Hip Preservation Clinic

Total Knee Arthroplasty

When the knee joint can no longer be benefited by nonsurgical treatments such as injections, physical therapy, lifestyle modifications and ambulatory aids, and when arthroscopic surgery no longer helps, a knee replacement surgery may be the best treatment option.

The knee joint is a gliding joint that can be thought of as a hinge and platform. The top part of the knee joint is the end of the femur (thigh bone), and this hinges on the tibial plateau (top part of the shin bone). The knee is surgically divided into three compartments: the medial (inside of the knee/closer to center of the body), the lateral (outside of the knee), and the patellofemoral compartment (behind the knee cap and in front of the end of the femur). When only one compartment is affected by arthritis (uncommon), and all of the ligaments (connect the bones together) function well, you may be a candidate for a partial knee replacement; however more commonly, the arthritis exists in multiple compartments, and a total knee replacement is the most complete option for symptomatic knee arthritis. Your surgeon will make a recommendation based on which type of knee replacement is best for you considering the risk of progression of arthritis in less affected compartments. The goal of this would be to reduce the long term need for additional invasive surgeries depending on your goals, surgical risks and current limitations. 

Total knee replacement surgery starts with removing the ends of the bones where the arthritis exists and creating flat surfaces for the implants to adhere/affix. Usually this entails a flat cut of the tibia to make this even, and then several cuts on the femur since the end of the femur has two humps called condyles. 

The femur is usually cut in 4 places to create flat surfaces. These are the anterior, posterior, anterior chamfer, and posterior chamfer cuts. These are precisely set according to a jig, which is matched with an implant so that the cuts match the inside of the implant. On the femur side, the implant caps the end of the bone, and is called the femoral component. On the tibial side, the implant matches the femoral component so that this can hinge, pivot and glide for create smooth motion of the joint. It is important to understand that while many implants aim to mimic or improve the motion of the native (your original) joint, nothing will feel exactly like the normal joint. 

The tibial component (bottom part of the total joint) sits on top of the flat bone cut. Then, a polyethylene insert (sterilely processed plastic) which is manufactured to click precisely in place, is set onto the tibial component. The bearing surface of the joint is femoral component articulating with the tibial insert, which sits on top of the metal tibial component. 

Most commonly the patella is resurfaced, meaning that the back of the knee cap where there is cartilage is cut off in a flat cut. Then, a plastic patellar component, sometimes called a “button” is either cemented or pressed in place (if it has a metal backing). Sometimes, if the patella is too thin, it will be denervated and left alone. 

Sometimes cement is necessary for best fixation of the implant to the bone. This can be on the femoral side, the tibial side, behind the patella or any combination of the above depending on your bone quality, the implants utilized, the surgical method, and/or surgeon preference. 

Knee replacement implants come from different manufacturers, and have different designs similar to makes and models of cars. Although knee replacement surgery is one of the most common elective procedures performed, it is not a one size fits all surgery. Therefore, different patients will require different “makes and models” of their implants depending on factors such as their anatomy, bone strength, and metal sensitivity. Your surgeon will pick the implant(s) based off of these considerations, and preference for implant system(s). 

Robotic Assisted Surgery

Your surgeon may use a robot to assist with parts of the surgery. For knee replacement surgery, the robot is used for precise bone resection on the tibial and femoral sides.The use of a robot requires advanced imaging such as a CT scan done at least two weeks prior to the scheduled surgery. This allows the surgeon to create a personalized plan for your surgery and template the position of your implants based on your own anatomy before you even go to the operating room! You can think of the robot as a stable “extra arm” that the surgeon uses to make the surgery easier, and more accurate. Using the robot can also decrease the number of x rays needed to ensure precise placement of components. 

Minimally Invasive Surgery

Although minimally invasive joint replacement surgery sounds like less surgery, it is actually the same amount of surgery through a smaller incision. For knee replacement surgery, this is typically a subvastus (quadriceps sparing) approach which has a proposed benefit of decreased pain early after surgery. This is not always an appropriate option for everyone as the primary objective is to perform an effective surgery safely and efficiently. Although there are benefits to minimally invasive surgeries such as smaller scars and possibly some muscle sparing, these things are not as important as making sure the joint replacement goes in correctly. The biggest obstacle to a minimally invasive approach is body size, weight and habitus. If minimally invasive surgery does not work for your body type, the surgeon will choose the safest incision for your body to ensure a successful joint replacement surgery. 

