Knee Replacement

Knee replacement is one of the most common orthopaedic surgeries performed in the United States, and is only increasing due to the rise of patients being diagnosed with knee arthritis, and the improvement in the implant design, function, and longevity.  The goal of knee replacement is to improve patients quality of life, alleviate pain, and improve function. Knee replacement is used to alleviate symptoms in patients with knee osteoarthritis, rheumatoid arthritis, osteonecrosis, and post-traumatic arthritis.

Dr. Mosher is one of the top knee replacement surgeons in north Alabama, and performs both traditional total knee replacement and partial knee replacement, depending on the patient’s goals and level of degenerative changes. He also uses the traditional medial parapatellar approach and quad-sparing approaches to the knee.

The ultimate goal of knee replacement is getting patients to what they want to do without pain, so we will slowly release restrictions on patients, and will allow them to get back to running, cycling, rowing, playing competitive sports, heavy labor, and more if they desire. However, our goal is for ALL patients to be walking and climbing stairs withing hours of surgery. This early mobilization allows for rapid recovery and early discharge, which improves outcomes, patient satisfaction, and patient safety.

All patients will also be given a “multimodal” pain control regimen to control pain, while limiting the amount of harsh, narcotic pain medications to minimize medication-related complications and dependency.

We also may use robotic assistance or computer navigation during surgery to ensure that component placement is appropriate in an effort to boost patient satisfaction. While this technology continues to advance, it remains in its infancy. So, this is something that we will continue to monitor over coming years to improve patient outcomes. However, if patient’s desire robotic assistance, we are more than happy to perform these surgeries with a robot.

AAHKS link to videos of both a partial and total knee replacement (Link)

Common Questions

  • We use both cemented and cementless components. For partial knees, only cemented components are currently in use. For total knees, cementles components have shown lower revision rates in men of all ages, and possibly women under 65. For women over 65, we will likely use cement fixation. However, we always have both options available, and will be able to make an intraoperative determination based on your bone quality in surgery.

  • We will plan to selectively resurface the patella in a total knee arthroplasty depending on the cartilage on the patella and it’s appearance. However, if you have a partial knee performed, we will not resurface the patella.

  • This is a personal decision. In isolated arthritis to one compartment of the knee, a partial knee replacement is a safer surgery with fewer complications and overall improved outcomes (range of motion, recovery, “natural feeling knee”). For all partial knees, we will examine the entire knee in surgery to ensure that you have no significant wear in the other compartments. If you have multiple compartments of wear, we will plan for a total knee replacement.  While partial knees have better outcomes in isolated single compartment arthritis, they also have a higher revision rate for progression of arthritis in other compartments. This is a tradeoff for a more normal feeling knee, and this is a personal decision.

    AAHKS article regarding partial vs total knee arthroplasty (Link)

  • We will have no restrictions after surgery. We will hold off on formal therapy for 3-7 days after surgery to allow for pain control and swelling control. However, you can work on knee range of motion as desired immediately after surgery, with full weight bearing, and no brace.

  • There is no specific approach that is better. We use both a quadriceps tendon sparing approach, which is less invasive, and a traditional medial parapatellar (quadriceps splitting) approach. There has been no early or late differences noted in the literature regarding outcomes or function. We determine which is more appropriate given body habitus, preoperative knee range of motion, volume of arthritis, and soft tissue mobility, in order to improve function while decreasing complications.

  • We will use implants from one of the 4 major manufacturers. Generally, the implants are made of cobalt chrome and polyethylene (plastic) with the polyethylene on metal articulation. Sometimes we may use an implant made of oxinium (a metal-ceramic combination), which leads to an oxinium on polyethylene articulation.

    AAHKS article detailing total knee arthroplasty implant options (Link)

  • The articulation is polyethylene (plastic) on cobalt chrome or oxinium.

