Knee Surgery

Diagnosing Knee Arthritis

Arthritis of the knee is a common underlying cause for knee replacement surgery. Here’s what you should know.

How is worn cartilage diagnosed?

Symptoms such as pain, swelling, stiffness, lack of movement, and grinding in the knee can suggest that knee cartilage is no longer smooth. X-rays are a common way of diagnosing diseased cartilage in the knee. The X-rays show the bones around the joint. The cartilage layer cannot be seen on X-rays, and shows up as a space between the femur and tibia bones.

In a healthy knee, this space is about a quarter of an inch thick. When joint space taken up by cartilage is destroyed by arthritis, X-rays will show joint-space narrowing. With significant cartilage loss, the bones may touch each other; doctors call this finding “bone-on-bone” on the X-rays.

Over time, cysts and bone spurs may form around the knee. Left untreated, the leg can get so deformed that it appears to be either bow-legged or knock-kneed.

Are there other ways to see the extent of damage to knee cartilage?

MRI scans are a special X-ray study that can diagnose diseased cartilage somewhat more accurately and at an earlier point than plain X-rays. Another method includes actually looking inside the knee during a procedure called “knee arthroscopy.” This involves the surgeon placing a small camera in the knee and inspecting the cartilage.

Before Knee Surgery

Health Considerations Before Knee Surgery

When you’re getting ready for a knee operation, here are some important things to know, especially since knee surgery has possible complications.

What do I need to do to prepare for knee surgery?

Reading the information on this site, communicating with your surgical team, and paying close attention to the checklists will best help you prepare for knee replacement surgery. The importance of preparation and information to successful surgery cannot be overemphasized.

What health conditions must be considered before undergoing surgery?

Some patients have unusual problems, such as HIV infection, hemophilia, cancer, bleeding disorders, liver or kidney transplants, enzyme disorders, and other conditions that require specialty consultations before surgery. If these considerations apply to you, your medical team will work with you to obtain the necessary testing and treatment prior to surgery.

What medical testing is needed prior to knee replacement surgery?

Pre-surgical checks are essential for your safety and it is unwise to short-circuit them; they are comparable to pre-flight checks that every responsible pilot makes before taking off. Out-of-town patients, or those traveling long distances, can have local doctors perform these checks. Usually, your medical team will work with your doctors to expedite this.

The typical pre-surgical checks are listed below; your doctor may include others.

Medical Check: Prior to your surgery, you should see an internal medicine specialist to identify and manage your health risks. Examples of increased risks are heart and lung disease, tooth and gum disease, infection, obesity, and diabetes. That is why patients should undergo testing and clearance by a medical doctor prior to knee replacement surgery.

Dental Check: A dental check-up is necessary to identify any hidden infection in your teeth or gums. Such infections must be treated before knee replacement to eliminate the risk that bacteria from decayed teeth enter the bloodstream and end up infecting the knee implants. If you are traveling from out of town, visit your dentist and forward the information to your surgeon.

Heart Check: If there is any reasonable suspicion of heart disease based on your history, it is best to find out ahead of time if your heart is healthy enough for knee replacement surgery. Heart disease is usually silent; patients do not have symptoms until the heart is stressed. If indicated, you will be asked to see a cardiologist before surgery for clearance.

What if I have bowel problems?

Pre-existing trouble with constipation usually leads to constipation and related problems after knee replacement. If you regularly take supplements to encourage bowel movements, let your doctor know so they can plan accordingly, since medicines used during and after surgery can result in serious constipation.

You will be given a stool softener before surgery to avoid problems with constipation later. Even so, you can probably expect disturbance of bowel patterns and at least some degree of constipation after knee replacement surgery.

How does diabetes affect my surgery?

Blood glucose levels over 200 will lead to poor wound healing and increased risk of infection. Therefore, it is critical that your diabetes is under control prior to surgery. A medical consultation and lab data before surgery will help your team to ensure your diabetes is controlled and your surgical risk is minimized.

Does osteoporosis affect the success of a total knee replacement?

No. If bone has severe osteoporosis, it may not be possible to use an un-cemented prosthesis. However, the cemented version of total knees can be implanted in nearly every type of bone, including bone that has osteoporosis, and the outcomes are very successful.

What about alcohol and drug use?

Regular alcohol consumption should be disclosed to your anesthesiologist and surgeon ahead of time. Alcohol withdrawal can happen to anyone, regardless of economic or social background. When it happens, it can be life threatening and can complicate your recovery from surgery. If your physicians know about alcohol consumption, they can take steps to avoid withdrawal. The same is true of recreational drugs. Be sure to talk about this with the anesthesia doctor.

