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Knee surgery
The knee is a hinge joint consisting of three bones. The upper part of the hinge is at the end of the upper leg bone (femur), and the lower part of the hinge is at the top of the lower leg bone (tibia). When the knee is bent, the end of the femur rolls and slides on top of the tibia. A third bone, the kneecap (patella), glides over the front and end of the femur.
In a healthy knee joint, the surfaces of these bones are very smooth and covered with a tough protective tissue called cartilage. Arthritis causes damage to the bone surfaces and cartilage where the three bones meet and rub together. These damaged surfaces can eventually become painful.
There are several ways to treat the pain caused by arthritis. One way is total knee replacement surgery. The decision to have total knee replacement surgery should be made very carefully after consulting your doctor and learning as much as you can about the knee joint, arthritis, and the surgery.
In total knee replacement surgery, the bone surfaces and cartilage that have been damaged by arthritis are removed and replaced with artificial surfaces made of metal and a plastic material. We call these artificial surfaces "implants," or "protheses."
What to Bring to the Hospital
Below is a list of things you may want to bring with you to the hospital in preparation for your surgery. Talk with your physician as he/she may have additional information about preparing for your hospital stay.
- Your personal belongings should be left in the car until after surgery. Tell your family that your room will be assigned when you are in surgery or in recovery, at which point they can bring your personal items to your room.
- Personal grooming items that you may want to pack include a toothbrush, toothpaste, hairbrush, eyeglasses/contacts, comb, deodorant, shaving cream/electric razor, shampoo, lotion, undergarments, and a robe.
- Bring slippers or flat rubber-soled shoes for walking in the hallways.
- Bring loose fitting clothing for your trip home.
- Bring any medications you are currently taking. You should also write down your medication information to be given to the hospital staff. Be sure to include the name, strength, and how often you take the medications. Please communicate any allergies you might have to your doctors and the nursing staff.
- If you use a breathing exerciser (IBE), be sure to bring it with you from home, as you will probably need this right after surgery.
- Leave jewelry, credit cards, car and house keys, checkbooks, and items of personal value at home. Bring only enough pocket money for items such as newspapers, magazines, etc.
Getting to the Joint
The patient is first taken into the operating room and given anesthesia. After the anesthesia has taken effect, the skin around the knee is thoroughly scrubbed with an antiseptic liquid. The knee is flexed about 90 degrees and the lower portion of the leg, including the foot, is placed in a special device to securely hold it in place during the surgery. Usually a tourniquet is then applied to the upper portion of the leg to help slow the flow of blood during the surgery.
An incision is then made that typically extends from just above the knee to just below the knee. The incision is gradually made deeper through muscle and other tissue until the bone surfaces are exposed.
Removing the Damaged Bone Surfaces
The damaged bone surfaces and cartilage are then removed by the surgeon. Precision instruments and guides are used to help make sure the cuts are made at the correct angles so the bones will align properly after the new surfaces (implants) are attached.
Small amounts of the bone surface are removed from the front, end, and back of the femur. This shapes the bone so the implants will fit properly. The amount of bone that is removed depends on the amount of bone that has been damaged by the arthritis.
What can I expect after surgery?
When you are back in your hospital room, you will begin a rehabilitation program that will help you regain strength, balance, and range of movement in your knee. This program will be designed specifically for you. It may include a machine, called a continuous passive motion machine that automatically moves your leg to help reduce stiffness.
Your physical therapist will help you perform appropriate exercises. About 24 hours after surgery, you will probably be asked to stand. Within the next 24 hours, you will probably begin to walk a few steps with the help of a walker. You will be discharged as soon as your surgeon determines that you have recovered sufficiently. You can expect to stay in the hospital for about three days after your surgery. You may or may not be transferred to a rehabilitation facility for a few more days, as determined by your surgeon. Your bandages and sutures will usually be removed before you leave the hospital. At home, you will need to continue your exercises. Your physical therapist will instruct you about proper home care, and may continue to work with you.
A small portion of the top surface of the tibia is also removed, making the end of the bone flat.
The back surface of the patella (kneecap) is also removed.
Attaching the Implants
An implant is attached to each of the three bones. These implants are designed so that the knee joint will move in a way that is very similar to the way the joint moved when it was healthy. The implants are attached using a special kind of cement for bones.
The implant that fits over the end of the femur is made of metal. Its surface is rounded and very smooth, covering the front and back of the bone as well as the end.
The implant that fits over the top of the tibia usually consists of two parts. A metal baseplate fits over the part of the bone that was cut flat. A durable plastic articular surface is then attached to the baseplate to serve as a spacer between the baseplate and the metal implant that covers the end of the femur.
The implant that covers the back of the patella is also made of a durable plastic.
Artificial knee implants come in many designs. Some designs may have pegs, requiring small holes to be drilled into the bone after the damaged surfaces have been removed. Others may have central stems. In addition, some designs may allow screws to be used on the lower implant to provide added attachment security. The surgeon will choose the implant design that best meets the patient's needs.
Closing the Wound
If necessary, the surgeon may adjust the ligaments that surround the knee to achieve the best possible knee function.
When all of the implants are in place and the ligaments are properly adjusted, the surgeon sews the layers of tissue back into their proper position. A plastic tube may be inserted into the wound to allow liquids to drain from the site during the first few hours after surgery. The edges of the skin are then sewn together, and the knee is wrapped in a sterile bandage. The patient is then taken to the recovery room.
