Knee Replacement Surgery: Step by Step Explanation

A knee replacement is a complex procedure that requires an orthopedic surgeon to make precise measurements and skillfully remove the diseased portions of your bone, in order to shape the remaining bone to accommodate the knee implant.

What is knee replacement surgery?

Knee replacement, also called knee arthroplasty or total knee replacement, is a surgical procedure to resurface a knee damaged by arthritis. Metal and plastic parts are used to cap the ends of the bones that form the knee joint, along with the kneecap. This surgery may be considered for someone who has severe arthritis or a severe knee injury.

Various types of arthritis may affect the knee joint. Osteoarthritis, a degenerative joint disease that affects mostly middle-aged and older adults, may cause the breakdown of joint cartilage and adjacent bone in the knees. Rheumatoid arthritis, which causes inflammation of the synovial membrane and results in excessive synovial fluid, can lead to pain and stiffness. Traumatic arthritis, arthritis due to injury, may cause damage to the cartilage of the knee.

The goal of knee replacement surgery is to resurface the parts of the knee joint that have been damaged and to relieve knee pain that cannot be controlled by other treatments.

Reasons for the procedure

Knee replacement surgery is a treatment for pain and disability in the knee. The most common condition that results in the need for knee replacement surgery is osteoarthritis.

Osteoarthritis is characterized by the breakdown of joint cartilage. Damage to the cartilage and bones limits movement and may cause pain. People with severe degenerative joint disease may be unable to do normal activities that involve bending at the knee, such as walking or climbing stairs, because they are painful. The knee may swell or "give-way" because the joint is not stable.

Other forms of arthritis, such as rheumatoid arthritis and arthritis that results from a knee injury, may also lead to degeneration of the knee joint. In addition, fractures, torn cartilage, and/or torn ligaments may lead to irreversible damage to the knee joint.

If medical treatments are not satisfactory, knee replacement surgery may be an effective treatment. Some medical treatments for degenerative joint disease may include, but are not limited to, the following:

• Anti-inflammatory medications
• Glucosamine and chondroitin sulfate
• Pain medications
• Limiting painful activities
• Assistive devices for walking (such as a cane)
• Physical therapy
• Cortisone injections into the knee joint
• Viscosupplementation injections (to add lubrication into the joint to make joint movement less painful)
• Weight loss (for obese persons)
• There may be other reasons for your doctor to recommend a knee replacement surgery.

Risks of the procedure

As with any surgical procedure, complications can occur. Some possible complications may include, but are not limited to, the following:

1. Bleeding
2. Infection
3. Blood clots in the legs or lungs
4. Loosening or wearing out of the prosthesis
5. Fracture
6. Continued pain or stiffness

The replacement knee joint may become loose, be dislodged, or may not work the way it was intended. The joint may have to be replaced again in the future.

Nerves or blood vessels in the area of surgery may be injured, resulting in weakness or numbness. The joint pain may not be relieved by surgery.

There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.

1. Making the knee incision

The surgeon makes an incision across the front of your knee to gain access to the patella, more commonly referred to as the kneecap. In a traditional knee replacement, the incision is usually about 8 to 10 inches long. In minimally invasive knee surgery, the incision is usually about 4 to 6 inches long. The jury is still out as to whether or not the pros of the smaller scar outweigh the cons of a smaller surgical area. Talk to your doctor about which procedure is right for you.

2. Rotating the patella (kneecap)

The first part of your knee that is exposed is your kneecap, called the patella. Once your knee is open, the surgeon rotates the patella outside the knee area. This allows the surgeon to view the area needed to perform the surgical procedure.

3. Preparing the femur (thighbone)

The first bone your surgeon will resurface is your femur, commonly known as the thighbone. Once the surgeon has opened up and exposed your knee joint, he or she will carefully measure your bones and make precise cuts using special instruments. The damaged bone and cartilage from the end of the femur is cut away. The end of your femur is cut and resurfaced to fit the first part of the artificial knee, the femoral component.

4. Implanting the femoral component

The surgeon attaches the metal femoral component to the end of your femur and uses bone cement to seal it into place.

5. Preparing the tibia (shinbone)

The next bone your surgeon resurfaces is your tibia, or shinbone. The surgeon removes damaged bone and cartilage from the top of the tibia and then shapes the bone to fit the metal and plastic tibial components.

6. Implanting the tibial component

The bottom portion of the implant, called the tibial tray, is fitted to the tibia and secured into place using bone cement. Once the tray is in place, the surgeon will snap in a polyethylene (medical-grade plastic) insert to sit between the tibial tray and the femoral component, and act as a kind of buffer. This insert will provide support for your body as you bend and flex your knee.

7. Re-adjusting the patella

Before returning the patella to its normal position, the surgeon might need to flatten the patella and fit it with an additional plastic component in order to ensure a proper fit with the rest of your implant. The plastic piece, if needed, is cemented to underlying bone.

8. Finalizing the procedure

Your surgeon will bend and flex the knee to ensure that the implant is working correctly, and that alignment, sizing, and positioning is suitable. To complete the procedure, the surgeon will close the incision with stitches or staples, and then bandage it and prep you for recovery. You may leave the operating room with your leg in a continuous passive motion (CPM) machine that will gently bend and flex your new knee for you while you are lying down.

July 26, 2019