What if I am a smoker?

Smoking increases the chance of lung complications during and after surgery, delays wound healing, increases the risk of complications after surgery, and increases the odds of residual knee pain even after successful knee replacement. Therefore, you should try to stop smoking, both for your general health, and to improve the odds of a successful result from knee replacement. Most hospitals are smoke-free, and you may not be able to smoke on the premises.

Does my body weight affect knee replacement?

Obesity will increase the risk of complications from surgery, such as blood clots and slower wound healing. Ideally, your weight should be within reasonable limits before knee replacement surgery. In some cases, for excessively heavy patients, knee replacement is not an option without drastic weight reduction, such as with gastric bypass surgery.

That said, many people are somewhat overweight and unable to lose weight while dealing with a painful arthritic knee. The knee components are designed to handle enormous loads, and are safe, even in very heavy people. There is no evidence to suggest that the components loosen up prematurely, or wear out prematurely in heavy people.

Exercise Before Surgery

What about dieting and exercising before surgery?

Maintain a nutritionally sound diet including a variety of foods in preparation for surgery. Crash dieting is not necessary; rather, regular exercise will help control weight and improve overall health.

Exercise before surgery, done within reason, and within the capability of the patient, will improve the recovery from knee surgery. Therefore, a reasonable exercise program to strengthen your thigh and calf muscles before knee replacement surgery is the best thing you can do to speed up your recovery.

How can exercise before the surgery help my recovery after?

Exercising and strengthening the thigh and leg muscles before the operation will result in faster recovery and return to function, with less suffering, struggle, depression, and mood swings. Consultation with a physical therapist before surgery can be very useful.

The reason exercise helps is that the knee, even if worn out, is a living joint. Living tissues respond positively to physiologic stress, and exercise is known to improve self-perception, esteem, and outlook.

Preparing for the Hospital

When do I first visit the hospital?

About a week or so before surgery, you will visit the pre-op department in the hospital. This visit is to read and sign consents for the surgery, for the anesthesia, and for blood products (if needed). You will have lab tests, possibly a chest X-ray, and an electrocardiogram. Please make a list of your medications and their dosages prior to this visit.

At this visit, you will be instructed on where to report on the morning of surgery. You will receive instructions on not eating or drinking after midnight the night before your surgery. This includes chewing gum and hard candy.

Keep in mind that surgery schedules change often; this is why the exact timing of the operation is not known until the day before. If you have a special preference, such as being the first in the day, or last, or in between, simply let the surgeon know and they will do their best to accommodate.

When will I be assigned a surgery time?

The hospital will contact you a day before the surgery to tell you what time to arrive at the hospital. Surgery schedules tend to change, which is why most hospitals will confirm the exact surgery time only a day or so before the operation. Please arrive early. The actual operation will usually be less than an hour in duration, but preparation takes much longer.

When do I see the anesthesiologist?

On the morning of your surgery, you will see an anesthesia doctor (anesthesiologist) who will have already reviewed your medical records. If your medical condition so requires, your surgeon will have consulted with the anesthesia doctor ahead of time. This doctor will inquire about your health and plan the anesthetic technique, including any regional nerve pain blocks. If you know of a particular anesthesiologist at the hospital whom you would prefer to provide this service, simply let someone on your medical team know ahead of time.

Should I donate my blood for surgery?

No. This is not necessary since not everyone needs a blood transfusion after knee replacement. If you have religious convictions against blood products, let your doctor know so they can arrange to recycle your own blood. Blood loss differs from patient to patient, and pre-existing conditions such as anemia and other diseases can affect the odds of needing blood after surgery.

As a general rule, major bone surgery is associated with blood loss, but it is impossible to say how much blood a particular patient will lose. If needed, blood transfusions today are very safe and effective.

Preparing for the Return Home

Do I need someone to stay with me after surgery?

If you live alone, an adult friend or relative should stay with you, in addition to the home health nurse visits during the week. For very elderly patients and patients with other health problems, a stay in a rehabilitation unit or a nursing facility may be necessary.

You might consider local home health agencies prior to coming to the hospital. If you have private insurance, you will need to make sure you choose a home health agency contracted with your insurance. The best time to do this is before you have surgery. Ask your doctor about these resources; they can arrange many of these things for you to ensure a smooth transition to your home.

How long do I need someone to stay with me after surgery?

You should plan on about two to four weeks, depending on your individual circumstances and available resources. During the first month, a home health nurse will visit you several times a week. Having someone with you can help with daily activities and chores, even though you will be able to walk and transfer yourself by the time you leave the hospital.

