Total Knee Replacement
Written by: Dr. Frederick Buechel, Jr.
What is a Total Knee Replacement?
A total knee replacement is a surgical procedure that places new artificial surfaces on the ends of the bones of the knee joint where the original cartilage surface is damaged or worn away. The knee joint has 3 compartments, the medial on the inside, the lateral on the outside, and patellofemoral compartments which is the kneecap and the front of the thigh bone. A total knee replacement replaces the surface of all 3 compartments of the knee joint with metal and plastic parts called “implants”.
The metal parts are usually cobalt chrome and/or titanium, and the plastic part, called the “insert” or “bearing”, is ultra-high molecular weight polyethylene. The parts are usually attached to the bone using a bone cement, and sometimes they can be attached without cement which is called cementless. Cementless implants have a special surface that allows the bone to grow into the metal biologically attaching the implant.
What are the main indications that someone may require total knee replacement surgery?
The main indication for requiring a total knee replacement is when a person has global knee pain with weight-bearing activity not just in one compartment, and their quality of life is reduced due to the loss or damage of their knee cartilage. They should also have tried conservative treatments first, and no longer are responding to non-surgical treatment. Osteoarthritis is the most common diagnosis for total knee replacement. Rheumatoid arthritis and other inflammatory arthritis forms such as gout and psoriatic arthritis are other indications for total knee replacement. These inflammatory arthritis conditions are not good indications for partial knee replacement.
Osteonecrosis is also a good indication for total knee replacement and occurs when there is loss of blood supply to the bone and the bone in certain areas dies causing pain and collapse of the overlying cartilage surfaces. Post-Traumatic arthritis is another indication and occurs when the joint surface cartilage is damaged due to an injury, and the cartilage breaks down causing pain and inflammation.
Patients with severe angular and fixed deformities are better treated with total knee replacement over partial knee replacement, in most cases.
To determine if you are a good candidate for total knee replacement, you need to see a surgeon who is experienced with total and partial knee replacement, so they can help you make the right decision.
During your visit you should expect to provide a comprehensive medical and knee history, have a physical examination, have proper x-rays taken and reviewed with you, and if necessary, an MRI of the knee may be ordered if there is further need to confirm the condition of the knee.
What are symptoms of someone who needs total knee replacement surgery?
- Pain that is located all around the knee, not on just one side or under the kneecap alone.
- Pain in the knee when walking
- Pain getting up from a seated position
- Pain going up and/or down stairs.
- Dull or aching pain
- Stiffness in the knee
- Swelling of the knee joint.
- Loss of motion in the knee.
- Decreased walk distance
- Reduction in activities of daily living
- Reduction in sports and exercise activities.
- No relief anymore from NSAIDs, injections, ice, physical therapy, or other non-surgical treatments.
How do I know I need total knee replacement surgery instead of a partial knee replacement?
The way to differentiate between needing a partial and total knee replacement depends on several factors. These include the location of the pain, the x-ray or advanced imaging findings, and the diagnosis of the knee condition. If the pain is located throughout the entire knee, then these patients most likely require total knee replacement.
If the pain is located in just one of the three compartments, then these patients may only require partial knee replacement. If the x-rays show the joint space is decreased or completely lost in just one compartment, this is a possible partial knee patient. If the x-rays show the joint space is decreased or completely lost in the medial and lateral compartments along with the patellofemoral compartment, this is a total knee patient.
If the patient has inflammatory arthritis such as rheumatoid arthritis, then total knee replacement is needed. If it is non-inflammatory arthritis such as osteoarthritis, then you may have the option of partial vs. total knee replacement depending on the other factors. Bone spurs are also common findings on x-rays with patients with painful arthritis. These spurs can sometimes have significant meaning and affect the decision of partial vs. total knee replacement. The large variation in patient’s clinical presentation is why it is important to have an experienced partial knee surgeon examine your knee and review the x-rays, when making a proper decision between partial and total knee replacement.
