What causes a bow-legged or knock-kneed deformity?
As arthritis progresses, the cartilage of the joint wears thin. The meniscus, or joint cushions, are also damaged and wear away. If the damage is more on one side of the joint than the other, as is usually the case, then the knee will take on a deformed appearance. When the inside, or medial side, of the joint is worn thin, a varus deformity (bow-legged) will result. When the outside, or lateral side, of the joint wears thin, a valgus deformity results (knock-knees).
What is the problem with this type of deformity?
When the knee is worn more on one side, the forces transmitted across the joint are altered. When the inside (medial side) wears thin, the force of your body weight becomes more centered on the worn out part of the joint. Therefore, the healthier part of the knee is spared the burden of your body weight, and the damaged portion gets the brunt of your weight. This becomes a vicious cycle that leads to progression of the arthritis.
How does an osteotomy of the knee help?
The idea of an osteotomy is to shift the weight-bearing forces to "unload" the worn out side of the joint, and place the forces on the healthier side of the joint.
Who is an ideal candidate for a knee osteotomy surgery?
The problem with knee osteotomies is that finding the right patient is very difficult. Knee replacement surgery is very successful, and unless there is a good reason not to perform a replacement the total knee replacement is usually favored. Some patients, however, are not good candidates for knee replacement, especially patients who are young. Because knee replacements wear out over time, younger patients should be evaluated for alternative procedures.
The ideal patient for a knee osteotomy is a young, active person, who has arthritis limited to one side of the knee joint. The patient must have significant pain and disability such that surgery is warranted. The patient must understand that rehabilitation from this surgery is lengthy and difficult. Finally, osteotomies around the knee, tend to last less than one decade--then something more, usually a knee replacement, needs to be done. Some patients may find lasting relief with an osteotomy, but the majority of patients use a knee osteotomy surgery as a means to delay eventual knee replacement surgery.
Good candidates for this surgery must fit the following criteria:
- Significant pain and disability
- X-rays showing involvement of only one side of the knee joint
- The ability to cooperate with physical therapy and rehabilitation
Who is not a good candidate for a knee osteotomy?
Unfortunately, performing this surgery in the wrong patient can have poor outcomes. Therefore, you should discuss with your doctor the potential risks of this surgery. While many people want to avoid knee replacement surgery, the knee osteotomy is not right for everyone.
Patients generally should not consider this surgery if they have:
- Widespread arthritis of the knee (not confined to one side)
- Instability of the knee or tibial subluxation
- Significant limitations of knee motion
- Such a significant deformity it would be difficult to correct
- Inflammatory arthritis (such as rheumatoid arthritis)