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
Who is suitable for an osteotomy?
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
What are the main reasons for performing an osteotomy?
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).
What are the main types of osteotomy around the knee joint?
- High Tibial Osteotomy (HTO)
This is the most common osteotomy performed around the knee, and is often performed using an opening wedge technique (see below). It is used when there is OA on the medial (inner) side of the knee. Most often, an opening wedge is created on the medial side of the upper tibia to push the weight on to the outer (lateral) compartment of the knee. [Figure 4]
- Distal Femoral Varus Osteotomy (DFVO)
This is used when there is arthritis on the outer (lateral) compartment of the knee. In order to transfer the pressure to the healthier medial side, an opening wedge is made on the lateral part of the lower femur bone. [Figure 5]
Figure 5. X-ray of distal femoral osteotomy using open wedge, plate and bone graft
- Tibial Tubercle Osteotomy (TTO)
This osteotomy is used for arthritis or instability of the patellofemoral joint. This operation is discussed in more detail under the section on Patellofemoral Instability.
How is an Osteotomy Performed?
- Opening wedge osteotomy – in this technique a surgeon cuts through the upper tibia (just below the knee joint) on the medial side and opens a wedge, sometimes adding a piece of bone (auotgraft) taken from the pelvic area or using cadaveric bone (allograft) to hold the wedge open and facilitate healing. In order to stabilise this, a plate is inserted across the osteotomy. This is the commonest technique used at Sydney Knee Specialists, as it does not shorten the leg, and also reduces the complexity of future knee replacement surgery. This has the effect of shifting your body weight from the inner part of the knee to the non-affected lateral compartment.
- Closing wedge osteotomy – this involves removing a wedge of bone usually just below the joint in the upper part of the tibia. For patients with arthritis affecting the medial compartment (varus knees) the bone wedge is taken from the outer part of the tibia. Once the wedge of bone is removed the two bone ends are then put together and held with either a metal plate or staples. This also has the effect of shifting your body weight from the inner part of the knee to the non-affected lateral compartment.
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.
What does the operation involve?
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.
After your operation
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.
Frequently asked questions
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:
- Infection – the risk of infection following this procedure is very uncommon (<1 in 100). This can either be a superficial (minor) infection involving the incisions, or a deep infection involving the knee joint and bone. If this occurs, antibiotics will be required. If it is a deep infection, admission to hospital is required as are intravenous antibiotics. If the infection involves the knee joint, a knee arthroscopy may be required to wash the infection out. Antibiotics are given prior to the operation to reduce the risk of infection. There is a higher infection risk in smokers and as such it is critical that you cease smoking approximately two weeks prior to your surgery. It is also important to prevent any cuts, rashes or abrasions developing around the knee joint prior to surgery as they increase the risk of infection, and your surgery will have to be delayed until they have resolved.
- Blood clots “Deep Venous Thrombosis” – the risk of developing a blood clot in a calf muscle vein is approximately 1 in 20. Very rarely these blood clots can break away and travel to your lungs. This is called a “pulmonary embolus”. The risk of developing a pulmonary embolus is exceedingly rare. If you develop calf pain or tenderness following your surgery, you should contact your surgeon or family doctor and notify them of this. An ultrasound examination will be performed of the calf to assess for a blood clot. Medications will be required to prevent these blood clots from getting larger. To minimise the risk of a blood clot, it is important to notify your surgeon if you have any hereditary risk factors for blood clot formation, or if you have experienced a blood clot in the past. You should also cease smoking as this increases the risk of this complication. The combination of the oral contraceptive pill or HRT with smoking increases the risk of DVT as well. These factors should be discussed with your surgeon prior to your operation.
- Failure of the osteotomy to heal – About 3-5% of people experience problems with the bone healing. Occasionally, this requires more surgery including bone grafts taken from the pelvis and further plate fixation. The risk of this complication is reduced be cessation of smoking and strict compliance with your post-op rehab.
- Fractures adjacent to the osteotomy – Occasionally, a crack (fracture of the bone) can develop adjacent to the osteotomy. Often this is recognised at the time of the operation and treated. Sometimes, this only becomes apparent on subsequent x-rays. If this does occur, additional surgery may be required.
- Nerve Injury – There is a very rare complication but can result in either numbness, or loss of power of the muscles that move the foot and ankle (foot-drop). In most cases, this is temporary and resolves over 6-12 months. It is important to note that this is different to the usual numbness that occurs around the surgical incisions with most types of surgery (see pt 7 below)
- Compartment Syndrome – This is where pressure develops in the leg from swelling and reduces blood flow to the muscles. It occurs usually within the first 48 hours of surgery. If not treated with decompression (fasciotomy), it can result in permanent damage to muscle. The risk of this complication is less than 1 in 1,000.
Numbness around the cuts – It is common to have numbness around the surgical incisions. Most of these small patches are temporary and do not bother patients. Occasionally a permanent patch of numbness can be experienced at the upper part of the tibia on its outer side.
- Stiffness – There is a risk of developing knee stiffness following the surgery. If this occurs, you may require a second operation where the knee is either manipulated or scar tissue is removed from the inside of the knee joint. In order to prevent stiffness following the operation, it is important to have good range of motion prior to surgery and perform regular stretching exercises. Most importantly, you must actively participate in the post-operative rehabilitation program under the care of your physiotherapist.
- Hardware related-complications – As metal plates and screws are required to hold the osteotomy in position, these may become prominent and cause irritability of either the skin or tendons. This is often is resolved once the plate and screws are removed. Your surgeon will often recommend removing the metal plate and screws at around the 1-2 year mark post-op.
- Ongoing swelling or pain – As this surgery is performed for arthritis, there are some patients who do not experience significant improvement in arthritic symptoms despite the operation being carried out correctly and with all due professional care. In addition, not all patients are able to return to high-impact activities despite having relief in symptoms during normal activities. Your surgeon will recommend to you whether it is feasible for you to return to high impact activities in the future.
If you have any concerns or questions about this operation, please contact your surgeon at Sydney Knee Specialists on (02) 8307 0333