Minimally-Invasive Surgery (MIS) Quadriceps-Sparing Total Knee Replacement: New Quad Sparing Technique May Provide Faster Recovery for Patients with Arthritis of the Knee.

Edited By: Seth S. Leopold, M.D.
Last updated Tuesday, April 15, 2008

Figure 1 - The incision used for minimally-invasive quadriceps-sparing total knee replacement is much smaller than the one used for traditional knee replacement, and in the less-invasive procedure, the important quadriceps muscle and tendon are not disrupted as in traditional knee replacement. LifeART image ©2004 Lippincott Williams & Wilkins. All rights reserved.

Figure 2 - The skin incision for minimally-invasive quadriceps-sparing total knee replacement is typically about 4" in length, compared to about 8" or more for traditional total knee replacements.

Figure 3 - X-ray of a traditional total knee replacement. This operation is done for patients who have arthritis throughout the knee. Excellent long-term results are obtained in most patients.

Figure 4 - Model of a traditional total knee replacement. The patella (knee cap) is not shown in this model.

Figure 5 - X-ray of a partial, or unicompartmental, knee replacement. This operation is done for patients whose arthritis is limited to one side of the knee. It may be done through a very small incision, and recovery from this procedure is usually much quicker than that seen with traditional total knee replacement.

Figure 6 - Model of a partial knee replacement. This smaller implant leaves undamaged cartilage in other parts of the knee intact.

Figure 7 - Knee arthritis can affect any of the three compartments of the knee. Medial-sided knee pain, located on the part of the knee that faces the opposite knee, is the most common location for arthritic pain.

Figure 8 - Lateral knee pain, affecting the "outside" of the knee, is sometimes the result of arthritis of the knee.

Figure 9 - Pain behind the kneecap from arthritis may occur along with arthritis elsewhere in the knee, or in isolation. Isolated patellofemoral arthritis is the least common pattern of knee arthritis.

Figure 10 - This patient had rheumatoid arthritis and symptoms throughout her knee, resulting in the traditional total knee replacement pictured here.

Figure 11 - This patient's arthritis was confined to the medial ("inside") compartment of her knee on x-rays, and her pain was localized to that part of the knee as well. She was a good candidate for minimally-invasive partial knee replacement.

Figure 12 - Minimally-invasive partial knee replacement may be performed for either medial ("inside" of the knee) or lateral ("outside" of the knee) arthritis patterns, provided the symptoms are limited to that one part of the knee. X-rays of two knee replacements are shown here. On the left is a medial replacement, and on the right is a lateral replacement.

Figure 13 - Model of a total knee replacement. This implant may be inserted either using a traditional surgical approach, or through the minimally-invasive quadriceps-sparing technique, depending on factors unique to each patient.

Figure 14 - This patient had diffuse arthritis throughout his knee from an old fracture of the tibia (shinbone). It was treated with a traditional total knee replacement, rather than a minimally-invasive procedure, because of extensive scarring from prior

Figure 15 - This patient had rheumatoid arthritis and symptoms throughout her knee, resulting in the traditional total knee replacement pictured here.

Figure 16 - Model of a partial knee replacement. This smaller implant leaves undamaged cartilage in other parts of the knee intact.

Figure 17 - X-ray of a partial, or unicompartmental, knee replacement. This operation is done for patients whose arthritis is limited to one side of the knee. It may be done through a very small incision, and recovery from this procedure is usually much qu

Figure 18 - This clinical photograph shows a typical incision used to insert a minimally-invasive partial knee replacement. The average length of the incision used in this procedure is 3 inches. Smaller incisions help permit faster recovery, and lead to less post-operative pain, compared to traditional knee replacement surgery.

Figure 19 - The skin incision for minimally-invasive quadriceps-sparing total knee replacement is typically about 4? in length, compared to about 8? or more for traditional total knee replacements.

Figure 20 - In minimally-invasive quadriceps-sparing total knee replacement, the incision is much shorter, the kneecap is not everted, and the important quadriceps muscle and tendon are not divided. This may permit faster rehabilitation after knee replacem

Figure 21 - In traditional total knee replacement, the quadriceps tendon is divided along its length, and the kneecap is turned outward (everted, or ?dislocated?) in order to gain access to the knee joint. This photo shows a total knee replacement done thr

Summary

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, anti-inflammatory medications, or knee joint injections) 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 ways to insert a total knee replacement: the traditional approach, and the newer minimally-invasive (sometimes called quadriceps-sparing) approach.

Traditional total knee replacement involves a roughly 8” incision over the knee, a hospital stay of 3-5 days, and sometimes an additional stay in an inpatient rehabilitation setting before going home. The 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.

Minimally-invasive quadriceps-sparing total knee replacement is a new surgical technique that allows surgeons to insert the same time-tested, reliable knee replacement implants through a shorter incision using surgical approach that avoids trauma to the quadriceps muscle (see figure 1), which is the most important muscle group around the knee. This new technique, which is sometimes called quadriceps-sparing knee replacement uses an incision that is typically only 3-4” in length (see figure 2), and the recovery time is much quicker – often permitting patients to walk with a cane within a couple of weeks of surgery or even earlier. The less-traumatic nature of the surgical approach also may decrease post-operative pain and diminish the need for rehab and therapy compared to more traditional approaches.

