Total Knee Arthroplasty
What is it?
A total knee arthroplasty is a proven treatment option for arthritis involving the knee joint. It involves removing the arthritic surfaces of the end of the femur, top of the tibia and back of the knee cap (patella), and providing a new articular surface between a metal bearing and a plastic liner. The metal implants are cemented to the femur and the tibia.
Total knee arthroplasty became popular in the 1970's. The knee is now the most commonly replaced joint in the United States. Knee replacements have an excellent track record for improving the pain and functional limitations associated wth arthritis.
How is it performed?
A knee replacement is done through an incision on the front of the knee. The muscles are split and the quad tendon is not violated. The arthritic joint surfaces are removed and replaced with a metal and highly engineered plastic joint. The bottom of the femur (thigh bone) is resurfaced with metal, and the top of the tibia (shin bone) is resurfaced with plastic. The undersurface of the knee cap is also resurfaced with plastic.
Patients generally have the surgery peformed under a spinal anesthetic or sometimes under a general anesthetic. If you are able to undergo a spinal anesthetic, you will be lightly sedated and remain breathing on your own during the entire procedure. Most patients also have an additional nerve block placed to help numb portions of the knee to make the early recovery less painful.
The actual surgery takes around an hour. You will be in the surgical suite a bit longer while the anesthesiologist cares for you before and after the procedure. After surgery, you will spend an hour or so in the recovery room. When you are ready, the nurse will invite a family member or friend back to see you.
What are the risks?
Major medical complications are rare during the peri-operative period of a total knee replacement. We screen patients carefully to ensure that they are at a minimal risk for any of these complications. Aside from routine surgical and anesthetic risks (bleeding, infection, anesthesia side effects...), below are some of the most common risks associated with a knee replacement:
- Healthy patients have less than 1% risk of major complications. The risk can be increased if the patient is not in good health – in such cases I work with my medicine colleagues to develop a plan for minimizing the risk.
- The two most common surgical complications include infection (this may require further surgery) and blood clots (usually treated with strong blood thinners such as Coumadin).
- Knee stiffness can persist if range of motion is not achieved during the first 6 weeks after surgery. Replacing the knee will allow your knee to move normally. How much of the range of motion you keep is often determeined by how hard you work at physical therapy.
How do I know if I have knee arthritis?
Patients with knee arthritis often have pain in their knee that is typically worsened with activity. Some patients may feel occational popping or grinding in their knee with increased stiffness.
X-rays and examination are typically all that is needed to diagnose knee arthritis. These will demonstrate loss of the joint space in the knee and bone spur formation around the periphery of the joint as shown in these x-rays.
Knee replacement is also used as a treatment for secondary causes of arthritis such as post-traumatic arthritis as shown in the x-rays to the right.
What is the recovery like?
- Our goal is to help you get up and around as quickly as we can after surgery and to minimize the need for pain medications that could slow your progress. I find that the sooner patients are on their feet, the better they feel.
- While in the hospital, a physical therapist will help you get up a few hours after surgery. You will be allowed to put full weight on your leg. You will be taught to climb stairs prior to leaving the hospital.
- Most patients only need 1-2 nights in the hospital.
- My patients use a cane or walker as needed for the first several weeks. The early recovery is focused on getting your range of motion back. It is important that you get most of your range of motion by 6 weeks after the surgery.
- You will attend physical therapy to help with your range of motion and improve your gait and strength.
- The majority of the recovery is complete by 3 months after surgery although patients will continue to see improvements in their function beyond that.
What are the expected results?
The majority of patients are able to return to high levels of function after knee replacement with minimal to no pain. Many of our patients return to walking, hiking, golfing, tennis, cycling, and light aerobic activity. Other higher level activities such as longer distance running can be performed as well but can risk earlier wear of the replaced knee if performed regularly. In general, well placed knee replacements can be expected to last about 20 years or longer.
Who is not a good candidate for a total knee?
While a knee replacement generally provides predictably good results following surgery, there are some patients in which the results of a total knee replacement are less predictable. These include the following types of patients:
- Patients with severe spinal problems
- Patients on chronic pain medications
- Patients who actively smoke
- Patients in poor general health and physical conditionin
- Patients with a BMI over 40
- Patients with uncontrolled lower extremity edema.
While having any of these conditions does not mean that a total knee arthroplasty cannot be performed, it could mean that alternative methods of treatment may be safer and more predictable.