Where can I get a disabled parking sticker?

Your doctor should have forms that allow you to get a temporary disabled parking placard. A permanent disabled placard is not necessary after knee surgery, since the new knee is designed to increase your mobility. Some patients need a few weeks or months of parking in disabled zones, and others do not.

How do I prepare my home for after surgery?

Prior to surgery it is a good idea to take a close look at your home environment to determine if it is “user friendly” for someone on crutches or a walker. Modifications and equipment needs can be addressed ahead of time to ease your return home.

How do I prepare my home for after surgery?

Examine your home environment to see if it is user-friendly for crutches or a walker. Modifications and equipment needs often include the following:

Remove loose throw rugs, runners, area rugs in pathways. They can get tied up in the wheels of a walker, catch on a crutch tip or slide when stepped on.
Moving furniture to widen pathways and making sure doors open fully will make it easier for you to navigate with a walker or crutches. Bathroom doors are often too narrow to get through. Your physical therapist will instruct you in a safe technique to use.
A toilet riser, commode, grab bar on wall, or arm rests that easily attach to a toilet may be helpful as getting up and down may be difficult initially.
A step-in shower is the easiest to access. Many have seats built right in. If you have a bathtub only or tub/shower combination, a portable shower chair may be necessary for about a month. Having a grab bar is also recommended for optimum safety. Towel racks are not designed to hold the body’s weight and do not replace a grab bar.
Having at least one rail on stairways to provide support is recommended.
Night lights are recommended for all pathways used after dark.
A portable telephone comes in handy when you are alone at home.

Medication Use Before Surgery

Can my doctor fill narcotics medications until my surgery?

Before surgery, your physician can prescribe medications that are non-narcotic and non-addictive. These typically include anti-inflammatory medications and some light narcotic pain medications.

Any addictive drugs, such as narcotic pain-killers, should be obtained from your primary care doctor before surgery. Your primary care doctor and surgical team should be aware of all your medications, especially narcotic medicines.

When, and what medicines, should I stop?

In consultation with anesthesia and the pre-surgical medical consult, you will be advised personally which medications to stop in anticipation of surgery, and when to stop. The following are some general guidelines:

Ten days before surgery, stop taking blood thinning medications, such as clopidogrel bisulfate, ticlopidine, or aspirin, as well as vitamins, nutritional supplements, herbal supplements, fish oil, and anti-inflammatory medications, such as ibuprofen.
Five days before surgery, stop taking warfarin. This is a blood thinner that is usually prescribed for conditions such as blood clots, strokes, and irregular heart rhythm.
Other medications can be continued until the day of surgery. If you are taking steroids, chemotherapy, or medications for rheumatoid arthritis (such as methotrexate), you will be told when to stop those.
If a medication is not listed here, check with your internist or family doctor. You can also discuss these with your surgeon, the anesthesia staff, or the pre-op staff when you visit the hospital. When in doubt, please e-mail or call.

Should I take vitamins and supplements before surgery?

No, and these should be stopped around 10 days before surgery. Vitamins, herbal supplements, and nutrition supplements can interact with the other medicines we use during surgery, and can lead to excessive bleeding during and after surgery. After knee replacement, patients usually take a blood thinner for around a month. You can resume taking vitamins, supplements, and alternative therapies once you are off the blood thinner.

The Night Before Surgery

What do I need to do the evening before surgery?

The evening before surgery take a shower, but avoid shaving the legs, since this increases the bacterial load.

For your hospital stay, pack a bag with a robe or housecoat that opens in the front; house shoes or comfortable shoes for physical therapy; personal hygiene items; underclothing; glasses or contact lenses with case; dentures or partials with case; a case for hearing aid and spare battery; a walker if you have one; a C-Pap machine if you use one; loose fitting clothing to wear for physical therapy; advance directive if you have one; a list of current medications with dosages; an inhaler if you use one; and reading material, cell phone, and laptop computer if you prefer. The hospital has wireless Internet for your use.

Can I take my medicines the night before surgery?

You should take your blood pressure and heart medications with just a sip of water the morning of surgery. Your medical doctor may advise differently; if so, please follow his or her instructions and let the surgical team know. For example, in some patients, warfarin may be an essential medication safeguarding against stroke. In that case, your surgeon will work with the medical doctor to continue this drug, and alter their surgical preparation accordingly.

The pre-operative visit to the hospital is a good time to take notes and ask questions. Each patient is different; procedures and planning should be customized to your individual needs.

Why might surgery be cancelled at the last minute?

