What is Knee Osteoarthritis?
Osteoarthritis of the knee is the most common joint disease in the world. Cartilage is a soft material which acts as a cushion between our joints. Osteoarthritis is caused when this cartilage in a joint is worn down over time. This results in the bones rubbing against one another, causing pain and stiffness. This can be due to a number of factors, with age and physical activity being among the most common.
In the knee, the loss of cartilage eventually leads to a misalignment of the leg due to an uneven weight load on one side of the knee joint, exacerbating these symptoms. The name of this alignment is called the mechanical axis. If it becomes misaligned, the affected leg will start bowing to one side.
What causes it?
When walking, much of the load is placed on the inside of the knee, due to the knees naturally ‘bowing’ slightly away from one another. This causes a greater amount of wear and tear on the cartilage on the inside of the knee. When combined with other factors such as age, this cartilage can become damaged, resulting in the bowing becoming progressively worse as the bones become closer together on the inside than the outside of the joint. This in turn leads to more stress and more damage, creating a cycle that ends in osteoarthritis. An attractive option in this case is to modify the joint to more equally distribute the weight across the knee, rather than replacing the entire knee with an artificial joint; this surgical procedure is called High Tibial Osteotomy (HTO). It involves a cut into the top of the shin bone (tibia) which is slightly opened to change the leg’s structure, resulting in a less bowed leg and more weight carried by the healthier tissue.
The symptoms of osteoarthritis include:
- Grating sounds when moving
- Difficulty moving the affected joint
HTO is a knee-preserving alternative to join replacement
As well as reducing pain and stiffness, this procedure has several other advantages. Perhaps the most attractive benefit of this procedure compared to a total or partial knee replacement is that preserving the natural joint allows for more normal use of the knee following surgery. This includes activities that would usually be unlikely after knee replacement, including sport!
HTO is, therefore, a joint preserving surgical treatment. Unlike knee replacement where the joint surface is permanently removed to host the artificial implant, in a well performed HTO the bone will regrow, and the reduced load often allows the damaged cartilage to regenerate.
Where knee replacement often leads to a sedentary lifestyle and associated other health conditions, HTO can allow greater activity levels with the associated benefits of activity. Depending on age and level of activity, a knee replacement may need to be replaced after 10 to 15 years of use, requiring a ‘revision’ or follow-up operation, resulting in a greater risk of infection or complications.
"For younger and active patients, HTO is an attractive alternative to partial knee replacement (UKR) but also to total knee replacement (TKR)."