the inside. After the operation, the two sections of the bone are separated and fixed with a steel plate, which requires a higher fixation strength. For valgus deformity of the knee joint, correction is mostly performed on the femur, which is also divided into two methods: closed wedge and open wedge, and requires the use of a steel plate for fixation.

Unicompartmental knee replacement is relative to total knee replacement. The knee joint consists of the medial compartment, lateral compartment, and patellar compartment. When one of the three compartments is diseased, a partial knee replacement surgery, i.e. unicompartmental knee replacement, can be performed.

Figure 1 Original copyright image, no permission to reprint

Unicompartmental knee replacement is mainly suitable for cases where there is obvious wear of the cartilage on one side of the knee joint, such as exposed bone under the cartilage in the medial or lateral compartment, worn cartilage, and broken meniscus. At this time, a unicompartmental knee replacement is required to replace the cartilage on the bad side and restore its normal function.

Unicompartmental knee replacement actually removes the damaged cartilage of the tibia and part of the bone under the cartilage, removes part of the cartilage and bone under the cartilage of the femoral condyle, and then puts an artificial prosthesis on it, uses bone cement to make it integrated with its own joint, and adds a small gasket in the middle to act as a meniscus. The cartilage is removed and the unicompartmental prosthesis is used to replace the damaged cartilage and subchondral bone to restore the normal structural relationship. When moving, there will be no bone grinding against bone, and the symptoms will be greatly improved, and normal life and work can be resumed. Unicompartmental knee replacement can be used for more than 20 years. If problems occur again after 20 years, it can be changed to total knee replacement surgery.

In addition, if there are problems with both compartments, such as the medial and lateral compartments, or problems with the patellofemoral joint, the entire knee joint will have bone hyperplasia, cartilage wear, and exposed bones on both sides of the joint, which is a typical manifestation of severe osteoarthritis. Unicompartmental replacement can no longer solve the problem of the entire joint, and total knee replacement surgery is required.

Figure 2 Original copyright image, no permission to reprint

Total knee replacement is to remove the two worn joint surfaces, namely the worn joint surface of the femoral condyle and the worn joint surface of the tibia, including the thin layer of bone tissue under the joint surface; then the femoral prosthesis is wrapped on the femur, and the tibial prosthesis is inserted into the tibia side, with a polyethylene gasket in the middle, which acts as a buffer between the femoral prosthesis and the tibial prosthesis. The femoral prosthesis can move well on the gasket and even return to the normal range of motion. When walking with weight, the bones no longer grind against each other, which can eliminate pain symptoms and improve the range of motion of the knee joint.

After total knee replacement, most patients with knee osteoarthritis can recover well and even achieve normal joint mobility. If the replacement is not effective, rehabilitation therapy can help improve function and relieve symptoms. You can also continue to take some medication to relieve symptoms. At the same time, do rehabilitation training to promote a positive development.

Theoretically, a total knee replacement can be used for more than 20 years. If the artificial joint is damaged, a knee revision surgery can be performed if the physical condition allows.