If you have an unexpected health problem, it may be safest to postpone the surgery until the situation is addressed. Let your doctor know if you have any of the following close to your scheduled surgery: symptoms of a cold or flu (chills, fever, or a cough); pain, burning or frequency when you urinate; cuts, scratches, rashes, bug bites, non-healing sores on your skin; new swelling on the leg undergoing surgery; or a change in your medical condition, such as high blood sugar or chest pain. These situations could mean that surgery has to be rescheduled.

Anatomy of the Knee

The knee joint is the mobile connection between the thigh bone (femur) and the shin bone (tibia). Cartilage lines the knee joint, and the moving surfaces are held together by strong ligaments and tendons.

The knee works roughly as a hinge joint, although actual knee movement and geometry are far more complex than a simple hinge. Knee motion involves rotation, sliding, and many other types of movement.

The joint lining (called synovium) secretes a grease-like liquid called synovial fluid, which reduces friction in the knee joint. This fluid is produced in other joints also, and it is the equivalent of biological “motor oil.” This oil-like fluid keeps the knee joint lubricated.

Day of Knee Surgery

What will happen on the day you’re having your knee operation?

You’re probably feeling nervous about your surgery!

Where will the surgery be done?

Of course it depends on the surgeon and medical team you’ve chosen. A good option is an advanced specialty orthopaedic hospitals and center.

Such centers are specifically equipped for joint replacement surgery and national data show a lower risk of complications, such as infections, and better outcomes from hip and knee replacement surgery at such specialized centers.

Your surgeon and medical team will offer you specific guidance and answer all your questions; please follow their instructions! The advice below is general; not every surgeon or hospital does things the same way.

What should I do the day of my surgery?

Remember not to eat or drink anything, including gum, candy, chewing tobacco, etc. Avoid make-up, nail polish on fingers or toes, perfume, or cologne. Remove all jewelry in anticipation of surgery.

Can I wear my contact lenses to surgery?

You will have to remove your contact lenses prior to going into the operating room. Bring glasses, if you have them, or bring solution and a holder for your contacts.

What type of anesthesia will I have?

Most surgeries are done using a spinal anesthetic with sedation. This type of anesthesia is safer than general anesthesia for knee replacement surgery. In addition, a combination of injections and pain pumps is common. If you have any preference for a certain kind of anesthetic, please let your medical team know.

Modern anesthetic drugs ensure that you will probably remember very little, if anything, about the surgery, and are developed to ensure your safety and comfort.

Where does my family wait and how will they know about surgery?

Your family will wait in a designated waiting room while you are in surgery. They will be informed when surgery is completed and you are in the recovery room. You will remain in the recovery room for approximately 1½ to 2 hours before going to your room. Your family can see you once you have arrived in your room.

How much will I hurt right after surgery?

Early pain is almost eliminated with modern pain medications and anesthetic techniques. Recovery from surgery is far more comfortable today than it was just a few years ago. Pain medications may be given through a fine catheter in your back, or may be injected close to the femoral nerve.

Pain medications may also be given in the form of a patient-controlled analgesic (PCA) which runs into the IV; you control the dosing. The knee joint itself and the tissues around it are injected with local pain-killing drugs.

If you have been taking narcotic drugs before surgery, pain control after surgery is usually more difficult since the body is already desensitized to the pain killers. In such cases, a higher dose of pain killers is often needed, and sometimes a combination of drugs.

Pain medicines can be given by mouth, intravenously, or by intramuscular injection. If you hurt, please let someone know; they want to minimize discomfort and customize the treatment for you.

By the time you leave the hospital, your pain will be properly controlled by an oral pain medication. Depending on the patient, such medications may be taken for several weeks to several months.

What can I expect right after surgery?

You will be monitored in the recovery room for an hour or two, and most patients are reasonably alert by this time.

You will notice a bulky dressing on your knee and an ice pack. This ice pack helps to control pain and swelling. You may also have a drain in the incision that looks like a plastic tube; this is removed within 24 to 48 hours. Expect a catheter in your bladder to keep urine drained; this is usually removed within 24 hours.

After an hour or so the nursing staff will take you to a private room on a floor that has expertise in caring for knee surgery patients. If your family plans to stay in the hospital room with you, please talk to your nurse so that arrangements can be made.

The nursing staff will coach you to take frequent deep breaths after surgery. You will have a breathing device to help with this. This is a plastic breathing exercise machine designed to prevent pneumonia and keep the lungs healthy.

