Osteoarthritis of the knee often affects only one side of the joint, resulting in the commonly seen “bow-legged” or “knock-knee” deformities. When this does occur, realigning the angle around the knee can shift your body weight so that the healthy side of the knee joint takes more of the stress. This reduces pain and delays the need for joint replacement surgery. This procedure is called an osteotomy.
The knee joint is formed by three bones. The femur (thigh bone) meets the tibia (shin bone) to form the main weight bearing part of the knee. The patella (kneecap) is located at the front of the knee and acts as a fulcrum to give the thigh muscles a mechanical advantage in straightening the knee. These three bones are covered by cartilage, a white highly polished surface that allows frictionless motion of each bone against another. Cartilage coats the end of the femur, the top part of the tibia and behind the patella. Osteoarthritis (OA) occurs when this surface cartilage wears out. [Figure 1]
Figure 1. Diagram on normal knee and OA
The knee joint is divided into three “compartments”. The weight-bearing compartment of the knee is called the tibio-femoral compartment, and this is subdivided into the (i) medial and (ii) lateral tibio-femoral compartments. The medial tibio-femoral compartment is on the inner part of the knee and the lateral tibio-femoral compartment is on the outer part of the knee. These two compartments carry the majority of the body weight during walking and running. The patello-femoral compartment is the space at the front of the knee between the patella and the femur. This compartment is loaded when performing activities that involve a lot of knee bending, eg walking up and down stairs, squatting or getting out of a chair.
Osteoarthritis of the knee commonly affects one compartment of the knee joint more than the other. While either tibiofemoral compartment can develop arthritis, it most commonly affects the medial compartment. As the cartilage wears away on the medial part of the knee, the space between the bones initially occupied by the cartilage starts to narrow. As this happens, a “bow-leg” deformity (varus deformity) may develop. Likewise if cartilage is lost from the lateral compartment of the knee, a “knock-knee” deformity (valgus deformity) develops. [Figure 2]
The rationale of osteotomy surgery is that the tibial or femoral bone is realigned via surgical correction (“controlled breakage”) so that the patient’s body weight is shifted from the arthritic compartment across to the more healthy cartilage of the non-affected compartment. The osteotomy is then held in place with a strong surgical plate and screws until the bone heals in this new position. [Figure 3]
The greatest advantage of an osteotomy is in preserving one’s own knee joint as opposed to replacing the knee joint with a prosthetic device (knee replacement or arthroplasty).
Figure 2. Alignment diagram of the knee
Osteotomy surgery is generally reserved for younger, active patients who have osteoarthritis affecting only one compartment of the knee joint. It has been shown to have good effect in increasing the life span of the natural knee joint and delaying the time before knee replacement surgery becomes necessary.
Figure 3. Opening wedge osteotomy of femur and tibia with plate and screw fixation
Most patients who require an osteotomy have underlying arthritic pain (typically a dull ache) localised to the affected compartment of the knee joint. The aim is to decrease the pain on the affected side of the knee by shifting body weight to the normal side of the knee and thereby delaying the need for a joint replacement. It often allows patients to perform high impact activities (e.g. running and impact sports), which are not recommended with joint replacement surgery. In order to be a candidate for this operation, your surgeon will ensure several criterion are met. This includes having functioning ligaments around the knee, an adequate range of motion of the knee joint, and minimal arthritis in other parts of the knee.
Prior to undergoing any surgery, you will have imaging of your knee to assess the degree of arthritis. This will include x-rays which will show narrowing of the affected compartment of the knee, as well as specialised x-rays (4-foot x-rays) which take a picture from the hip joint all the way down to the ankle joint (i.e. the whole length of your lower limb). From this, your surgeon will be able to predict where currently your knee is bearing most of your body weight and how to appropriately realign your leg so as to achieve a successful outcome. It is likely that you will also have an MRI scan which will allow accurate assessment of the remaining cartilage throughout the knee joint and to assess associated ligaments and meniscus (shock absorbing cartilage).
Figure 4. X-ray of high tibial osteotomy using open wedge, plate and bone graft
Figure 5. X-ray of distal femoral osteotomy using open wedge, plate and bone graft
The option to perform a closing wedge or opening wedge osteotomy is at the discretion of the surgeon, with the decision being made based on what would be the best option for you with your particular condition.