The main potential benefits of this new technique include:

1. More rapid return of knee function. Patients who undergo this procedure seem to get muscle strength and control back more quickly than patients who have had traditional total knee replacement. (See Video) This is because the quadriceps muscle and tendon are not divided in the course of the surgical exposure like in traditional knee replacement, and the kneecap is not everted (flipped out of the way) as it is in traditional total knee replacement.
2. Smaller incision. While this procedure would not be worth performing for cosmetic benefits, many patients do prefer the shorter incision. Traditional knee replacement incisions often measure 8” or longer; minimally-invasive quadriceps-sparing knee replacement incisions are about 4” in length for most patients.
3. Decreased post-operative pain. (See Video)This may be a function of the smaller incision and the fact that the incision stays out of the important quadriceps muscle/tendon group.
4. Same reliable surgical implants as Traditional Knee Replacement. Much has been learned about implant design in the nearly 40-year history of contemporary knee replacement. Minimally-invasive quadriceps-sparing total knee replacement is an evolution of surgical technique, which permits the use of time-tested implant designs (see figures 3 and 4). This gives some reassurance that while the surgical approach is new, the implants themselves have a good proven track record.

The major apparent risks of the procedure compared to traditional total knee replacement:

1. The procedure is new. Though surgeons have studied the approach, the studies are recent and have replicated (repeated and verified) by only a few groups of surgeon-scientists. These studies give some insight into which patients and patterns of arthritis are most suitable for this procedure, the relative novelty of the approach it is likely that as time passes we will discover more about the risks and shortcomings of this technique. Also, even an experienced knee replacement surgeon will have performed many more surgeries through the traditional approach than through the less-invasive method; we know that the more procedures one does, the more reliable the results are.
2. The procedure is more challenging. Operating through a smaller surgical window takes some getting used to, and this can increase operative time compared to procedures performed using the traditional technique. This may increase the likelihood that an intra-operative injury to tendon or ligament might occur, which could compromise the result. This may also increase the likelihood of component malalignments, which could affect function and durability. However, two preliminary studies on this technique in fact found that these adverse outcomes did not take place.

For some patients, an implant other than a total knee replacement may be a reasonable choice. Partial knee replacements, sometimes called unicompartmental (partial) knee replacements (see figures 5 and 6), also have a long track record in this country and in Europe. Partial knee replacements have been around for decades and offer excellent clinical results, just like total knee replacements. Less invasive techniques are available to insert these smaller implants as well, but only a minority of knee replacement patients (about 10%) are good candidates for this procedure. Minimally-invasive partial knee replacement (mini knee) is the topic of another article on this website.

By contrast, the minimally-invasive quadriceps-sparing total knee replacement is appropriate for most patterns of knee arthritis.

Downloads

• Video: In recovery 30 minutes after MIS total knee replacement. (3.76 MB)
• Video: Ten days after quad sparing total knee replacement, walking without a cane. (1.50 MB)

View a patient skiing deep powder at Bridger Bowl, Montana, about 8 months after a minimally-invasive total knee replacement; note that not all patients are able to ski, and we do not recommend this activity to patients with knee replacements.

Characteristics of knee arthritis

There are over 100 types of arthritis, and all of them can affect the knee, and the knee is the most-commonly affected joint. Most patients who have arthritis are over age 50, but certain types and patterns of arthritis can affect younger patients. Arthritis of the knee causes pain, stiffness, and sometimes swelling. Patients with more advanced arthritis find that even simple daily activities like walking, arising from a chair, and performing self-care can be affected. Most patients with arthritis can achieve some measure of relief from activity modifications, pills, or joint injections; however, for some patients these remedies are insufficient to provide a satisfactory quality of life. These patients sometimes consider knee replacement surgery. More details about the common characteristics of knee arthritis follow below:

Pain
Pain is the most noticeable symptom of knee arthritis. In most patients, the pain gradually gets worse over time, but sometimes has more sudden “flares” where the symptoms get acutely severe. The pain is almost always worsened by weight-bearing and activity. In some patients, the pain becomes severe enough to limit even routine daily activities.

Stiffness
Morning stiffness is present in certain types of arthritis; patients with this symptom may notice some improvement in knee flexibility over the course of the day. Rheumatoid arthritis patients may experience more frequent morning stiffness than patients with osteoarthritis.

Swelling and warmth
Patients with arthritis sometimes will notice these symptoms. If the swelling and warmth are excessive, and are associated with severe pain, inability to bend the knee, and difficulty with weight-bearing, those signs might represent an infection. Such severe symptoms require immediate medical attention. Joint infection of the knee is discussed below.

Location
The knee joint has three “compartments” that can be involved with arthritis (see figure 7). Most patients have both symptoms and findings on X-rays that suggest involvement of two or more of these compartments--for example, pain on the lateral side (see figure 8) and beneath the kneecap (see figure 9). Patients who have arthritis in two or all three compartments, and who decide to get surgery, most often will undergo total knee replacement (see figure 10).

However, some patients have arthritis limited to one compartment of the knee--most commonly the medial side (see figure 11). When patients with one-compartment arthritis (also called “unicompartmental” arthritis) decide to get surgery, they may be candidates for minimally-invasive partial knee replacement (mini knee) (see figure 12).

