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total knee replacement

TOTAL KNEE REPLACEMENT

Total knee Replacement OVERVIEW

When the knee joint is damaged by arthritis or injury, simple daily activities, such as walking or climbing stairs can become difficult. A total knee replacement is really knee cartilage replacement with an artificial surface. The knee itself is not replaced. An artificial substitute for the cartilage is inserted onto the end of each of the bones. This is done with a metal alloy on the end of the femur and tibia, with a medical-quality plastic inserted between them. The cartilage on the under-surface of the kneecap may also be replaced with plastic. Replacement of the worn cartilage with a metal and plastic implant creates a new, smoother cushion and a joint with improved function. Although technically not a normal knee, a replaced knee provides relief from the arthritis and injury pain. Most patients experience a significant decrease in their pain with progressive improvement in range of motion after knee replacement. These improvements provide an increased quality of life with a return to activities without the daily burden of joint pain.

The initial step when considering knee replacement surgery is to meet with a qualified, experienced orthopedic surgeon to see if you are a candidate for total knee replacement surgery. Your surgeon will take your medical history, perform a physical examination, and X-ray your knee. Often even with significant pain, and if X-rays reveal advanced arthritis within the knee joint, initial treatment is almost always non-surgical options. Available treatment options prior to knee surgery may include weight loss if appropriate, an exercise program, medications, joint injections, or bracing. If there is no joint symptom improvements despite these measures, then you may be encouraged to consider surgery. Joint replacement is considered a major surgery, and the decision to move forward with surgery is not always straight forward and often involves a thoughtful conversation with yourself, your loved ones, and an experienced surgeon. The final decision rests with you and is typically based on the pain and disability from the arthritis influencing your quality of life and daily activities. Candidates for Total Knee Replacement surgery commonly report that their symptoms keep them from participating in activities that are important to them like walking, taking stairs, working, sleeping, etc.

basic knee anatomy

As the largest joint in your body, healthy knees are required to perform most basic daily activities. The knee is made up of the lower end of the thighbone (femur), the upper end of the shinbone (tibia), and the kneecap (patella). The surfaces of theses three bones that touch are covered with articular cartilage, a smooth surface that protects the bones and enables the joint to move easily. The menisci are located between the femur (thighbone) and tibia (shinbone). The menisci are C-shaped wedges that act as shock-absorbers to cushion the joint. Large ligaments hold the femur and tibia together and provide knee joint stability. The long thigh muscles give the knee strength and additional stability. All remaining surfaces of the knee joint are covered by a thin lining called the synovial membrane which releases a fluid that lubricates the cartilage and reduces friction within the knee. In a healthy knee joint, all of these components work in harmony to provide smooth, pain-free range of motion. Disease (most often Arthritis) or injury can disrupt this harmony, resulting in pain, lack of joint mobility, muscle weakness, and reduced function.
knee anatomy diagram
The most common cause of chronic knee pain and disability is arthritis. Although there are many types of arthritis, most knee pain is caused by just three types: osteoarthritis, rheumatoid arthritis, and post-traumatic arthritis.

Osteoarthritis. This is an age-related "wear and tear" type of arthritis. It usually occurs in people 50 years of age and older, but may occur in younger people, too. The cartilage that cushions the bones of the knee softens and wears away. The bones then rub against one another, causing knee pain and stiffness.
Rheumatoid arthritis. This is a disease in which the synovial membrane that surrounds the joint becomes inflamed and thickened. This chronic inflammation can damage the cartilage and eventually cause cartilage loss, pain, and stiffness. Rheumatoid arthritis is the most common form of a group of disorders termed "inflammatory arthritis."
Post-traumatic arthritis. This can follow a serious knee injury. Fractures of the bones surrounding the knee or tears of the knee ligaments may damage the articular cartilage over time, causing knee pain and limiting knee function.
knee osteoarthritis and rheumatoid arthritis diagram

description of total knee replacement

A knee replacement (also called knee arthroplasty) might be more accurately termed a knee "resurfacing" because only the surface of the bones are actually replaced.There are four basic steps to a knee replacement procedure.
1. Prepare the bone. The damaged cartilage surfaces at the ends of the femur and tibia are removed along with a small amount of underlying bone.
2. Position the metal implants. The removed cartilage and bone is replaced with metal components that recreate the surface of the joint. These metal parts may be cemented or "press-fit" into the bone.
3. Resurface the patella. The undersurface of the patella (kneecap) is cut and resurfaced with a plastic button. Some surgeons do not resurface the patella, depending upon the case.
4. Insert a spacer. A medical-grade plastic spacer is inserted between the metal components to create a smooth gliding surface.

Anesthesia

You will most likely be admitted to the hospital on the day of your surgery. After admission, you will be evaluated by a member of the anesthesia team. The most common types of anesthesia are general anesthesia (you are put to sleep) or spinal, epidural, or regional nerve block anesthesia (you are awake but your body is numb from the waist down). The anesthesia team, with your input, will determine which type of anesthesia will be best for you.

While general anesthesia is a safe option, both hip and knee replacements can be performed under regional anesthesia. Choices for regional anesthesia include spinal anesthesia, epidural anesthesia, or one of a variety of peripheral nerve blocks. Many surgeons and anesthesiologists prefer regional anesthesia because data shows it can reduce complications and improve your recovery experience with less pain, less nausea and less narcotic medicine required. Recently, peripheral nerve blocks have become more popular as an adjunct for pain control. For total knee replacement this can include an adductor canal block, which allows pain control without causing weakness of your muscles. You should have a discussion regarding anesthesia and post-operative pain management with your surgeon and anesthesia team prior to your surgery.

