How Does a Knee Get Replaced?

How do they Replace a Knee?

Knee replacement surgery is performed due to chronic knee pain and loss of mobility. According to the Center for Disease Control and Prevention (CDC), in 2010 alone, almost 700,000 total knee replacements were performed on adults age 45 years and older. Total knee replacement (TKR) has nearly doubled in prevalence over the last couple of decades, especially for women (a 99% increase).

Steps in a Total Knee ReplacementKnee pain 3

Step 1: Administering anesthesia – Knee replacement surgery is usually performed with you under general anesthesia. The doctor will discuss this with you before the surgery. You will be given medications through an intravenous (IV) catheter, and an intubation tube will be placed in your airway.

Step 2: Prepping the knee – After all excessive hair over the knee is clipped or shaved, the skin over the knee is cleaned with an antiseptic solution.

Step 3: Making incision – The orthopedic surgeon will make a 4- to 6-inch incision in the knee area.

Step 4: Removing damaged surfaces – The damaged knee joint and surface will be removed. This involves specialized instruments used to remove cartilage and bone pieces from the joint.

Step 5: Insert prostheses – The artificial components are made of plastic and metal. Most artificial knee components are cemented into the joint. The prosthesis attaches to the bone using a special cement. The components include a tibial component (resurface top of tibia or shin bone), a femoral component (resurfaces end of femur or thighbone), and a patella component (resurfaces the patella or kneecap).

Step 6: Checking motion and implants – After the implants are in place, the surgeon checks range of motion and prostheses stability.

Step 7: Closing incision – The incision is closed using surgical staples or sutures. Depending on the situation, a tiny catheter with drain may be placed in the incision to remove fluid. A sterile, dry bandage dressing is applied over the knee.

How Long does a Total Knee Replacement Last?

A common reply to this question is that a total joint replacement typically lasts 15-20 years. Most current data suggest that both knee and hip replacements have an annual failure rate of around 0.5%. This means that if you have a total knee replacement today, you have a 95% chance of it lasting 10 years, and an 85% chance that it will last 20 years.

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Types of Implants

The orthopedic implant industry has continued to develop innovative technologies to improve the outcomes of total knee replacement. However, many studies show that there is no clear advantage of any of these designs in relation to improving clinical outcomes. Some designs are:

  • Gender specific – This refers to a modified implant design that accounts for the anatomic difference between women’s and men’s knees. Most companies have some modifications in these designs to allows for sizing options so the prosthesis will fit accurately in relation to the patient’s anatomy.
  • Rotating platform – This refers to a plastic component that independently rotates on a metal tray. The plastic bearing will lock into the tray, and was designed to reduce wear on the bearing. In addition, this device can reduce the rate of loosening of metal components and better replicate the normal knee function and movement.
  • Computer technology – There are studies that have evaluated the emerging technologies in knee replacement surgery along with the success of the procedure using computer technology. Computer, robot, and custom cutting guides are used for accuracy in implant placement, as well as a more efficient surgery.

Resources

Center for Disease Control and Prevention (2015). Hospitalization for Total Knee Replacement Among Inpatients Aged 45 and Over: United States, 2000–2010. Retrieved from: http://www.cdc.gov/nchs/data/databries/db210.htm

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