Preparing for Surgery

Prior to surgery, the team abides by the following recommendations:

  • Medical Assessment: your PCP will evaluate you to risk assess and stratify you for elective surgery. This may include a recommendation to see other specialty health care providers including but not limited to a cardiologist, pulmonologist, etc to ensure that it is safe for you to have hip replacement surgery.
  • Pre-Admission Testing will also call and evaluate you prior to surgery. They may require additional testing or consultation with other physicians to ensure that you are healthy enough to have surgery. Joint replacement surgery is considered MAJOR SURGERY, and so blood loss, nerve injury, loss of limb and life are all potential though minimal risks of surgery. Therefore it is important to make sure these risks are mitigated as much as possible to ensure the safest way(s) to proceed with surgery. 
  • Watch the total joint arthroplasty class video or attend a total joint arthroplasty class: This is a combination of nursing and therapy care objectives to make it easier to understand how to live with a joint replacement directly after and for the first few months after surgery. This will include how to act and “not act” or the “do’s and don’ts” to make sure you avoid complications such as hip fracture and dislocation following surgery. 

 If you have had a steroid injection into your hip or knee joint in the last 3 months, you will have to wait until at least 3 months following the injection for surgery. Steroid injections within a 3 month period prior to joint replacement surgery puts you at higher risk for prosthetic joint infection. 

  • Shower with the provided surgical scrub provided in the preoperative appointment. 
  • No active dental caries: Active dental disease represents low grade focal infections which puts you at risk of having a joint infection. If you have cavities or severe gum disease, you will have to see a dentist to get this treated prior to joint replacement surgery. If you have active dental disease, you will have to wait after dental treatment for 6-8 weeks to decrease the risk of infection. 
  • Laboratory panel: You will have to have a blood draw within 1 month of surgery to assess for biological markers such as Hba1c, albumin, creatinine etc to determine your risks in undergoing surgery. Depending on these tests, you may have to delay surgery until these lab values are optimized. 
  • Maintaining a balanced diet (including calcium and Vit D).
  • Cessation of nicotine and marijuana use (if applicable) You will be tested for nicotine use prior to surgery, and if above a risk assessed threshold, surgery will be delayed until your lab tests are within acceptable limits. 
  • Temporary cessation of food supplements that may affect coagulation process or bleeding. 
  • Temporary cessation of Warfarin or other anticoagulants five days prior to surgery, in consultation with your prescribing physician.
  • Temporary cessation of immunomodulator or immunosuppressive medications to decrease the risk of infection and improve wound healing. See linked chart if you are on these medications. You may have to consult with your prescribing physician as well to determine if this is safe to do. 
  • Maintain cardiovascular fitness and strength as able prior to surgery. I recommend isometric exercises as this does not require motion of the joint as well as non/low weight bearing activities such as cycling, modified yoga/pilates, and swimming. 
  • Identifying a trusted person to help take care of you after your hospital discharge and assist in the first 7-10 days after surgery when energy level is low and mobilization is challenging or unsafe. 
  • Acquiring a walker (You will need to use the walker at all times for the first 2-6 weeks following surgery).
  • The hospital—BCH—will call to inform you of the time you should arrive at the hospital on the day of your surgery, and the time to begin fasting.

Dr. Lee adheres to these nationally and association recommended clinical practice guidelines recommended by the American Association of Hip and Knee Surgeons (AAHKS):

For patients taking immunosuppressive medication, please consult the following guidelines for timing of cessation prior to surgery.

Post-Operative Instructions
& Rehab Protocols

At discharge you will receive a post op folder with instructions on how to care for your dressings and when you may bath or shower. We ask that you do not remove your dressings unless they are saturated or leaking. If you are unsure, please review our instructional videos and call if needed. The post op folder will also include your medication instructions, a Persons With Disabilities parking privileges application and your hip arthroscopy photos. There is a pain/medication tracking sheet you will be asked to fill out and bring to the first post op appointment. A hip preservation team contact list will also be provided; use this to reach out with urgent matters.

"Dr. Mei-Dan did PAO operations on both of my hips when I was in high school. Thanks to him and his team, I've been able to come back from my injuries to compete in college soccer. Thank you to Dr. Mei-Dan for bringing me this far!"
– Evan Toth (PAO)