  • Our goal is for you to perform every activity you desire after surgery. In reality, you will probably not be a great skier if you have never skied before, but our goal is for you to be able to do that if you desire. Everyday activities such as walking, bending, stooping, going up/down stairs, jogging, skiing, working out, cycling, etc. should not be an issue. Prior to taking up distance running, we would need a more detailed conversation in clinic.

  • Yes, hip pain can refer to the knee causing knee pain. This is why frequently we will check you hip range of motion when evaluating your knee and often get hip x-rays as well.

  • Knee replacement really does not affect limb length. Our goal is to restore a functional knee joint to your pre-arthritic state. Usually, the change in limb length would only be 2-3mm at most.

  • This can be due to a multitude of factors. However, if you need a revision, we will use your same surgical incision, and place a larger, more stabilizing component in place. However, the components and reason for revision greatly affect the magnitude of surgery being performed. As with most things, not all revisions are created equal. 

  • This is different following partial and total knees. For a total knee, the first 1-2 weeks are aimed at pain control. Then weeks 2-4 are geared towards improving range of motion. At weeks 4-6, the goal is strengthening. Lastly beyond week 6, the goal is to maximize your recovery and get you back to daily life. Frequently after a total knee, it takes 6 weeks to really turn the corner, and 10-12 weeks to get back to normal life. Following a partial knee, these times can be decreased by 40-50%.

  • This is a controversial topic. This is a much larger surgery with more risks. However, there is some benefit to only going through the recovery once. The ideal patient for this is a young, very healthy individual who is highly motivated. Older patients are not appropriate for this, given the physiologic burden of bilateral, simultaneous surgery. 

  • We have the ability to use both computer navigation and robotic assistance as needed. These have some benefits in patients with prior hardware, to avoid having to take out hardware and possibly a second surgery. However, largely these technologies only help with the bone cuts and for implant positioning, and have not been shown in any study not funded by industry to significantly improve outcomes or decrease revision rates. However, we have these technologies available, if patients request or we think it is best. Notably, there is a slightly increased risk of fracture from pins that must be placed into the femur to use robotic assistance and a small additional wound over the leg and thigh, but otherwise, these have minimal risk in their usage.

    AAHKS article regarding technology usage in total knee arthroplasty (Link)

  • The entire goal of having knee replacement surgery being performed is to improve your quality of life, and to be able to perform the activities that you desire. With that said, our goal is to impose no restrictions upon you. However, patients with knee replacements tend to have difficulty kneeling moving forward, and may have to implement the usage of knee pads. Also, patients who desire to return to long-distance running will require a more detailed discussion in clinic.  We will impose some restrictions on you for 3-4 months, but then remove essentially all restrictions for you at that point. The key will be to listen to your body and slowly increase your activities to your desired level.

  • We would prefer you hold off for ~5 days after surgery before working with PT in earnest. You can work with PT immediately after surgery, but we just request that you refrain from deep knee flexion and passive-assisted range of motion. The key in the first couple weeks of surgery is maximizing your knee extension and gently working on improving knee flexion to limit your knee swelling and pain, whether this be on your own or with PT.

  • Your range of motion after surgery depends on your range of motion prior to surgery. If you were stiff prior to surgery, you are at higher risk of being stiff after surgery. The implants also have some limitations on deep flexion, so getting beyond 120 degrees of flexion can be very challenging after total knee replacement. Partial knee replacement patients tend to also have better range of motion than total knee replacement patients. This is something to discuss in detail prior to surgery in clinic, if it is a concern for you.

  • For partial knee replacement, we will keep your ACL. However, for total knee replacement, we will remove your ACL as part of the surgery. The implant is made to work in place of your ACL. There is a specific implant in the market where you keep your ACL and have a total knee replacement, but  the outcomes have been no different with that implant than with the implant we more commonly use.

  • The most common complications are broke down into surgical and medical complications. The most common medical complications are: nausea/vomiting from medication intolerance, uncontrolled pain, constipation from narcotics, difficulty urinating, uncontrolled glucose levels after surgery, insomnia, and fatigue. The most common surgical complications are pain, stiffness, wound drainage, hypertrophic scarring, and infection.