Types

Inflammatory arthritis

This broad category includes a wide variety of diagnoses, including Rheumatoid arthritis, lupus, gout, and many others. It is important that patients with these conditions be followed by a qualified rheumatologist, as there are a number of exciting new treatments that may decrease the symptoms and perhaps even slow the progression of the joint damage.

Patients with inflammatory arthritis of the knee usually have joint damage in all three compartments, and therefore are not good candidates for partial knee replacement. However, inflammatory arthritis patients who decide to have total knee replacement have an extremely high likelihood of success; these patients often experience total or near-total pain relief following a well-performed joint replacement.

Osteoarthritis

Osteoarthritis is also called OA or “degenerative joint disease.” OA patients represent the large majority of arthritis sufferers. OA may affect multiple joints, or it may be localized to the involved knee. Activity limitations due to pain are the hallmarks of this disease.

OA patients who have symptoms limited to one compartment of the knee sometimes are good candidates for minimally-invasive partial knee replacement (mini knee).

Similar conditions

Meniscus tear

Sometimes patients with knee pain don't have arthritis at all. Each knee has two rings of cartilage called "menisci" (this is the plural form of "meniscus"). The menisci work similarly to shock absorbers in a car.

Menisci may be torn acutely, in a fall or as the result of other trauma, or they may develop degenerative tears from wear-and-tear over many years. Patients with meniscus tears experience pain along the inside or outside of the knee; sometimes the pain is worse with deep squatting or twisting. Popping and locking of the knee are also occasional symptoms of meniscus tears.

Since some of these symptoms may be present with arthritis, and the treatment of arthritis is different from that of meniscus tears, it is important to make the correct diagnosis. A good orthopaedic surgeon can distinguish the two conditions by taking a thorough history, performing a careful physical examination, and by obtaining imaging tests. X-rays and Magnetic Resonance Imaging (MRI) scans may be helpful in distinguishing these two conditions.

Joint infections

Also called infectious arthritis or septic arthritis, a joint infection is a severe problem that requires emergent medical (and often surgical) attention. If not treated promptly, knee infections can cause rapid destruction of the joint; in the worst cases, they can become life-threatening.

Symptoms of a knee joint infection include:

• severe pain,
• joint swelling and warmth,
• fevers, and
• marked inability to walk, bend the knee, or bear weight.

Patients who suffer from arthritis are not more likely to develop such infections. They may occur in anyone. Arthritis patients who develop such infections would notice a significant worsening in their pain, as well as some of the other symptoms listed above.

A physician will make the diagnosis of a joint infection based on history and physical examination, blood tests, and by sampling joint fluid from the knee.

Again, a joint infection is a serious condition that requires immediate medical attention.

Incidence and risk factors

Diagnosis

History and physical examination

An orthopaedic surgeon will begin the evaluation with a thorough history and physical exam. Based on the results of these steps, (s)he may order plain X-rays.

X-rays

If a patient has arthritis of the knee, it will be evident on routine X-rays of the joint. X-rays taken with the patient standing up are more helpful than those taken lying down, as the way the knee joint functions under load (i.e. standing) provides important treatment clues to the physician.

Also, plain X-rays will allow an orthopaedic surgeon to determine whether the arthritis pattern would be suitable for total knee replacement or for a different operation, such as minimally-invasive partial knee replacement (mini knee).

Medications

It is important to distinguish broadly between two types of arthritis: inflammatory arthritis (including Rheumatoid arthritis, lupus, and others) and non-inflammatory arthritis (such as osteoarthritis).

Although there is some level of inflammation present in all types of arthritis, conditions that fall into the category of true inflammatory arthritis are often very well managed with a variety of medications, and more treatments are coming out all the time. Individuals with rheumatoid arthritis and related conditions need to be evaluated and followed by a physician who specializes in those kinds of treatments, called a rheumatologist. Excellent non-surgical treatments (including many new and effective drugs) are available for these patients; those treatments can delay (or avoid) the need for surgery, and also help prevent the disease from affecting other joints.

So-called non-inflammatory conditions, including osteoarthritis (sometimes called degenerative joint disease), also sometimes respond to oral medications (either painkillers like Tylenol, or non-steroidal anti-inflammatory drugs like aspirin, ibuprofen, celebrex, or vioxx) but in many cases, symptoms persist despite that type of treatment.

It is important to avoid using narcotics (such as Tylenol #3, vicoden, percocet, or oxycodone) since they are have many side effects, are habit-forming, and make it harder to achieve pain-control safely and effectively after surgery, should that become necessary. Narcotics are designed for people with short-term pain (like after a car accident or surgery), or for people with chronic pain who are not surgical candidates. People who feel they need narcotics to achieve pain control should consider seeing a joint replacement surgeon (an orthopaedic surgeon with experience in knee replacements) to see whether surgery is a better option.

Nutritional supplements, like glucosamine and chondroitin, have been shown to decrease pain in many patients who use them. These products typically take 6-8 weeks to achieve their maximum effect. However, they do not work for all patients who try them, and despite what some advertisements suggest, they do not appear to regrow cartilage or reverse the arthritic process.

Joint injections, either with corticosteroids (“cortisone shots”) or with viscosupplements like Synvisc or Hyalgan, may also provide temporary relief. These products do not work in all people who try them, and there is some risk of infection associated with injecting the knee joint, though this is not very likely.