You may have an overhead trapeze or lift on your bed to assist you in moving independently. This allows you to use your arms to move your body. Feel free to position your body in any way you want after knee surgery. The knee can be bent or straight after surgery, as you prefer. For the first night, it’s best to keep the leg slightly bent, on a pillow, since this reduces bleeding in the knee. The head of the bed can be in any position that you like.

You will have some sort of pump device squeezing your feet or legs to reduce the chance of a blood clot. You should exercise your calf and ankles regularly after surgery while you are awake. This will cut down the risk of a blood clot.

Right after surgery, avoid eating solid foods. It is better to start with liquids, and make sure that you can handle these before you progress to a full diet. Nausea is a very common side effect of modern pain medications.

Why are there foot pumps on my feet after surgery?

Mechanical foot pumps are used to squeeze the feet and ankles intermittently after surgery in order to help reduce the chances of a blood clot forming. These are useful while you will be in bed and resting. They are commonly used while you are in the hospital; you will not use them at home.

Will I have nausea and pain immediately after surgery?

Typically, patients have little to no pain, but nausea is more common. This nausea can come from the anesthetic drugs or from pain medicines and we can help control it by changing pain medicines and prescribing anti-nausea agents if necessary. If you have pain, nausea, or any other disagreeable sensation, let the nursing staff know. They are very knowledgeable in controlling such symptoms. Usually, an adjustment of medications is all that it takes.

Is there a risk of falling in the hospital?

Yes. A combination of unfamiliar surroundings, surgery on the leg, narcotic medications, nerve blocks used to control pain, and the effects of anesthetic drugs can increase the risk of falling.

To avoid a fall in the hospital and after discharge, use a walker when out of bed, even if you feel that the knee feels fine and will hold you up. If in doubt, ask the nurse or therapist for assistance.

Knee Surgery Techniques

What goes on during a knee surgery?

Here are typical procedures that may help you understand the procedure.

How do you attach the artificial knee to my bone?

Your orthopedic surgeon will probably use bone cement to do this. The majority of total knees are affixed with cement, although un-cemented designs are also used. Outcomes from both are very good. For young and active patients, cement-less total knees are usually preferred because of excellent fixation and durability. Living bone next to the prosthesis keeps the implants secured over time, whether or not cement is used. The choice of cemented versus un-cemented knee depends on many factors, such as patient age, knee deformity, status of ligaments, and the quality of bone.

Who does the actual surgery?

Although team members will assist, and resident physician or students may observe, you should expect that a competent orthopaedic surgeon will perform the entire operation.

Does the orthopedic surgeon replace my kneecap too?

In part, yes. On the underside your own kneecap (also called the patella) a thin layer of arthritic cartilage and bone is removed during surgery. In its place, surgeons affix a plastic kneecap to your own remaining kneecap. This new part functions just like your own kneecap. The front surface of the kneecap is your own bone; it is the underside of the kneecap that is lined with plastic.

Are knee ligaments removed during surgery?

Internal knee ligaments (anterior cruciate ligament and posterior cruciate ligament) are usually so worn out in arthritic knees that what remains of them is removed. The knee prosthesis itself is engineered to substitute for internal knee ligaments and stabilize the joint.

New knee designs, such as the CONFORMIS custom-knee that is built for each patient offer the benefit of preserving knee ligaments. New knee designs and materials are constantly being introduced.

The supporting ligaments outside the knee joint are usually preserved during replacement surgery. These external ligaments are called the medial collateral ligament (located to the inside the knee) and the lateral collateral ligament (located to the outside of the knee). These ligaments continue to function after knee replacement surgery. For severe deformity, arthritic destruction, or unusual cases, prosthetic designs can substitute for all knee ligaments, providing more stability when compared to routine total knee prosthesis.

Thus, even very unstable and deformed knee joints can be replaced successfully, allowing the patient to fully weight-bear immediately, without fear of the knee giving out, and without knee braces. The choice of implant is based on the individual case and amount of knee joint deformity, as well as surgical judgment.

Will my leg have a tourniquet on during surgery?

A thigh tourniquet is a device like a blood pressure cuff. It is placed on your thigh and inflated to let the surgeon operate more easily by cutting off the blood supply to the leg while the knee joint is open.

For convenience and out of habit, many surgeons in the United States do use a tourniquet for knee replacement surgery. It is worth asking him or her about. Tourniquets can lead to increased tissue trauma to the thigh muscles, which are squeezed hard for the entire duration of surgery, and a lack of oxygen to the entire leg during the operation. The result is pain, tissue damage, and delayed recovery.

Will the knee bleed more without a tourniquet?

