Correction of Knock-Knees
Knock-knees may cause knee pain and limitations, especially as we grow older. The medical term used to describe this problem is valgus and it indicates a malalignment of the lower extremity. Some people are born with knock-knees, but others may develop the problem in just one leg following an injury. The main problem with knock-knees is that osteoarthritis may develop in the outer (lateral) area of the knee, causing pain, swelling, and limitations with recreational sports and eventually, problems with normal activities of daily living. This may be worsened with obesity or overuse of the knee joint, and can become a serious problem if the lateral meniscus (cartilage) is removed.
Osteoarthritis may occur from knock-knees because there is an abnormal amount of stress and pressure placed on the outer portion of the knee joint. A good analogy to this problem is the wearing of a portion of a tire on a car that is out of proper alignment. If the alignment is not fixed, the tire will wear out on one side, shortening its expected lifespan.
Technically, the term osteoarthritis refers to damage to the articular cartilage in the joint. Articular cartilage is a protective layer of tissue located on the ends of bone that come together in the knee, which are the femur (thigh bone), tibial (shin bone), and patella (kneecap). There is a second type of cartilage in the knee called a meniscus. There are 2 menisci in the knee – a medial (inner) and a lateral (outer). Each meniscus is an important tissue that acts as a cushion between the femur and tibia.
Below is a photograph taken during arthroscopic surgery of a knee with normal articular cartilage surfaces and a normal meniscus.
Now, take a look at the next photograph of a knee with severe damage to the articular cartilage and no meniscus tissue left due to a prior operation in which it was removed. This severe damage requires a knee replacement operation.
Distal Femoral Osteotomy for Knock-Knees
Fortunately, there is an operation for knock-knees that has gained wide acceptance as a treatment option for younger or athletic patients with osteoarthritis in the outer portion of the knee. An operation called a distal femoral osteotomy may be performed in which bone in the femur just above the knee is cut and the leg is properly aligned by the surgeon. Often, patients who require this operation are young and have had their lateral meniscus removed and already have early signs of arthritis. Below is a photograph of a patient with a valgus malalignment of the left knee. This was an unusual case of a patient who had undergone an osteotomy elsewhere that was too excessive and created the valgus problem.
Patients should be aware that this procedure produces a surgical fracture of bone and must be treated carefully for 7 to 8 weeks to allow healing into the new corrected position. The patient must accept the goals of the osteotomy, which are to allow an active, pain-free lifestyle for a certain amount of time that includes low-impact recreational sports, but not high-loading activities involved with twisting, turning, jumping, and pivoting. The knee arthritis will eventually progress and therefore, the goal is to buy as much time as possible in younger patients before a partial or total joint replacement is required.
Special standing x-rays are taken before surgery and will be shown to you to see how the surgeon will align the knee joint into a more correct load-bearing alignment.
The indications for femoral osteotomy for knock-knees are:
- Age less than 50
- Lateral compartment articular cartilage damage, but not down to bone
- Lateral joint pain with activity
- knock-knees with knee ligament injury, before a ligament reconstruction
- Before a meniscus transplant or articular cartilage procedure (see the Cartilage Repair section of this website for further information on cartilage repair procedures)
The contraindications to HTO are:
- Lateral tibiofemoral compartment bone exposed > 15 mm x 15 mm area
- Prior medial meniscectomy or medial tibiofemoral compartment articular cartilage damage
- Symptomatic patellofemoral arthrosis
- Lateral compartment depression and concavity preventing medial compartment loading
- Poor patient motivation or unrealistic expectations
- Prior joint infection, diabetes, rheumatoid arthritis, autoimmune diseases, malnutrition
- No joint space left in the lateral compartment
Only a few long-term clinical studies have been published on the outcome of distal femoral osteotomy. Four studies followed 136 patients who received a closing wedge femoral osteotomy for 10 years postoperatively. These investigations found the following survival rates (meaning the patients were doing well and had not required total knee replacement): 90%, 87%, 82%, and 64%. To date, 3 studies reported 15-year survival rates after this procedure of 45%, 49%, and 79%.
Two studies provided 7-year survival rates after opening wedge femoral osteotomy in 41 patients of 82-91%. We expect in the near future for more data to be published because this technique has gained favor with many surgeons over the last several years. Considering the fact that this operation’s goal is to buy time and provide pain relief with regular daily activities until total knee replacement is required, the 7 and 10-year survival rates justify its use in correctly indicated patients.
Frequently Asked Questions
1. How has femoral osteotomy changed over time to reduce the complication rates and improve the success rates?
There have been several factors in preoperative planning, operative techniques, and postoperative rehabilitation that have made a real difference in the results of femoral osteotomy. These include increased precision in the calculations required to achieve the desired angular correction, such as the use of computerized navigation and special x-rays taken throughout the operation to ensure the knock-knee malalignment is corrected. Smaller incisions are used, with less dissection of tissues which means a less invasive operation. The fracture site is secured with a high strength locking plate that allows earlier partial weight-bearing. These plates also decrease the problems with healing of the fracture sites, known as nonunion or delayed union.
2. What are the overall success rates of femoral osteotomy?
Overall, we have noted that 70-80% of patients have a significant improvement in their symptoms and knee function. Many can return to recreational sports that allow an active lifestyle for many years after surgery. The majority can do their daily activities without problems. However, we always advise our patients that if there is already arthritis in knee joint that it will progress. About 20% of patients will not have a long-term benefit and may require a partial or total knee replacement.
3. Why is it necessary to bone graft the wedge (or gap) in an opening wedge femoral osteotomy?
In opening wedge femoral osteotomies, a space or gap is created in the femur. This gap must be filled with bone or the angular correction will collapse. The bone comes from the patient’s hip through a small, 2-inch incision. This procedure does make the initial few postoperative weeks somewhat uncomfortable, but our experienced medical staff knows how to help manage pain and swelling through the use of appropriate medications, rest, ice, and elevation of the limb.
5. What is rate of nonunion that requires subsequent surgery?
In our experience, no further bone grafting or surgery for bone healing problems has been required. We believe this was due to the type of fixation we used to stabilize the fracture site. We do inform patients that there is a 1-5% chance of a delayed union that requires the patient to spend a longer amount of time on crutches.
6. Overall, how advantageous is it to correct knock-knees?
We and many other orthopaedic centers believe it is very advantageous to have an osteotomy for a painful knock-knee condition. Studies have shown that femoral osteotomy buys many years before patients need further surgery such as a partial or total knee replacement. This is particularly helpful in younger patients who wish to remain active and avoid knee replacement for as long as possible. Patients who require a lateral meniscus transplant or articular cartilage restoration procedure need to have the knock-knee malalignment corrected first or the other procedure will most likely fail.
7. How soon will I start rehab?
In our clinic, patients begin rehabilitation the first day after surgery. It is very important during the first week to control pain and swelling, which may be done with appropriate medications, ice, and elevation of the limb. It is also important to “turn on” the muscles in the leg which may be accomplished with the assistance of modalities (such as electrical muscle stimulation) guided by a physical therapist. The early start of knee motion and muscle strength exercises reduces the risk of complications such as excessive scarring and muscle atrophy. Our rehabilitation program lasts for 6 months, but most of the exercises may be done at home or in a fitness facility.