Exercises

There is little evidence to suggest that knee arthritis can be prevented or caused by exercises or activities, unless the knee was injured (or was otherwise abnormal) before the exercise program began. There is no evidence that, once arthritis is present in a knee joint, any exercises will alter its course.

However, exercise and general physical fitness have numerous other health benefits. Regular range of motion exercises and weight bearing activity are important in maintaining muscle strength and overall aerobic (heart and lung) capacity, and help prevent the development of osteoporosis, which can complicate later treatment. Certainly, people who are physically fit are more resilient and, in general, are more able to overcome the problems associated with arthritis. Physically fit people also tend to recover more quickly from surgery, should that eventually be necessary to treat the knee arthritis.

Possible benefits of minimally-invasive (quadriceps-sparing) total knee replacement

Regardless of whether a traditional total knee replacement or a minimally-invasive (quadriceps-sparing) total knee replacement is performed, the goals and possible benefits are the same: relief of pain, and restoration of function.

The large majority (more than 90 percent) of total knee replacement patients experience substantial or complete relief of pain once they have recovered from the procedure. The large majority walk without a limp, and most don’t require a cane, even if they used one before the surgery. It is quite likely that you know someone with a knee replacement who walks so well that you don’t know (s)he even had surgery! Frequently, the stiffness from arthritis also is relieved by the surgery. Very often, the distance one can walk will improve as well, because of diminished pain and stiffness. The enjoyment of reasonable recreational activities, such as golf, dancing, traveling, and swimming almost always improves following total knee replacement.

However, there are some potential benefits of the newer, less-invasive total knee technique over the traditional technique of total knee replacement.

The main potential benefits of this new technique include:

1. More rapid return of knee function. Patients who undergo this procedure seem to get muscle strength and control back more quickly than patients who have had traditional total knee replacement. This is because the quadriceps muscle and tendon are not divided in the course of the surgical exposure like in traditional knee replacement, and the kneecap is not everted (flipped out of the way) as it is in traditional total knee replacement.
2. Smaller incision. While this procedure would not be worth performing for cosmetic benefits, many patients do prefer the shorter incision. Traditional knee replacement incisions often measure 8” or longer; minimally-invasive quadriceps-sparing knee replacement incisions are about 4” in length for most patients.
3. Decreased post-operative pain. This may be a function of the smaller incision and the fact that the incision stays out of the important quadriceps muscle/tendon group.
4. Same reliable surgical implants as Traditional Knee Replacement. Much has been learned about implant design in the nearly 40-year history of contemporary knee replacement. Minimally-invasive quadriceps-sparing total knee replacement is an evolution of surgical technique, which permits the use of time-tested implant designs. This gives some reassurance that while the surgical approach is new, the implants themselves have a good proven track record.

Types of surgery recommended

Joint replacement surgery is the most effective method for restoring comfort and function to knees damaged by severe arthritis. When the normally smooth surfaces of the knee joint are severely damaged by arthritis, injury or surgery, total knee replacement may be the most effective method for restoring comfort and function to the joint. For a minority of patients with arthritis, a minimally-invasive partial knee replacement is an option instead of total knee replacement, but most patients with knee arthritis who undergo surgery are better served with total knee replacement.

Other surgical options, such as arthroscopy or “clean up” operations have not been shown to give lasting benefit.

Knee fusion can stabilize the joint and decrease pain, but does not allow motion at the knee joint.

For selected younger and more active patients, realigning the joint using a procedure called osteotomy may be appropriate; however, the durability and pain relief of this procedure does not seem to measure up to joint replacement, particularly in older patients.

Who should consider minimally-invasive (quadriceps-sparing) total knee replacement?

Joint replacement surgery is considered when:

• the arthritis is a major problem for the patient,
• the patient is sufficiently healthy to undergo the procedure,
• the patient understands and accepts the risks and alternatives,
• there is sufficient bone and tendon to permit the surgery, and
• the surgeon is experienced in knee replacement surgery.

What happens without surgery?

Surgical options

If a knee surgeon and a patient decide that non-operative treatments have failed to provide significant or lasting relief, there are sometimes different operations to choose from.

Total knee replacement

Long considered the “gold standard” operation for knee arthritis, total knee replacement is still by far the most commonly-performed joint replacement procedure (see figure 13). It is most suitable for middle-aged and older people who have arthritis in more than one compartment of the knee (see figures 14 and 15), and who do not intend to return to high-impact athletics or heavy labor. Results of this procedure generally are excellent, with 90-95% of total knee replacements continuing to function well more than 10 years after surgery.

There are now several ways to perform total knee arthroplasty:

Minimally-Invasive Quadriceps-Sparing Total Knee Replacement

This is a new technique that permits insertion of the joint replacement implants through a short incision – typically about 4” in length – and allows the surgeon to do so without disturbing the quadriceps muscle or tendon. The shorter incision, but more importantly the avoidance of the quadriceps muscle and tendon, may result in less pain, a quicker rehabilitation, and earlier restoration of function. However, this procedure may not be appropriate for all patients with knee arthritis who undergo knee replacement; patients who are heavier, have osteoporosis in addition to arthritis, and who have significant joint deformity or stiffness may be better served with traditional approaches to total knee replacement.

