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partial knee replacement


partial knee Replacement OVERVIEW

Knee replacement is a surgical procedure that decreases pain and improves the quality of life in many patients with severe arthritis of the knees. Typically patients undergo this surgery after non-operative treatments (such as activity modification medications knee injections or walking with a cane) have failed to provide relief of arthritic symptoms. Surgeons have performed knee replacements for over three decades generally with excellent results; most reports have ten-year “success rates” in excess of 90 percent. Broadly speaking there are two types of knee replacements: total knee replacements  and Partial (or unicompartmental) knee replacements.

While it may seem appealing to have half of a surgery compared to a full surgery, it is important to understand the differences between a unicompartmental (partial) and a total knee replacement surgery. Each type of knee replacement surgery is unique and has its own outcomes after surgery.The knee is composed of three compartments: the inside (medial), outside (lateral) and underneath the knee cap (patellofemoral/anterior). Each of these compartments can be replaced individually in partial knee replacement surgery, or all three can be replaced in total knee replacement surgery*. A partial knee replacement is technically one-third of the surgery of a total knee replacement. If you have a partial knee replacement, you will find improvement in the function of your knee, but there are some long-term factors to consider.

Partial Knee Replacement is an alternative to total knee replacement for patients whose disease is limited to just one area of the knee.Because a partial knee replacement is done through a smaller incision, patients usually spend less time in the hospital and return to normal activities sooner than total knee replacement patients.There are a range of treatments for knee osteoarthritis and your doctor will discuss with you the options that will best relieve your individual osteoarthritis symptoms.

Because a partial knee replacement is less surgery, it has often been reported to have an easier, quicker, more complete recovery and greater satisfaction than a full knee replacement.2  Complications during surgery like blood loss, transfusion and blood clots tend to be less with a partial replacement;3 however, long-term studies show the lifespan of partial knee replacement components is not as long as the lifespan of components used in a total knee replacement.4,5Because partial knee replacement retains most of your knee tissue, you are still susceptible to meniscal tears and progression of arthritis in the rest of the knee. When a partial knee replacement fails, it can be converted to a full knee replacement with an excellent degree of success. The surgery and recovery may be more involved, but the overall outcomes are highly successful.6

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. Your knee can be divided into three major compartments: Medial compartment (the inside part of the knee), Lateral compartment (the outside part), and Patellofemoral compartment (the front of the knee between the kneecap and thighbone).

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.
basic knee anatomy intra-articular 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.
osteoarthritis and rheumatoid arthritis diagram

description of partial 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.

Advantages and disadvantages of Partial vs. Total Knee replacement

Multiple studies show that a majority of patients who are appropriate candidates for the procedure have good results with unicompartmental knee replacement.The advantages of partial knee replacement over total knee replacement include:Quicker recoveryLess pain after surgeryLess blood lossAlso, because the bone, cartilage, and ligaments in the healthy parts of the knee are kept, many patients report that a unicompartmental knee replacement feels more natural than a total knee replacement. A unicompartmental knee may also bend better.

The disadvantages of partial knee replacement compared with total knee replacement include:Slightly less predictable pain reliefPotential need for more surgery. For example, a total knee replacement may be necessary in the future if arthritis develops in the parts of the knee that have not been replaced.

Both partial and total knee replacements can be highly successfully for patients who are good candidates. It is important to discuss the risks and benefits of each type of surgery with your surgeon so that your expectations are in line with the procedure you elect to have. Remember that both of these procedures are replacements, and you should follow the activity restrictions your surgeon provides you. Neither procedure is designed to hold up to the rigors of high-impact sports. If you take care of your total or partial knee replacement it will provide you with the greatest longevity possible.

partial knee replacement surgical procedure

Video Source:  “Minimally-invasive” partial knee replacement (or "mini knee") is a surgical technique that allows a partial knee replacement to be inserted through a small (3-3.5”) incision (see figure 5) with minimal damage to the muscles and tendons around the knee.The small size of the incision and the less-invasive nature of the surgical approach allow patients to recover from the “mini knee” operation much more quickly.

Partial knee replacement surgery

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 knee.

With Partial Knee Replacement surgery hospital stays are shorter--down to 1 or 2 days for most patients--and the recovery period is much faster. Patients lose less blood experience substantially less pain than traditional knee replacement and often walk unassisted (no cane or walker) within a week or two of the operation (see movie 1). Even many patients who have both knees done at once with this newer technique are able to walk without the assistance of a walker or cane fairly quickly.

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,; American Association of Hip and Knee Surgeons,
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.