  • There are many places on the internet to obtain information regarding knee replacement with differing levels of reliability in the information being given. The American Association of Hip and Knee Surgeons has a patient-specific website for common concerns regarding knee replacement (Link). We encourage you to use this as a foundation for further information beyond this website.

  • No, this is not necessary after a standard partial or total knee replacement. The data shows that these may improve early knee range of motion, but at 1 year there is no difference in range of motion between patients who have and have not used the device. So, “torturing” the patient for no benefit makes no sense.

Risks, Benefits, and Alternatives

Benefits: Our goal is to give you a stable, well-functioning knee. We want you to get back doing the things you enjoy.  The potential benefits of TKA include: pain relief, improved function, improvement of range of motion, improved stability and activity level, and increased ability to do activities as desired. 

Risks: There are risks associated with TKA. The risks and our mitigation of those are listed below. The cumulative risk of any one of these is about 3-5%.

Infection/wound healing complications: We use prophylactic antibiotics, antiseptic solutions, advanced wound healing devices, and maintain sterile technique. However, the risk of infection is never 0%. If an infection occurs, you will need another surgery, IV antibiotics, and oral antibiotics.

Fracture: This can uncommonly occur with the usage of cementless components and final implant placement. Wewill  obtain an X-ray after surgery to ensure this did not occur. 

Implant Loosening: We place your implants using a variety of cemented and cementless techniques. Neither option is perfect. Thus, these uncommonly can loosen down the line. We will monitor this throughout the healing process.

Neurovascular Injury: TKA requires exposure for component placement, placing the nerves and blood vessels at slight risk. The tibial and peroneal nerves are the most common affected. Tibial nerve injury can lead to numbness, while peroneal nerve injury leads to a foot drop, both of which often improve on their own. The popliteal vessels are also at risk. All structures are protected by retractors during the surgery. You will also have superficial lateral knee numbness from the incision.

Extensor Mechanism Injury: The extensor mechanism (patella tendon, patella, and quadriceps tendon) can be scarred into place and stiff. We place retractors and obtain appropriate exposure to mitigate this risk.

Stiffness/Instability: These can occur with any knee surgery. We will get you into aggressive therapy to mitigate these risks, and monitor your progress for early intervention if needed.

Dissatisfaction: In TKA, the goal is to improve your knee function, but it may never be “perfect,” leading to some dissatisfaction.  Our goal is to give you the best functioning knee possible.

Pain: Infrequently, patients can have issues with pain after surgery. These tend to resolve, and we work to mitigate this via appropriate component placement and respecting the soft tissues.

Altered Gait: It will take time for your body to accommodate the new surgery and implant, and it can take some time for your muscles to accommodate, leading to a limp. This should improve with time.

Venous Thromboembolism (VTE): This includes DVT and pulmonary embolism. This risk is elevated after TKA. We give at least 1 baby aspirin twice daily for 4 weeks to prevent this.

Medical Complications: These include: heart attack, stroke, pneumonia, UTI, VTE, kidney injury, bleeding, even death. However, these are present with any surgery, and not specific to revision THA. The more common “medical complications” we manage are nausea/vomiting, narcotic intolerance, drug interactions, urinary retention, pain, etc, which can usually be managed over the phone.

Alternatives: Continue nonoperative management. This is a continuation of your current management, including: anti-inflammatories, physical therapy, bracing, and injections. These may be helpful in a short-term situation, but are not a long-term solution.

Unique Differenes with Partial (Unicompartmental) Knee Replacement

Overall, the partial knee replacement tends to have a higher functional capacity after surgery, with a expedited recovery in comparison to the total knee replacement. However, since only the diseased area is being replaced, there can be progression of arthritis in the other compartments of the knee leading to futher surgery to address these changes—thus partial knee replacement will always have a higher revision rate than total knee replacement.