Traditional Total Knee Replacement 

The joint replacement in inserted using an incision that typically measures 8”-10” in length over the front of the knee. The quadriceps tendon and/or muscle is entered and the kneecap is moved out of the way to permit the surgeon to see the inside of the knee fully and clearly. Restoring range of motion and quadriceps strength is the biggest part of the patient’s rehabilitation after the surgery. This approach has been used for over three decades, with excellent results. It is adaptable, and permits surgeons to perform the procedure in patients who are heavy, who have joint deformity, or who have severe stiffness.

But not every patient with knee arthritis needs (or should have) total knee replacement. There are many other surgical options available for patients with certain patterns of knee arthritis. These include:

Minimally-invasive partial knee replacement (unicompartmental knee)

Patients who are of appropriate age--certainly older than age 40, and older is better--and who have osteoarthritis limited to one compartment of the knee may be candidates for an exciting new surgical technique, minimally-invasive partial knee replacement (mini knee) (see figures 16, 17, and 18). Partial knee replacements have been done for over 20 years, and the “track record” on the devices used for this operation is excellent. The new surgical approach, which uses a much smaller incision than traditional total knee replacement, significantly decreases the amount of post-operative pain, and shortens the rehabilitation period. The decision of whether this procedure is appropriate for a specific patient can only be made in consultation with a skillful orthopaedic surgeon who is experienced in all techniques of knee replacement.

Minimally-invasive partial knee replacement (mini knee) is not for everyone. Only certain patterns of knee arthritis are appropriately treated with this device through the smaller approach.

Generally speaking, patients with inflammatory arthritis (like Rheumatoid arthritis or lupus), and patients with diffuse arthritis all throughout the knee should not receive partial knee replacements.

Patients who are considering knee replacements should ask their surgeon whether minimally-invasive partial knee replacement (mini knee) is right for them.

Knee arthroscopy

If X-rays don’t show very much arthritis, and the surgeon suspects (or has identified by MRI) a torn meniscus, knee arthroscopy may be a good choice. This is a relatively minor procedure that is usually done as an outpatient, and the recovery is fairly quick in most patients.

However, if X-rays demonstrate a significant amount of arthritis, this may not be a good choice. Knee arthroscopy for arthritis fails to relieve pain in about half of the patients who try it.

Osteotomy

For younger patients (typically under age 40, but this age cutoff is flexible) who desire to return to a high level of athletic activity or physical work, a procedure called osteotomy (which means “cutting the bone”) might be worth considering. This option is suitable only if the arthritis is limited to one compartment of the knee (for more information about arthritis in one compartment of the knee, see the "Location" section on page 2 of this article).

Osteotomy involves cutting and repositioning one of the bones around the knee joint. This is done to re-orient the loads that occur with normal walking and running so that these loads pass through a non-arthritic portion of the knee. That’s why it doesn’t work well if more than one compartment of the knee is involved--in those patients, there is no “good” place through which the load can be redistributed.

Knee fusion

Knee fusion, also called “arthrodesis,” permanently links the femur (thigh bone) with the tibia (shin bone), creating one long bone from the hip to the ankle. It removes all motion from the knee, resulting in a stiff-legged gait.

Because there are so many operations that preserve motion, this older procedure is seldom performed as a first-line option for patients with knee arthritis. It is sometimes used for severe infections of the knee, certain tumors, and patients who are too young for joint replacement but are otherwise poor candidates for osteotomy.

Video: Minimally-Invasive Joint Replacement Video

Effectiveness

Current evidence suggests that when total knee replacements are done well, in properly selected patients, success is achieved in the large majority of patients, and the implant serves the patient well for many years.

Many studies show that 90-95 percent of total knee replacements are still functioning well 10 years after the surgery. Most patients walk without a cane, most can do stairs and arise from chairs normally, and most resume their desired level of recreational activity.

The goal of minimally-invasive quadriceps-sparing total knee replacement is to capitalize on the decades of experience surgeons have gained in total knee implant design and intra-operative ligament balancing, but provide patients with a faster recovery and less post-operative pain. The same knee replacement implants and materials are used, the point of attachment to the bones is the same (bone cement), and the same attention to surgical detail, limb alignment, and ligament balancing are given during the newer, less-invasive procedure as during the traditional approach. It is important to remember that this is a new procedure compared to traditional total knee replacement, and as a result, we do not have long-term follow-up on outcomes. However, short term studies on knee component and limb alignment and peri-operative complications have found results with those endpoints that are comparable to traditional approaches while providing patients with faster rehabilitation.

Regardless of the technique used to insert the knee replacement (traditional or minimally-invasive), in the event that a total knee replacement requires re-operation sometime in the future, it almost always can be revised (re-done) successfully. However, results of revision knee replacement are typically not as good as first-time knee replacements.

There is good evidence that the experience of the surgeon correlates with outcome in total knee replacement surgery; for this reason, it is best to have the initial surgery done by an individual who is experienced (fellowship-trained, and with a practice that focuses on knee replacement) in this kind of work.

Likewise, the new technique of minimally-invasive quadriceps sparing knee replacement should only be performed by surgeons who have taken special training on the instruments and surgical approaches, and who have experience using less-invasive surgical techniques around the knee.