Studies have shown no difference in blood loss during knee surgery done with or without a thigh tourniquet. Without a tourniquet, most blood loss occurs during the operation. If need be, this blood can be collected by a cell-saver device and given back to the patient. With a tourniquet squeezing the thigh, all the blood loss occurs after the tourniquet is let down and oxygen-deprived tissues get the blood flow restored. This blood is usually collected in a drain placed in the knee joint after surgery and discarded.

How does computer navigation help in knee replacement surgery?

Precise alignment of the bones during knee replacement is critical to the long-term performance of the joint replacement. Computer programs can help in such alignment of bones, and reduce the possibility of error. Beyond computer-assisted technology, robotic arms help position bone preparation guides very precisely, and optimize the result for each patient.

With the advent of the custom-made knee replacement by CONFORMIS (Boston, MA), the need for gender-specific knees, left versus right knees, race-specific knees, high-flex knees, computer navigation, robotic-assisted surgery, and other supportive technologies is entirely obsolete and a thing of the past. With a custom-designed knee replacement, the fit, fill, sizing, orientation, rotation, depth, shape, contours, geometry, flexibility, and instrumentation are all optimized for one particular knee, unique to the individual patient. These parameters are optimized to their theoretical extreme, such that surgeon-to-surgeon variability is minimized, thereby maximizing patient outcomes, recovery, safety, reliability, and quality. This technology is revolutionary and commonly used for total knee replacements. Added benefits are simplification of surgery, reduction in product inventory and complexity, and the reduced chance of error.

In the world of knee (and hip) replacement surgery of tomorrow, custom-built implants will increasingly become adopted as surgeons and hospitals see the efficiency and benefits of this technology, at no added cost, and little downside. That is why we preferred to build each knee implant on a custom basis, for each patient. No two people are alike, and that applies to the knee joints as well, providing the most compelling, logical, and reasonable rationale for a custom, patient-specific approach to knee replacement.

Ask your surgeon about the latest materials and procedures.

Life with an Artificial Knee

Once you have an artificial knee, what will be different? Here are answers to common questions.

How do I know if I have a metal allergy to the knee part?

Orthopaedic implants are made of alloys of cobalt-chrome and titanium that have been implanted in millions of patients over the past three decades. Allergies to solid metal alloys are sometimes speculated, but are rarely seen in practice. Most instances of a painful knee after replacement have to do with a problem related to the surgery, or possibly an infection. A true metal allergy is extremely rare, and seldom encountered in clinical medicine.

What will weather changes feel like in the knee?

Some patients report increased pain and stiffness, or can feel changes in the weather after knee surgery, especially with an artificial joint. These sensations are not common though, and usually will disappear over one to two years after surgery. For the first couple of years, the bone adapts and grows around the metal prosthesis, and this bone activity probably leads to increased sensitivity to weather and pressure changes that some patients can feel in their joints.

What do I need to know about future dental work and other surgery?

Because you have an artificial knee joint in place, you must take care to protect it from infection. The same applies to any artificial implant in your body. Before having dental work (teeth cleaning, fillings, extraction or root canals) or certain medical procedures (colonoscopy, biopsy, endoscopies, etc.), you must take an antibiotic.

The antibiotic will help prevent bacteria from getting into the blood stream and thus into your knee. The odds of this happening are very rare, but the antibiotic can reduce this already small risk.

For routine dental prophylaxis following knee replacement surgery, antibiotics are required for your lifetime after the surgery.

What antibiotics are used to protect the prosthetic knee joint if I have dental work?

Cephalexin and amoxicillin are antibiotics commonly prescribed before and after dental work. You may take azithromycin or clindamycin if you are allergic to amoxicillin. You also may take any antibiotic recommended by the American Heart Association.

What other situations will I need antibiotics for, after the knee replacement?

Antibiotics given for other medical procedures may vary. Contact your doctor for advice if there is any doubt. Keep in mind that it will be necessary for you to be treated with a full course of antibiotics if you develop an infection such as an abscessed tooth, pneumonia, bronchitis, and skin or urinary infections.

If you cut your foot, or have broken skin on the leg, or infection in a toenail after a knee replacement, seek medical attention immediately. Ignoring a festering sore means that there is a risk the bacteria could migrate to the knee implant, resulting in a serious deep infection, even though it happens rarely.

Will the knee set off a metal detector at the airport?

Most likely, it will. Tell airport personnel that you have an artificial joint prior to entering the metal detector. Metal detection sensitivity at airports is highly variable, and it is impossible to say if a certain detector will set off the equipment. Your doctor or nurse will supply you with an implant identification card that you can carry to prove that you have metal knee replacement parts.