You will be admitted to the hospital on the day of surgery. Your anaesthetist will discuss with you the most appropriate anaesthetic available to you and give you options for postoperative pain relief. At the time of surgery, you will be administered antibiotics to decrease the risk of infection. After your anaesthetic has been administered, a tourniquet will be applied to your upper thigh and everything except your knee joint will be covered in sterile drapes.
During the procedure, care is taken to protect the nerves and blood vessels that travel behind the knee joint. Commonly, a drain is inserted into the wound and is within 24 hours of surgery. All surgical incisions are closed using dissolving sutures. The leg will then be wrapped in a well-padded dressing prior to you leaving the operating theatre. Sometimes a brace is required for a short period after this type of surgery.
An x-ray of your knee will be performed in the recovery ward. Once you return to the ward a number of observations (temperature, blood pressure, heart rate, circulation and sensation to your feet) will be recorded at regular intervals.
Whilst in hospital, a physiotherapist will provide instructions on leg exercises that can be performed whilst in bed and also assist you in using crutches to walk. It is common to be on crutches with a closing wedge osteotomy for up to six weeks and occasionally up to 8-10 weeks with an opening wedge osteotomy as it takes longer for this type to heal. Your physiotherapy will focus on regaining knee movement, improving your mobility, and maintaining muscular strength around the knee joint. Additionally you will learn techniques to control the swelling in the knee. Once you are comfortable and are mobilising safely, your surgeon will allow you to be discharged home. The majority of patients discharged home within two days of the surgery. For the first month, your leg may be swollen and your knee may feel somewhat stiff. It is normal to require regular pain medication during this period. It is extremely important to perform your exercises regularly whilst at home to optimise your outcome following surgery.
It can take up to six months before you are fully rehabilitated after a knee osteotomy. The most important part of your rehabilitation is maintaining your strength and motion whilst the osteotomy is healing. It is important during this period that you are diligent with the exercises given to you by your physiotherapist. Physiotherapy generally starts within the first week of your operation.
In the ideal patient with the correct indications, an osteotomy is a good operation for reducing pain and improving knee function. It may delay the need for knee replacement surgery. The success of an osteotomy still providing good function and pain relief at five years is approximately 85%, 70% at ten years, and about 50% at 15 years.
When can I return to my normal sporting activities?
Most people after an osteotomy can return to sport somewhere between six to nine months. This will depend on your pre-operative level of activity, the severity of arthritis of your knee, as well as the progress you make with your rehabilitation.
When can I return to work?
If you work in an office setting it is possible that you may be able to return to work between two and three weeks, however if your occupation requires a lot of walking or heavy manual labour your return to work may be more prolonged, somewhere between six weeks and three months.
Will I need a knee replacement in the future?
An osteotomy has a good chance of delaying the need for a knee replacement in the future. Most people down the track will develop arthritis in other parts of the knee or have arthritis that progresses within the same compartment of the knee. When this occurs, you may require a total knee replacement.
Will I need further surgery after my osteotomy?
Most people who have an osteotomy require removal of the plates, commonly between one and two years after their operation. This is performed as a day operation and the recovery time is minimal. It is safest to have the plates removed at this time so that when surgery is performed in the future, there are no plates that could interfere with further treatment.
Will I have pain after an osteotomy operation?
Most people will have pain for 3-4 weeks after an osteotomy. This is generally well controlled with oral medication. Once the osteotomy fully heals it is expected that the majority of the arthritis pain symptoms will improve significantly as weight is carried on the healthier cartilage of the unaffected compartment.
What complications can occur from an osteotomy operation?
Sometimes complications can occur despite ever effort being made to avoid them. All due care is taken before, during and after the operation to try to ensure that complications do not arise. Should a complication occur, you will be informed and advised on the most appropriate treatment required to both address the complication and to optimise the outcome of the initial surgery.
The most common complications following knee osteotomy surgery are:
If you have any concerns or questions about this operation, please contact your surgeon at Sydney Knee Specialists on (02) 8307 0333
19 Kensington Street
Kogarah NSW 2217
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42-44 Urunga Parade
Miranda NSW 2228
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203-233 New South Head Road
Edgecliff NSW 2027
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