Surgeons with this level of experience have been shown to have fewer complications and better results than surgeons who haven’t done as many knee replacements. It is therefore important that the surgeon performing the technique be not just a good orthopaedic surgeon, but a specialist in knee replacement surgery and in less-invasive joint replacement.

Urgency

Risks

Like any major surgical procedure, total knee replacement is associated with certain medical and surgical risks. Although major complications are uncommon, they may occur; the possibilities include blood clots, bleeding, and anesthesia-related or medical risks such as cardiac risks, stroke, and in rare instances (large studies have calculated the risk to be less than 1 in 400), death.

Risks specific to knee replacement include infection (which may result in the need for more surgery), nerve injury, the possibility that the knee may become either too stiff or too unstable to enjoy it, a chance that pain might persist (or new pains might arise), and the chance that the joint replacement might not last the patient's lifetime or might require further surgery.

Minimally-invasive quadriceps-sparing total knee replacement is a new procedure. For this reason, it is fair to say that the specialty will need to pay close attention to results to make sure they are as good or better than the traditional techniques that have been in common use for quite some time now. However, preliminary studies on the technique have shown no increases in surgical or medical risk with this approach compared to traditional total knee arthroplasty, and these same studies have shown benefits in terms of post-operative pain and early recuperation and rehabilitation after surgery.

While the overall list of complications may seem long and intimidating, the overall frequency of major complications following total knee replacement is low, usually less than 5 percent (one in 20). Obviously, the overall risk of surgery is dependent both on the complexity of the knee problem but also on the patient's overall medical health.

The major apparent risks of the minimally-invasive quadriceps-sparing procedure compared to traditional total knee replacement include the following:

1. The procedure is new. Though surgeons have studied the approach, the studies are recent and have replicated (repeated and verified) by only a few groups of surgeon-scientists. These studies give some insight into which patients and patterns of arthritis are most suitable for this procedure, the relative novelty of the approach it is likely that as time passes we will discover more about the risks and shortcomings of this technique. Also, even an experienced knee replacement surgeon will have performed many more surgeries through the traditional approach than through the less-invasive method; we know that the more procedures one does, the more reliable the results are.
2. The procedure is more challenging. Operating through a smaller surgical window takes some getting used to, and this can increase operative time compared to procedures performed using the traditional technique. This may increase the likelihood that an intra-operative injury to tendon or ligament might occur, which could compromise the result. This may also increase the likelihood of component malalignments, which could affect function and durability. However, two preliminary studies on this technique in fact found that these adverse outcomes did not take place.

Managing risk

Many of the major problems that can occur following traditional or minimally-invasive total knee replacement can be treated. The best treatment, though, is prevention. An orthopaedic surgeon will use antibiotics before, during and after surgery to minimize the likelihood of infection. (S)he will take steps to decrease the likelihood of blood clots, such as early patient mobilization and use of blood-thinning medications in some patients. Patients are evaluated by a good internist and/or anesthesia provider in advance of the surgery, in order to decrease the likelihood of a medical or anesthesia-related complication. Good surgical technique can help minimize the knee-specific risks--so choosing a fellowship-trained and experienced knee replacement surgeon is important.

Again, the overall likelihood of a severe complication is typically less than 5 percent when such steps are taken.

Preparation

Patients undergoing total knee replacement surgery usually will undergo a pre-operative surgical risk assessment. When necessary, further evaluation will be performed by an internal medicine physician who specializes in pre-operative evaluation and risk-factor modification. Some patients will also be evaluated by an anesthesiologist in advance of the surgery.

Routine blood tests are performed on all pre-operative patients; chest X-rays and electrocardiograms are obtained in patients who meet certain age and health criteria, as well.

Some patients opt to predonate their own blood in advance of surgery to try to minimize the likelihood that transfusions from the blood bank will be needed. Each patient’s individual circumstances need to be considered when deciding whether this is worthwhile.

Surgeons will often spend time with the patient in advance of the surgery, making certain that all the patient's questions and concerns, as well as those of the family, are answered.

Timing

Costs

The surgeon's office should provide a reasonable estimate of:

• the surgeon's fee,
• the hospital fee, and
• the degree to which these should be covered by the patient's insurance.

Surgical team

Minimally-invasive quadriceps-sparing total knee replacement requires an experienced orthopaedic surgeon and the resources of a large medical center. Patients should inquire as to the number of knee arthroplasty procedures that the surgeon performs each year overall, and how many minimally-invasive knee replacements the surgeon has performed.

Some patients have complex medical needs and around surgery often require immediate access to multiple medical and surgical specialties and in-house medical, physical therapy, and social support services.

Finding an experienced surgeon

There is good evidence that the experience of the surgeon performing partial knee replacement affects the outcome. It is important that the surgeon be experienced--and preferably fellowship-trained--knee replacement surgeon.

Some questions to consider asking your knee surgeon:

• Are you board certified in orthopaedic surgery?
• Have you done a fellowship (a year of additional training, beyond the five years required to become an orthopaedic surgeon) in joint replacement surgery?
• How many knee replacements do you do each year?
• How many minimally-invasive knee replacements have you performed?

Facilities

Technical details

Minimally-invasive quadriceps-sparing total knee replacement surgery begins by performing a sterile preparation of the skin over the knee to prevent infection, followed by inflation of a tourniquet to prevent blood loss during the operation.