Can I have a MRI scan after knee replacement?

Yes. MRI scans of other parts of your body are safe after knee replacement. Although some old MRI scanning equipment may not be compatible with your prosthesis, the majority of MRI scanning equipment today is safe and compatible with knee replacement parts. You may also have a CT scan of any part of your body after a knee replacement.

How will I know if my knee implants happen to be recalled?

In the extremely unlikely event of a recalled implant, you will be contacted by the company who made the device. All implants have lot numbers registered with the implant maker. This information is kept in your medical record. If you want a copy of your X-ray or exact implant type and model for your records, please ask your physician.

Rest assured that of the millions of artificial joints implanted each year, the incidence of recall is exceedingly rare. Implant companies monitor the performance of their products very carefully.

Is there a long-term risk of failure of knee implants?

No, the implants are engineered to withstand your body weight and activity level, but the moving parts of a knee replacement do wear over a period of several decades. A properly aligned knee replacement done by a competent, experienced surgeon will usually last the lifetime of most patients.

Subtle component malpositioning and suboptimal orientation can however compromise the lifespan of the implant. This is why the skill and expertise with which the knee is implanted in your body is a critical determinant of how long the knee will last and how well it will perform.

How many times can you replace a total knee?

With modern technology, cases that were considered hopeless a few years ago can undergo successful knee replacement surgery. Such complex knee replacements are done every week in our specialty practice, and are referred from all over. So, there is no hard and fast rule as to how many times a knee can be replaced. Knees that have had multiple operations may be missing structural bone support, muscle cover, and quadriceps support.

While doctors hope that you never need such complicated knee operations, it is possible to get patients mobile again in situations that would have resulted in an amputation in the past. This reflects advances in surgery techniques and related technology.

What if I receive conflicting advice and opinions from other people taking care of me in the hospital or during home health visits?

Your own surgeon is your best resource.

Parts and Materials for Knee Replacements

Are there different kinds of knee implants?

Yes. There are several different types of knee replacements. All of them are variations of the basic design introduced more than 30 years ago, which is called the “total condylar posterior stabilized knee.” The choice of implants depends on factors such as the status of ligaments and the amount of deformity in the knee. Usually, surgeons use a “high-flex” design that is safe for deep knee bending. The implants come in “gender-specific” versions engineered to match the knee anatomy of men and women. As new designs in total knee replacements are developed, we expect surgeons to adopt them only after carefully considering the advantages, safety, and scientific merits of such designs.

What brand of knee implants do you use?

For most knee replacements, a custom implant tailored to each patient is the best option. The company that makes these is Conformis (www.conformis.com). This technology is the best design as of this writing (2014.) We have also used the Zimmer brand of knee implants (www.zimmer.com, and www.pacewithlife.com)

(Note: No implant company pays Dr. Bal to promote or implant its products and no commercial entity has contributed, in any way, to the preparation of this guide.)

Can you show me the parts used in a total knee replacement?

Your surgeon should be able to show you actual parts and will probably have other materials such as animations or video that you can see.

What if I want a different brand of knee prosthesis?

New implants are sometimes hyped up by local surgeons and hospitals eager to get your business. Some of these newer designs are true improvements, while others are simply old designs with new packaging, gimmicks, and slick marketing. As a new design is introduced and marketed by the orthopaedic implant industry, we will present it with an unbiased discussion on this website.

If truly innovative implants are introduced, the odds are that I or some of my colleagues have been using them well before they are released to community orthopaedic surgeons. If you have an interest or preference for a particular type or brand of knee implant, please talk to your surgeon.

Can ceramic parts be used in knee replacements?

Yes. The advantage is the lower wear rate of ceramics when compared to metals. In the United States, ceramic knees are used on a limited basis since the Food and Drug Administration (FDA) has not approved them for general use. Several years ago, we conducted one of the few clinical trials in the country on ceramic knees.

Ceramic parts are useful in the rare cases of a true metal allergy in selected patients. Ceramic components will likely become more common in the future. At the time, ceramic materials in total knees are more common overseas. Balancing the very low wear rates of ceramics is the fact that we do not have enough scientific data from U.S. studies to support their routine use in total knee replacements as of yet.

Do you use the same model of knee implant for all knee replacements?

No. Each patient situation is unique, and the type of implant chosen depends on many patient variables, including age, gender, weight, bone dimensions, ligament condition, bone quality, anticipated activity level, and occupational history.

