Knee Replacement

Whether you have a total or partial knee replacement, the same steps have to be performed during surgery:

1. After exposing the knee joint, usually with an 8-10 inch vertical incision in the front of the knee, the irregular, arthritic ends of the femur and tibia, along with some underlying bone, are cut and removed. These cuts are made in a way to keep the mechanical axis of the knee properly aligned.
2. Next, the ends of the bones are resurfaced with metal components. For this reason, although "total knee replacement" has been the term used for several decades, "knee resurfacing" would probably be a more accurate description since it is usually half an inch or less that is actually removed from the ends of the bones and replaced. It is not unlike a dental procedure in which a bad tooth is capped.
3. A polyethylene (plastic) spacer is then inserted between the two metal components in most knee designs.
4. The undersurface of the patella may or may not be resurfaced with a small plastic button. Most surgeons will decide at the time of surgery whether it is necessary.
5. The surgeon checks the biomechanics of the knee to ensure that it moves in as natural a way as possible.  
6. Next, the artificial parts are typically cemented into place. Antibiotics may be mixed into the cement if there is concern about infection.
7. The incision is then closed in multiple layers and a sterile dressing is applied. There are several ways to close the skin, ranging from staples to traditional sutures, to absorbable sutures with special surgical glue.

Our surgeons perform some surgeries using the OMNIlife iBlock computer navigation system. This system generates a 3D bone-morphing model of the patient’s anatomy and allows our surgeons to fit and align the knee before performing any bone resections. This ensures ideal leg alignment and desired outcome for more complex knee replacements.

There are many types of artificial knee joints. Your surgeon will choose the most appropriate one for you, depending on your age, weight, activity level, and overall health. Nearly all of them consist of two or three components.

The new piece for the end of your femur is made of highly polished metal. The tibial component, for the top of your leg, is made of metal and plastic. The patellar part is made of plastic and fits inside of your kneecap. The artificial pieces may or may not be cemented in place. The artificial joint will allow you to perform most of the pain-free movements that you used to be able to do. Most patients can expect to be in the hospital for 2 to 4 days after a total knee replacement and 1 to 3 days for a partial knee replacement. Learn what to expect the day of surgery and after surgery.

There are three compartments within the knee joint. Arthritis can occur in all three compartments, or it may only affect one or two compartments. If you experience arthritis in two or three knee compartments, you would benefit from a total knee replacement.

Partial Knee Replacement

If arthritis is limited to only one compartment, your surgeon may recommend a partial knee replacement, also known as unicompartmental knee replacement, which replaces one side of the knee only. During the surgery, only the damaged bone and tissue is removed and replaced with metal and plastic parts. The rest of the healthy tissue and bone is left alone. This is a less invasive procedure and typically has a quicker recovery, with the advantage of retaining more "factory original" parts.

Only certain patients are candidates for a partial knee replacement. It will only help the portion of the knee it replaces, and if both sides of the knee joint are worn out, it is often better to consider a total knee replacement. Some patients also have significant deformity or angulation, making it difficult or impossible to correct alignment and biomechanics without a total knee replacement.

Minimally Invasive Knee Replacement

Like traditional total knee replacement surgery, minimally invasive knee replacement involves removing the damaged portion of the knee and replacing it with artificial implants. However, minimally invasive knee arthroplasty uses smaller incisions than traditional surgery – typically only 3 to 6 inches – and a less invasive technique for opening the knee.

Instead of cutting through the quadriceps tendon and muscles to access the joint, this technique spares these tissues. Because the techniques used to expose the joint involve less disruption to the tendon and muscles surrounding the knee, patients usually experience less pain, a shorter hospital stay, and a faster recovery.

At Orthopaedics New England, we use a minimally invasive approach whenever possible. Not all knee replacement patients are good candidates, however. In general, those who are younger, thinner, healthier, and more motivated to participate in the rehabilitation process are the ideal candidates for minimally invasive knee replacement.

Knee Osteotomy

An osteotomy involves cutting the bone and realigning it to heal in a different position or angle. One particular application that is still used for early knee arthritis is a high tibial osteotomy, which involves cutting the upper end of the tibia and re-aligning it in such a way as to take weight off of the worn out side and to increase weight bearing on the "good" side of the knee. This changes the angle of the leg.

Therefore, to be considered a candidate for the surgery, most patients need to have severe arthritis in only one side of the knee with preservation of the joint on the other side. It is most often considered for a young patient with heavy physical demands, such as a heavy laborer, who traditionally has been a difficult-to-treat candidate for replacement surgery because of the demands placed upon the knee.

For most patients, a partial or total knee replacement is the ideal treatment for advanced arthritis, but for certain patients with specific needs, an osteotomy may be the better option.

There is a wide variation in how soon patients return to work. It primarily depends on what you do and also on your physical condition before surgery. Some patients return to desk jobs within several weeks. Others who have very physical jobs, such as laborers, may need to take 10 to 12 weeks until they are able to meet the demands of their job.

Essentially, we recommend that everyone returns to work when they can function safely and with reasonable comfort.

Most patients are able to drive within a week or two after surgery.

Most patients are able to resume sexual activity in a few weeks, when they feel up to it.

While there are typically no range of motion limitations for a knee replacement, in general it is best to avoid high impact activities such as running or contact sports after knee replacement, as this can decrease the life of the replacement and increase the likelihood of early loosening, possibly necessitating revision surgery.

Low impact activities such as walking, golf, cycling, swimming, hiking, or ballroom dancing are well tolerated by most joint replacements. Most joint replacements will last for many years with proper care and low impact activities.

If you have questions about activity or range of motion limitations after surgery, ask your surgeon.

New guidelines from the American Dental Association (ADA) and the American Academy of Orthopaedic Surgeons (AAOS) suggest that the risks of antibiotic use outweigh the benefits for the majority of patients. Most patients undergoing dental procedures do not require preventative antibiotics for their joint replacements.

There are some exceptions and patients with certain circumstances may benefit from antibiotic use after discussion with their dentist.

The length of time you can expect your knee replacement to last is highly variable. There are many factors that contribute to the longevity of the implants used, including the activities you pursue, your weight and age, and the type of bearing material used.

Impact activities (running, basketball, and other sports) will increase the likelihood of components loosening from the bone over time.

Patient weight has a significant influence over how long the replacements will last. Heavier patients place a larger load on the implants, but conversely, they often are less active (e.g., take fewer steps in a year).

While younger patients typically wear out replacements more quickly than older patients, implants have evolved to the point that younger patients can expect many years of use before requiring revision surgery.

The type of bearing material used also factors into longevity. There is some evidence that hybrid materials (zirconium oxide on plastic) will last longer. If part of the knee replacement does wear out, it often is only the plastic liner. In this case, most implant designs allow for a relatively quick procedure in which just the liner is replaced.