Is there a difference between total knee replacement and resurfacing?
There are several terms that are used interchangeably to describe knee replacement. The synonymous names include knee replacement, knee resurfacing and knee arthroplasty. The term resurfacing is sometimes more commonly associated with partial knee replacement, but it can be used for both total and partial.
What does the incision look like for a total knee replacement?
The incision should not be the main focus of a joint replacement surgery, but it is what the patient sees in the end, and a cosmetic incision is more desirable for everyone. This is why I prefer to do the entire closure myself, so I can control the quality of the closure and have the greatest impact on the appearance of the incision with my attention to detail. The incision length should be the smallest length the surgeon needs to properly see the bone edges, get enough exposure to balance the ligaments properly, and get the implants in without causing too much stretch or injury to the skin.
Very small total knee skin incisions have led to a variety of problems including increased infection rates, skin necrosis, delayed wound healing, retained cement, poor ligament balance all which are more important than an extra inch or two of skin incision length. My incisions are generally 1.5 inches above the patella down to the tibial tubercle. With my technique and the special sutures I use under the skin, the skin adhesive used to seal the incision, and the silicon dressings after the surgery, the resultant scar is usually a fine line about 3-6 months after surgery.
The larger the thickness of fatty tissue under the skin, the more difficult it is for the healing to be a fine line in the end. The incision area above the kneecap can leave a wider scar if there is a large amount of fat. Usually, the incision below the kneecap stays thin for patients that are skinny or have more fatty tissue.
Implant Design Options for Total Knee Replacement:
During total knee replacement operations surgeons have options on the types of implants that can be used based on the ligaments that are still functioning, the deformity of the knee, and the surgeon’s preference and familiarity with each system. The two main categories for implant designs based on the ligaments functioning are the Posterior Cruciate Retaining implants (PCR) and the Posterior Cruciate Sacrificing (PCS) implants.
Each of these implant designs have shown similar outcomes and longevity when installed properly and optimally. With any design, the critical factors for long term success and patient satisfaction require the surgeon to optimally cut the bone and balance the ligaments of the knee when installing the implants. The collateral ligaments on the sides of the knee joint (MCL & LCL) are assumed to be intact and functional in order to use these standard primary implants. If one or both collateral ligaments are damaged, severely stretched, or cut, a different type of implant is required that substitutes for the collateral ligaments.
Posterior Cruciate Retaining Implants
- Anatomically, the PCL comes off the back of the tibia and connects to the inside center end of the femur (thigh bone). The PCL stabilizes the shin bone (tibia) from moving posterior to the femur.
- Posterior Cruciate Retaining (PCR) total knee replacement means that during the preparation of the knee for the implants, the posterior cruciate ligament is maintained and not removed. With these implants and most total knee replacements, the ACL is removed.
- These implants are designed to leave room for the PCL, one of the 2 middle knee stabilizers. If balanced properly, PCL retention allows for some of the natural protections and movements afforded by this ligament to remain.
- This option takes more time to properly prepare and protect the PCL during the bone preparation steps and requires a detailed assessment of the implant balance and position to make sure the installation is correct.
- If PCL is not present, design features are implemented to substitute for its removal or loss.
Posterior Cruciate Sacrificing Implants
- If the PCL ligament is not present, or if the knee is too tight or too deformed requiring removal for proper ligament balancing and alignment, then a PCL sacrificing design implant is often used.
- These implants have a design feature that has a post in the middle of the plastic insert that contacts the femur implant and causes a “roll-back” of the femur on the tibia, simulating what the PCL does.
- This design also requires a different femur implant that has a larger central section that engages with the plastic post, and this requires more bone removal at the end of the femur.
- Some surgeons also prefer this implant design over the PCS design as a matter of training and philosophy.