Next, a well-positioned skin incision – typically about 4” in length (see figure 19), though this varies with the patient’s size – is made down the front of the knee just adjacent to the kneecap, and the knee joint is inspected and preliminary ligament balancing is performed.

Next, specially-designed alignment rods and cutting jigs – which are smaller and easier to pass through the smaller incision than those used for traditional total knee replacement – are used to remove enough bone from the end of the femur (thigh bone), the top of the tibia (shin bone), and the underside of the patella (kneecap) to allow placement of the joint replacement implants. Proper sizing and alignment of the implants, as well as final balancing of the knee ligaments, all are critical for normal post-operative function and good pain relief. Again, these steps are complex, and considerable experience in minimally-invasive knee replacement is required in order to make sure they are done reliably, case after case. Provisional (trial) implant components are placed, without bone cement, to make sure they fit well against the bones and are well aligned; at this time, good function--including full flexion (bend), extension (straightening), and ligament balance--is verified.

Finally, the bone is cleaned using saline solution and the joint replacement components are cemented into place using polymethylmethacrylate bone cement (see figure 20). The surgical incision is closed using stitches and staples.

Anesthetic

Length of minimally-invasive (quadriceps-sparing) total knee replacement

Pain and pain management

Whenever possible, we use a spinal anesthetic, with a long-acting morphine product to provide pain relief for up to 24 hours after surgery. Beyond that, pain medications by vein or in pill form are used to permit early, rapid rehabilitation.

Alternatively, an epidural catheter (a very thin, flexible tube placed into the lower back at the time of surgery) to manage post-operative discomfort. This device is similar to the one that is used to help women deliver babies more comfortably. As long as the epidural is providing good pain control, we leave it in place for two days after surgery. After the epidural is removed, pain pills usually provide satisfactory pain control. Patients who have epidural or spinal anesthesia can expect to walk with crutches or a walker, and to take the knee through a near-full range of motion starting on the day after surgery. In the days that follow, the patient is transitioned on to pain pills to allow rehabilitation and rapid recovery following minimally-invasive quadriceps-sparing total knee replacement.

Some patients are not candidates for spinal or epidural anesthetics, or choose not to have them. These patients receive pain medications by vein for the first day or two, and then can go home on pain pills following minimally-invasive quadriceps-sparing total knee replacement.

Use of medications

Following discharge from the hospital, most patients will take oral pain medications--usually Percocet, Vicoden, or Tylenol #3--for one to three weeks after the procedure, mainly to help with physical therapy and home exercises for the knee.

Aggressive rehabilitation is desirable following this procedure, and a high level of patient motivation is important in order to get the best possible result. “Minimally-invasive” does not mean “non-invasive” or “minor”; it is important to realize that even with the newer technique, the biggest key to recovery is a motivated patient who is diligent about his/her rehabilitation and home exercises. Pushing through a certain amount of discomfort or pain is part of recovery from any knee replacement.

Oral pain medications help this process in the weeks following the surgery.

Most patients take some narcotic pain medication for between 2 and 6 weeks after surgery. Patients should not drive while taking these kinds of medications.

Effectiveness of medications

While any surgical procedure is associated with post-operative discomfort, most patients who have had the total knee replacements say that the pain is very manageable with the pain medications, and the large majority look back on the experience and find that the pain relief given by knee replacement is well worth the discomfort that follows this kind of surgery.

Minimally-invasive quadriceps-sparing total knee replacement seems to be associated with less pain than traditional total knee replacement. However, it is important to realize that it is a real surgical procedure, and a good outcome depends on a motivated patients who is willing to push through a certain amount of discomfort to get the best possible knee motion and outcome after surgery.

Important side effects

Hospital stay

The average hospital stay after traditional total knee replacement is three days, and most patients spend several more days in an inpatient rehabilitation facility. Patients who prefer not to have inpatient rehabilitation may spend an extra day or two in the hospital before discharge to home.

The overall duration of hospitalization after minimally-invasive quadriceps-sparing total knee replacement typically is 48 hours; some patients need to stay for a third day, but many do not. Patients generally are discharged directly home from the hospital after minimally-invasive quadriceps-sparing total knee replacement, and don't require any inpatient rehabilitation. Ultimately, the length of hospital stay is individualized to meet each patient’s needs, and discharge occurs when the patient can perform the necessary range of motion exercises, and when home support systems for the patient are in place.

Recovery and rehabilitation in the hospital

Patients begin range-of-motion exercises on the day following surgery. Patients are encouraged to sit, stand, and walk as much as possible in the days following the procedure. Patients who regain good range-of-motion early (defined as near-full extension and bend beyond 90 degrees in the first day or two after surgery) typically do very well, so this is emphasized in physical therapy sessions that take place twice daily after surgery. Most patients begin with a walker or crutches, and transition to a cane is encouraged, and permitted as soon as patients tolerate it, provided their balance is good. Therapists instruct all patients in how to perform a home exercise program to allow recovery to continue after discharge.

Downloads

• Video: Ten days after quad sparing total knee replacement, walking without a cane. (1.50 MB)
• Video: In recovery 30 minutes after MIS total knee replacement. (3.76 MB)

Hospital discharge

The average hospital stay after minimally-invasive total knee replacement is two days, with some patients staying three. Patients generally are discharged to their homes directly from the hospital (again, usually after a 48-hour stay), and generally do not require inpatient rehabilitation. Sometimes the stay is even shorter.