Are all knee replacement implants the same?

The orthopedic implant industry has developed a number of innovative technologies in an effort to improve the outcomes of total joint replacement surgery. In recent years, these technologies have been marketed directly to patients, which has increased the awareness as well as confusion on what these different designs mean. The most important message is that while a certain manufacturer may claim that their design is better, almost all of the available registry data (large collections of data that track total joint surgery outcomes) show that there is no clear advantage to any of these designs when it comes to improving outcomes. Here are specific implant design terms your surgeon may discuss:

Gender specific Joint Replacement Implant: This refers to a modified implant design that accounts for average anatomic differences between men’s and women’s knees. Most manufacturers have incorporated similar modifications in their newer designs, which allow for more sizing options so that the prosthesis can be more accurately fit to the patient’s native anatomy and recreate the natural function of the knee.

Rotating platform Joint Replacement Implant: This refers to a plastic bearing that independently rotates on a metal tray on which it is seated. More often, the plastic bearing locks into the metal tray – referred to as a “fixed bearing.” Some theoretical advantages to the rotating platform concept when it was initially designed was that it could reduce the wear of the plastic bearing, reduce the rate of loosening of the metal parts, and better replicate how a patient’s knee works (kinematics). Most current data shows that after five to ten years in use, there does not appear to be any difference between rotating platform and fixed bearing designs in any of these outcomes.

total knee replacement surgical procedure

Video Source: American Academy of Orthopaedic Surgeons OrthoInfo, https://orthoinfo.aaos.org/ Traditional Total Knee Replacement involves a 7-8” incision over the knee, a hospital stay of 1-3 days, and a recovery period (during which the patient walks with a walker or cane) typically lasting from one to three months. The large majority of patients report substantial or complete relief of their arthritic symptoms once they have recovered from a total knee replacement. This is highly dependent upon your condition before surgery, your age, and medical problems which can influence your rehabilitation. A safe discharge plan will be arranged for you by the orthopedic team.

Knee replacement recovery

The success of your surgery will depend in large measure on how well you follow your orthopedic surgeon's instructions regarding home care during the first few weeks after surgery. You may have stitches or staples running along your wound or a suture beneath your skin. The stitches or staples will be removed approximately 2 weeks after surgery. Avoid getting the wound wet until it has thoroughly sealed and dried. You may continue to bandage the wound to prevent irritation from clothing or support stockings. Some loss of appetite is common for several weeks after surgery. A balanced diet, sometimes with an iron supplement, is important to promote proper tissue healing and restore muscle strength. Be sure to drink plenty of fluids. The majority of people who undergo total joint replacement are able to participate in a majority of their daily activities within six weeks. By three months, most people have regained much the endurance and strength lost around the time of surgery, and can participate in daily activities without restriction. While daily activities have resumed, it is important to avoid high impact activities to give you the best long-term outcome with your hip.

physical therapy and recovery following knee replacement

Initially, you will receive some physical therapy while in the hospital. Depending on your preoperative conditioning and support, you may or may not need additional therapy as an outpatient. Much of the therapy after knee replacement is walking with general stretching and thigh muscle strengthening, which you can do on your own without the assistance of a physical therapist. To assure proper recovery and prevent dislocation of the prosthesis, you may be asked to take special precautions when sitting, bending, or sleeping — usually for the first 6 weeks after surgery. These precautions will vary from patient to patient, depending on the surgical procedure your surgeon used to perform your knee replacement. Prior to discharge from the hospital, your surgeon and physical therapist will provide you with any specific precautions you should follow.

You may feel some numbness in the skin around your incision. You also may feel some stiffness, particularly with excessive bending. These differences often diminish with time, and most patients find these are minor compared with the pain and limited function they experienced prior to surgery. Your surgeon will carefully discuss other post-surgical complications to watch for during your joint replacement recovery.

Before surgery, you should prepare your home for your return from the Hospital. Think safety by doing the following:
• Picking-up throw rugs and tack down loose carpeting.
• Remove electrical cords and other obstructions from walkways.
• Install nightlights in bathrooms, bedrooms and hallways.
• Complete routine house and yard work.
• Prepare a few meals before your surgery.
• Place frequently used items within easy reach.
• Arrange to have someone collect your mail and take care of pets and loved ones, if necessary.

follow-up and precautions following knee replacement

It is important to follow up with your surgeon after your joint replacement. In most cases, joint replacements last for many years. You need to meet with your treating doctor after surgery to ensure that your replacement is continuing to function well. In some cases, the replaced parts can start to wear out or loosen.The frequency of required follow up visits is dependent on many factors including the age of the patient, the demand levels placed on the joint, and the type of replacement. Your physician will consider all these factors and tailor a follow-up schedule to meet your needs.In general seeing your surgeon every three to five years is recommended.
Source: American Academy of Orthopaedic Surgeons, https://orthoinfo.aaos.org/; American Association of Hip and Knee Surgeons, https://hipknee.aahks.org/total-hip-replacement/
Cory Calendine, MD is an Orthopedic Surgeon and founding partner of the Bone and Joint Institute of Tennessee at Williamson County Hospital in Franklin, TN. Dr. Calendine is an expert in Joint Replacement, specializing in Hip and Knee Surgery. From diagnosis through treatment, the Orthopedic Surgical experts at the Bone and Joint Institute use the latest techniques and technology to improve care for people with musculoskeletal problems. For more information, please contact our office or schedule your appointment today.
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