What is Total Knee Replacement?
Total knee replacements are one of the most successful procedures in all of medicine. According to the Agency for Healthcare Research and Quality, more than 790,000 knee replacements are performed each year in the United States. What exactly is a Total Knee Replacement? What does the surgeon put in my body during knee replacement? Is there a lot of leg bone removed in Total Knee Replacement?
In this week's vlog, Dr. Calendine offers a practical, patient-centered explanation of Total Knee Replacement surgery. Dr. Calendine answers the questions above, and more, as he carefully walks you through the (4) main components of 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.
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Common Causes of Knee Pain
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.
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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.
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.
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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.