At the time of discharge, the patient should be relatively comfortable on oral medications, should have a dry incision, should understand their exercises and should feel comfortable with the plans for managing the knee. Management of these limitations requires advance planning to accomplish the activities of daily living during the period of recovery.

Convalescent assistance

Most patients will go home following their hospital stay. Home physical therapy, typically 3 times per week, is initiated as soon as possible following hospital discharge.

Patients are encouraged to walk as normally as possible immediately following minimally-invasive quadriceps-sparing total knee replacements. Most people use crutches or a walker for a week, and then a cane for another week or so beyond that. Most people are walking nicely by about two weeks after surgery (see video, above).

Patients are allowed to shower as soon as the surgical incision has been dry for a day or so.

Patients should not resume driving until they feel their reflexes are completely normal, and until they feel they can manipulate the control pedals of the vehicle without guarding from knee discomfort. Certainly, patients should not drive while taking narcotic-based pain medications. On average, patients are able to drive between three and six weeks after the surgery.

Physical therapy

Can rehabilitation be done at home?

All patients are given a set of home exercises to do between supervised physical therapy sessions, and the home exercises make up an important part of the recovery process. However, supervised therapy--which is best done in an outpatient physical therapy studio--is extremely helpful, and those patients who are able to attend outpatient therapy are encouraged to do so.

For patients who are unable to attend outpatient physical therapy, home physical therapy is arranged.

Usual response

No two patients are alike, and recovery varies somewhat based on the complexity of the knee reconstruction, and the patient’s health, fitness, and level of motivation.

Most people walk using crutches or a walker for 2 weeks, then use a cane for about 2 more weeks.

Most patients obtain and keep at least 90 degrees of motion (bending the knee to a right angle) by a day or two after surgery, and most patients ultimately get more than 110 degrees of knee motion.

Most patients can return to sedentary (desk) jobs by about 4 weeks; return to more physical types of employment must be addressed on a case-by-case basis.

Most patients are back to full activities--without the pain they had before surgery--by about two months after the operation.

Risks

Duration of rehabilitation

Returning to ordinary daily activities

Most patients are walking unassisted following this procedure by about a two weeks after surgery (see video).

Most patients can return to desk work, at least for part days, by about a three weeks after surgery.

Downloads

• Video: Ten days after quad sparing total knee replacement, walking without a cane. (1.50 MB)

Long-term patient limitations

The goal of total knee replacement is to return patients to a high level of function without knee pain. The large majority of patients are able to achieve this goal. However, since the joint replacement components have no capacity to heal damage from injury sustained after surgery, we offer some common-sense guidelines for athletic, leisure, and workplace activities:

Recommended:

• Swimming
• Water aerobics
• Cross-country skiing or Nordic Track
• Cycling or stationary bike
• Golf
• Dancing
• Sedentary occupations (desk work)

Permitted when the patient finds them comfortable:

• Hiking
• Gentle doubles tennis
• Gentle downhill skiing
• Light labor (jobs that involve driving, walking or standing but not heavy lifting)

Not recommended:

• Jogging or running
• Impact exercises
• Sports that require twisting/pivoting (aggressive tennis, basketball, racquetball)
• Contact sports
• Heavy labor

Since the joint replacement includes a bearing surface, which potentially can wear, walking or running for fitness are not recommended. Some patients feel well enough to do this, and so need to exercise judgment in order to prolong the life-span of the implant materials. Swimming, water exercises, cycling and cross country skiing (and machines simulating it, like Nordic Track) can provide a high level of cardiovascular and muscular fitness without excessive wear on the prosthetic joint materials.

Costs

Summary of minimally-invasive (quadriceps-sparing) total knee replacement for knee arthritis

Total knee replacement is a reliable surgical technique in which the painful arthritic surfaces of the knee joint are replaced with well-engineered bearing surfaces. Pain is substantially improved and function regained in more than 90% of patients who have the operation.

Minimally-invasive quadriceps-sparing total knee replacement is a new technique for implanting well-tested total knee replacement components while minimizing post-operative pain and the time to full recovery. The length of the surgical incision, while not a goal of the procedure, is about half as long using the minimally-invasive approach compared to traditional total knee replacement approaches. One needs to remember that this is a new technique, and although preliminary studies are promising, it is likely we will continue to learn more about this procedure as time passes, and there may be risks to this approach that are not fully appreciated at this time.

Like any major procedure, there are risks to total knee surgery, and the decision to have a knee replacement must be considered a quality-of-life choice that individual patients make with a good understanding of what those risks are.

Knee replacement is a surgical technique that has many variables; like most areas of medicine, ongoing research will continue to help the technique evolve. It is important to learn as much as possible about the condition and the treatment options that are available before deciding whether--or how--to have a knee replacement done. While many of the changes now being explored in the field of total knee replacement may eventually be shown to be legitimate advances – perhaps including alternative bearing surfaces – it is important to compare them carefully to traditional total knee replacement performed using well established techniques, which we know are 90-95% likely to provide pain relief and good function for more than 10 years after the surgery.

Surgery for knee arthritis at the University of Washington