What is Involved in Knee Replacement Surgery?
Let’s face it, the unknown of an upcoming knee replacement is scary. What is involved in a total knee replacement? What are my options? What decisions do I need to make beforehand? We think knowledge is power, so read on and get better informed about your upcoming knee replacement surgery.
Arriving at the point of requiring knee replacement surgery is becoming more common than ever before. Every year, greater numbers of Americans—young and old—are undergoing knee replacement surgery. In fact, the CDC reported a record high of 719,000 total knee replacements last year alone. This figure does not include partial knee replacements which are estimated to account for an additional 5-10% more surgeries.
These figures also don’t represent the enormous short and long-term success of the knee surgery. According to numerous studies, the patient satisfaction rate for a total knee replacement is among the highest of any orthopaedic procedure, sitting between the 80-90+% mark. Additionally, 10 years after surgery, 90-95% of implants are still fully functional.
What is a Total Knee Replacement (TKR)?
More than 90% of annual knee replacements are total knee replacements (TKR). As the name suggests, in a total knee replacement all of the cartilage and bone that has been damaged from osteoarthritis (or otherwise) is resurfaced. In this resurfacing the damaged cartilage and small amounts of bone are removed. The healthy bone is left intact to support the new artificial joint. Up to three parts of the knee may be replaced with artificial components. These components are generally composed of two metal implants articulating on a plastic insert. The brand, design and material of the artificial joint replacement you receive is determined by the hospital, doctor, and other factors like the amount of damage to your knee, your weight, activity level and so forth.
The end result of this knee surgery is a highly realistic and functional replacement that is fitted to your healthy knee bone. The implant will either be secured with surgical cement, be “uncemented” and “press-fitted” to rough-surface bone (in which the bone will organically grow into it) or some combination of the two.
A partial knee replacement (PKR) is significantly less popular than a total knee replacement (TKR). In a partial knee replacement, one or more parts of the knee is replacement by artificial components, while the working parts of the knee are left as-is. If two or more parts of the knee need replacing, a TKR is usually the preferred approach.
3 Components in an Artificial Knee Implant
* Image from http://orthoinfo.aaos.org/topic.cfm?topic=A00712
- Tibial component- A flat part that attaches to the top of the resurfaced shin bone at the front of the leg (tibia)
- Femoral component- The largest, curved part that attaches to the end of the resurfaced thighbone (femur).
- Patellar component-A dome-shaped piece that replaces the damaged knee cap that rubs against thighbone.
Different Approaches for Total Knee Replacement: Traditional vs. Minimally Invasive
The traditional approach involves an 8-10mm vertical incision that runs down the center of the knee. This incision is the access point to resurface the knee and rebuild the artificial joint.
70-80% of patients have their knee replaced with the traditional technique.
The minimally invasive total knee approach (sometimes called “quadriceps-sparing” approach) involves a nearly identical procedure with a couple of exceptions: a shorter incision is made on the patient, a less intrusive technique is used to access the joint, and the operation is more challenging and lengthier for the surgeon.
With this approach, less tissue is cut around the knee and the incision is about 4-6 inches long with a general aim to leave the quadricep tendon and muscle untouched. The artificial knee components (tibial, femoral and/or patellar) are the same with a minimally invasive approach, only the tools used by the surgeon to perform the procedure are different.
As a result, the minimally invasive procedure can mean a faster recovery as less tissue, muscle and tendon are affected. It can also reduce recovery pain levels and hospital stay length. Although there are pros for the minimally invasive, it is still a relatively new technique with less available statistics surrounding long-term success. Unlike the catch-all traditional approach, the minimally invasive approach is not for everyone.
The minimally invasive technique is less suitable for:
- Those who are overweight
- Those who’ve undergone a previous knee surgery
- Those with significant osteoarthritis/ knee damage
- Those who are very muscular
Step-by-Step Guide to Total Knee Replacement Procedure
So, what is involved in a knee replacement operation?
The moment you’ve been waiting for/dreaming about/dreading/panic-stricken over is going to take somewhere between 60-90 minutes. In this short time, your surgeon will be ridding your body of the old, problem-causing knee bone and cartilage and replacing it with components that will make up a your new high-tech joint.
Before you get to surgery day, it’s hugely important that you’ve had a chance to physically and mentally prepare. This means you’ve undergone a prehab program to optimize your health and reduce your risk. This also means you’ve taken care of key “housekeeping” tasks like: knowing the type of anesthetic that you’ll be getting (general or a nerve block), preparing your home for your post-surgery arrival, and addressing all of your outstanding questions or concerns in your pre-op visit.
Did you know? Nerve blocks are less risky and can actually decrease your recovery time from surgery.
Assuming you’ve crossed all of your t’s and dotted your last i, let’s jump to surgery day.
Here is a play by play of what your joint replacement will more or less look like:
- “Let the Games Begin”- Before surgery, all of your vital signs (like heart rate and blood pressure) will be checked. The surgeon will mark up your surgical leg and then anesthesia will be administered. After this, it’s go time!
- “The Incision”- Depending on the approach you and your surgeon have decided to go with, an incision about 8-10 inches in length or one approximately half of that size will be made across the front of your kneecap. This incision is made to gain access to behind your knee cap (also known as patella) where all of the action will take place.
- “Access Granted: Open the Knee”- Okay, this part is a bit cringeworthy. Next up: your knee cap is flipped outside the knee area. This allows the surgeon a way in to view the area being resurfaced and to actually perform the procedure.
- “Everybody, Femur Time”- The upper thigh bone (also known as the femur) is usually the first bone to be resurfaced. The damaged cartilage and a little bit of diseased bone is removed. The remaining bone is shaped and measured to perfectly fit the femoral component implant. Your surgeon will use either a metal jig or a computer-assisted program to make the proper cuts and shapes to your bone. Your surgeon will then attach the femoral component, most likely cementing it into place with bone cement. Alternatively, the implant could be press-fit to the bone. The femoral component is the largest part in your artificial knee.
- “Tinker with the Tibia”- The upper tibia (also known as the tibia) is up next. Similarly, your surgeon will remove the damaged cartilage along with some bone, and shape and cut the healthy bone to fit the tibial implant. This implant is sometime called the “tibial tray” and is typically attached using bone cement.
- “Plastic Space Cadet”- Once both the femoral component and tibial component are attached, an insert is snapped into place between the two pieces. This flexible plastic spacer provides a smooth, gliding surface for your new knee joint to bend and flex.
- “A Feather in Your (Knee) Cap”- This step depends on the individual. Often the kneecap is resurfaced in order to properly fit the new implant. However, this is not always the case. If necessary, the kneecap will be flattened and cemented with a final button or dome-shaped patellar component that will perfect the fit and function of the whole implant.
- “Flex, Fit, Finale”- Before putting your kneecap back in place, your surgeon will test the motion, flexibility, extension and fit of the implant. Once the surgeon is confident in your range of motion, your incision will be closed with stitches or staples then wrapped up in bandages.
Immediately after surgery, we hope you can relish in the fact that you’ve done a great thing for your health and quality of life. Although recovery will undoubtedly have some trying moments, the more you prepare beforehand through prehab, understand the procedure to its fullest, and surround yourself with a network of support, the faster and easier it will be.
Sign-up for PeerWell’s PreHab app to gain full access to our scientifically-proven PreHab program. Join a team of supportive peers who are undergoing a knee replacement at the same time as you today.
This post was reviewed by Dr. Nima Mehran, MD, Orthopaedic Surgeon.