Implant Fixation Options for Total Knee Replacement:
There are also two options on how to attach the implants to the bone. These options are ‘cemented’ and ‘cementless’. Both options when used properly have similar good fixation results when installed properly, but neither option is 100% failure resistant.
The cemented option is most commonly used, as there have been more implants designed and approved on the market for this type of attachment. Cemented implants are attached to the bone immediately at the time of surgery using a bonding agent that attaches to the backside of the implants and to the surface pores of the bone. The cement material is called polymethylmethacrylate. It is a powder and liquid that is mixed in the operating room that turns to a white liquid and hardens in a matter of minutes, after being applied to the implants and bones. Cement has been shown to last decades when properly used to attach implants to bone. However, there is always a chance of the cement debonding from the implants or the bone. Repetitive high-impact activities and heavy loading is a concern for loosening implants in cement.
Cementless implants have special coatings on their backsides that make contact with the bone surface allowing the bone to grow onto, or into the material. This is a biological fixation system that provides the opportunity for long-term attachment and avoidance of potential loosening events from cement fixation. Initially, these implants are attached with a press fit that “wedges” the implant into the bone tightly until the bone has enough time to grow onto the implant, over several months. These can be used on younger or older patients but require proper bone density and strength that is determined at the time of surgery. These implants attach to the bone best when the surface cuts of the bone are very precise, allowing optimal bone surface area to contact the implant surface. The Robotic-Arm Assisted bone preparation with the Mako™ Total Knee System and the Triathlon® Total Knee creates such precision bone cuts so these implants which are approved for cementless fixation can be optimized.
Is Robotic-Arm Assisted Total Knee Replacement considered a virtual knee surgery?
Mako™ Robotic Total knee replacement is not virtual surgery like the DaVinci Robotic Surgery System. Mako Robotic Total Knee Replacement uses a CAT scan to allow the surgeon to perform extremely accurate preoperative implant planning customized to the individual. Intraoperatively, the surgeon attaches communication arrays (reflectors) to the two bones that allows the surgeon to see the live knee motion and balance on a computer display, and make fine adjustments to the implants position, prior to preparing the bone with the Robotic-Arm’s cutting tool that the surgeon holds and controls. The Mako™ Robot is then controlled by the surgeon who holds the cutting tool on the end of the Robotic-Arm to remove the bone exactly where it was planned in the software, with reproducible precision of 1mm and 1 degree. The software can then be used to confirm the implants are installed properly in the bone and cement using tracking probes, to confirm the final position. The software also provides initial information to show the ligament balance of the knee before adjustment, after adjustment, and after installation of the implants.
What is the typical preparation needed for total knee replacement?
Patients that are considering undergoing total knee replacement can do several things to prepare for their surgery. Some are required, others are to optimize your outcome. All patients should have a medical checkup by their family physician or medical doctor to clear you for surgery and provide medical recommendations. If there are any special medical conditions you have, a specialist may be required to check you out and provide recommendations for your management before, and after your surgery. These specialists might be cardiologists if you have heart conditions, nephrologists if you have kidney conditions, hematologists if you have blood conditions, or other specialists that have helped you over the years for your particular situation. You should optimize your health prior to your surgery. Optimizing your health means:
- Eating well
- Getting enough protein
- Taking appropriate vitamin supplements and discontinuing those that can increase bleeding prior to surgery
- Getting appropriate sleep
- Exercise in preparation for your recovery therapy
- Perform daily quadriceps isometric exercises to prepare for after surgery
- Reducing alcohol intake (try to stop before surgery)
- Stop smoking (smoking increases complication)
- Prepare your home for your arrival after surgery
- Contact your insurance company to understand your benefits (each plan is different)
- Discuss your plans with work and prepare for time off
What is the expected pain with a total knee replacement?
Pain after total knee replacement can best be managed with what is called multimodal anesthesia and a comprehensive approach to swelling and pain control. Before surgery, if you are taking prescription pain medications you should try to eliminate them as best as possible, so that they can be more effective around the time of surgery.