In older patients with weak and osteoporotic bone, for example, the best choice may be a cemented model supplemented by design features that will support external knee ligaments. On the other hand, for a healthy young person with physically demanding job, the ideal model may be an uncemented total knee design that allows as much bone preservation as possible.

In patients who have had knee replacement in the past and are in need of repeat surgery, it is often necessary to use more complex models, to reconstruct deficient and missing bone.

Are newer knee implants much different from old ones?

Yes. There are newer “high-flex” knee designs that allow greater safety during deep knee bending. There are also newer “gender-specific” total knees made to fit the anatomical differences in the knees of men and women. All knee replacement components that we used incorporate these modern design features.

Other variations in total knee implants include a ceramic “oxinium” surface, the “rotating-platform” knee, and other brands marketed by implant companies. Discuss this with your surgeon and medical team; they will help you make an informed choice.

Can I get a “golfer’s knee” implant?

As above, if you prefer one kind of implant over the other, ask your surgeon. Keep in mind that no knee implant is better suited for golf or any other sport. Participation in activities such as golf is equally possible, and equally easy with any of the competing knee designs out there, whether or not they claim to be a “golfer’s knee.”

What about a custom knee replacement made just for my leg?

One of the most exciting innovations when I was practicing is the concept of custom-manufacture of knee implants that are made specifically to each patient’s size and unique anatomy. CT or MRI imaging is used to determine the precise anatomy of the patient’s ankle, hip, and knee. These data are sent to a company called CONFORMIS (Boston, MA), where the metal and plastic pieces are custom-made for the patient in about 5-6 weeks, much like a tailor-made suit. The instruments used to implant the knee prosthesis are designed for a one-time use, specific to the patient, and are made of a biodegradable material. One neat package contains everything needed for the operation, and is unique for each knee joint, fitting only that one.

We used this in my practice beginning in 2013 and found it truly innovative, a meaningful step forward in knee replacement surgery. Our results showed earlier and easier recovery for the patient, and x-rays that are beautifully precise in terms of rotation, alignment, and sizing. This technology incorporates all of our knowledge and design understanding in knee replacement, worldwide. It increases patient safety, promotes quality and consistency, ensures precision and a perfect fit every time, and therefore has our full support.

(Please interpret this information in light of a conflict, in that Dr. Bal serveds as consultant surgeon for CONFORMIS, and was on a surgeon advisory and design team for this company. He did not receive any royalty or other payment to promote or implant CONFORMIS knee products, however, since the consulting activities concern other CONFORMIS technology platforms.)

Are there other implants that are used to treat knee arthritis?

In unusual cases of knee arthritis and in relatively young patients, a shim-like device called the uni-spacer may be used. This device acts like a spacer to separate the worn-out knee surfaces and keep them from grinding against each other. Very few patients meet the criteria for this type of surgery, and a uni-spacer is a temporary option, best reserved for very young patients with knee arthritis.

In what cases do you use human tissue for knee replacement?

In rare cases, cadaver tissue can be used for reconstruction of the extensor mechanism in selected knees. These are complex cases with previous trauma that has ruptured the quadriceps tendon in addition to causing arthritis of the knee. For the majority of knee replacements, no human tissue is ever needed.

How does the artificial knee joint get lubricated?

After a joint replacement, the artificial bearing gets its lubrication from synovial fluid, just like the natural knee joint. After surgery, the synovial lining re-forms and secretes synovial fluid. In cars, oil must be changed regularly, but in the body, synovial fluid is recycled by the cells. No external lubrication of the knee joint is ever necessary. In fact, any injections placed into your artificial knee joint increase the risk of infection.

Can patients become allergic to the knee replacement parts?

The metals used in artificial knees are alloys of cobalt-chromium and titanium. The bearing portion of the joint is made of a high-grade, wear-resistant plastic. The metal-plastic bearing combination is the most common type used in knee replacement implants worldwide. These metals have been used in humans for many decades and millions of patients with very successful results. Allergic reaction to artificial knee parts is virtually unheard of, and is not a routine clinical concern.

In the extremely rare case of a true metal allergy verified by testing, there are material science options to replace a knee without exposure to titanium, nickel, or cobalt-chrome, which are the usual metals used in standard knee replacements. In other words, metal-allergic patients can still get a knee replacement.

What actually moves inside an artificial knee joint?

In an artificial knee joint, highly polished cobalt-chromium metal moves against a very durable plastic spacer to allow movement. This bearing is lubricated by your body’s own synovial fluid, which is constantly replenished by living cells. The power to move the artificial knee, once implanted in your body, comes from your own muscles. That is why the condition of your muscles affects how quickly you recover after any type of knee surgery, including a total knee replacement.