If you have been taking prescription pain medicine for a long time, you may not get the relief you would if you had not been taking them prior to surgery. Anesthesia can make a big difference in immediate postoperative pain. The use of region blocks can eliminate most if not all of the pain for the first day. Spinal anesthesia is a great way to perform your surgery if this is an option for you. Regional blocks including Adductor Canal Blocks (ACB) and anesthetic Infiltration between the Popliteal Artery and Capsule of the Knee (IPACK) blocks are given by the anesthesiologist in the operating room after the spinal or general anesthesia is given. Peri-articular blocks with local anesthesia are injected into the surgical site by the surgeon at the end of the knee replacement procedure. All of these blocks in combination can significantly reduce your postoperative pain.
After surgery, there are several ways to control pain. One important pain controlling factor is to keep the swelling down because swelling activates pressure pain receptors that cause pain until the swelling goes down. Swelling reduction is optimized by using compression, cold therapy, elevation of the leg to heart level or above, and isometric quadriceps exercises. Medications that help reduce pain include NSAIDs, Acetaminophen, oral and intravenous narcotics. Using the least amount of pain medication that controls your pain is best. Each person experiences pain differently, which is why we use so many different modalities to help minimize this pain and individualize medications according to each patient’s needs.
How do most patients review their total knee replacement?
Once the healing process and rehabilitation is completed, most patients review their knee replacement surgery as life changing. Most people will say the surgery has given them their lives back. Patients often describe how they are able to do things they haven’t been able to do in years. However, if you review patient satisfaction outcomes surveys, 20-30% of patients are not satisfied with their results. Usually, this is due to ligament imbalance during implant installation. This is why precision installation of knee implant and optimizing ligament balance around these implants is so important for patients to have the great outcome they hope for. This is why Robotic-Arm Assisted Total Knee replacement is such a great advancement in helping surgeons do a better job installing knee replacements.
What is the follow-up care like for a total knee replacement surgery?
The follow-up care for total knee replacement starts in the hospital. Patients are managed by the medical and surgical teams in the hospital during their stay. Physical therapists are a key part of getting patients up and mobile after surgery. They participate in the care at the hospital and for several months after surgery in rehabilitation facilities, during home physical therapy, and in outpatient therapy programs. Early in the follow-up care for total knee replacement patients the focus is on achieving good wound healing and avoidance of infection. This can be optimized in many ways. Optimal surgical wound closure and gentle handling of the skin and tissues during the surgery is critical. The use of skin adhesives can seal the incision after the deep and superficial suturing is complete. These skin adhesives can keep out bacteria, allow for showering right after surgery, and avoid having painful staples removed that also leave unpleasant scaring. Good nutrition & protein intake, supplementation with Vitamin C, and avoidance of smoking are important in wound healing optimization.
Swelling management is a critical part of proper care following total knee replacement. Keeping the leg elevated when not walking or exercising after surgery for the first 2-3 weeks significantly reduces potential leg swelling. The use of cold therapy devices helps with wound healing by reducing the pressure on the incision which allows the tissues to knit together faster and better. The use of compression sleeves can also help with swelling reduction as long as they are comfortable and are checked by the patient regularly so as not to slide down on the leg, which can cause local constriction an tissue injury.
Office follow-up visits with the surgeon early on are for wound evaluation, swelling evaluation, range of motion checks, pain control discussions and to listen to and help with any issues that have arisen since the surgery. As the weeks and months pass, follow-up becomes more focused on function, strength and motion. Implant evaluations are done at follow-up intervals by examining the patients range of motion, stability and by obtaining x-rays to evaluate the status of the bone implant interfaces, implant insert thickness and alignment. As the years go by, interval examinations are done to evaluate for implant insert plastic wear and metal bone attachment to ensure the implants are stable and prepare for future intervention if the parts over time begin to wear down or loosen.