Informed Patient Tutorial
Copyright 2012 by the American Academy of Orthopaedic Surgeons

Informed Patient - Total Knee Replacement


Welcome to the American Academy of Orthopaedic Surgeons' Informed Patient Program. These online learning modules have been developed by orthopaedic surgeons to help you better understand your condition and the treatments your doctor recommends.

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Click the "Next" button to begin your learning module.

Total knee replacement is a safe and effective surgical procedure for relieving knee pain and restoring physical function in patients who are no longer helped by nonsurgical treatments.

According to the National Hospital Discharge Survey, more than 600,000 knee replacements are performed in the United States each year.

This learning module will explain why your knee may hurt and what treatments may be used to relieve the pain. It will review some of the causes of a painful knee and discuss nonsurgical treatment options.

It will then explain why a total knee replacement may be the best option for you, and what you can expect after surgery.

There are 10 parts to this learning module. As you work through them, you will be asked whether you understand the information, and you will be reminded to write down any questions you still have. This way, you will be able to bring your questions with you the next time you see your orthopaedic surgeon.

The learning module includes the following sections:

  • Your Knee: The anatomy of the knee is explained.
  • Causes: Many conditions cause a painful knee. This section describes some of the conditions that may lead to knee pain.
  • Symptoms: This section explains some of the signs to look for in a painful, osteoarthritic knee.
  • Diagnosis: This section explains some of the ways knee arthritis is diagnosed.
  • Nonsurgical Treatment: There are many nonsurgical options physicians have to treat osteoarthritis. Some of these are explained in this section.
  • Surgical Treatment: This section describes common surgical treatment options.
  • Your Total Knee Replacement Surgery: This section reviews what you may expect during total knee replacement surgery.
  • After Surgery: This section explains what you may expect after total knee replacement surgery.
  • Risks and Complications: Some risks and complications can be expected with any surgery. This section outlines some of the most common risks associated with total knee replacement surgery.
  • Conclusion: This section sums up the information and provides you with an opportunity to add more questions for your doctor.

Your Knee

Your knee is the largest joint in your body. It is a "hinge-type" joint made up of three bones: the femur (thighbone), tibia (shinbone), and the patella (kneecap).

The ends of these bones are covered with smooth white tissue called articular cartilage. This slippery surface helps your knee bones glide smoothly as you bend or straighten your leg.

The menisci are located between the tibia and femur. These C-shaped wedges act as "shock absorbers" and stabilize and cushion the joint.

Four ligaments in your knee act like strong ropes to hold the bones together, keep your knee stable, and allow it to bend. These are:

  • The medial collateral ligament (MCL)
  • The lateral collateral ligament (LCL)
  • The anterior cruciate ligament (ACL)
  • The posterior cruciate ligament (PCL)

Do You Understand?

Do you understand the anatomy of the knee?

Please take a moment now to write down any questions you still have about the anatomy of the knee.

Bring your questions to your orthopaedic surgeon at your next appointment.

Causes of Knee Pain

Many diseases can cause a painful knee. Some of these include:

  • Osteoarthritis
  • Rheumatoid arthritis
  • Post-traumatic arthritis
  • Gout
  • Avascular necrosis
  • Psoriatic arthritis


Osteoarthritis is the most common diagnosis for patients having total knee replacement.

It may be caused by advancing age, repetitive impact on a joint, or simple "wear and tear."

Osteoarthritis causes the cartilage that cushions the bones of the knee to wear away, exposing the bone.

Development of osteoarthritis.


When the cartilage wears away, the space between the femur and tibia narrows. This can result in bone rubbing on bone, and produce painful bone spurs and other deformities.

Osteoarthritis develops slowly. Once it occurs, your knee can become stiff and painful.

Unlike other forms of arthritis, osteoarthritis affects only one joint or a few joints at a time. It is a common problem for many people as they get older, and is a leading cause of disability in the United States.

Development of osteoarthritis.

Rheumatoid Arthritis

Rheumatoid arthritis is an autoimmune disease. This means that instead of protecting the joint, the immune system begins to produce substances that destroy the joint, as well as the ligaments, tendons, and muscles that support it.

Unlike osteoarthritis, rheumatoid arthritis affects many joints throughout the body at the same time. Multiple joints become swollen, painful, and stiff. The bone becomes soft and the joint surfaces break down.

Post-traumatic Arthritis

If a bone breaks within or near a joint, the joint surface may be damaged. An irregular joint surface can lead to arthritis in the joint years after the injury.

For example, here is an x-ray of a healthy knee with normal space between the bones, as shown by the arrow.

Post-traumatic Arthritis

Several months later, this patient fractured the tibia near the knee joint, shown by the blue arrows.

Post-traumatic Arthritis

The fracture was treated with a metal plate and screws. Two years after the injury, post-traumatic arthritis has developed in the knee. The joint space between the bones has narrowed, as shown by the red arrow.

Post-traumatic Arthritis

In addition to fractures around the knee, other injuries can result in arthritis. Because the menisci cushion the knee joint, damage to or removal of large portions of the menisci can lead to arthritis years later.

Similarly, chronic instability of the knee caused by ligament injuries can cause premature wear of the knee joint that results in arthritis.


Gout occurs when uric acid crystals form within a joint. These crystals cause inflammation and can cause the cartilage lining of the joint to wear away prematurely, resulting in arthritis.

In its early stages, medication can reduce the frequency and severity of gout attacks. An acute gout attack can cause severe pain and a warm, swollen, reddened knee.

Avascular Necrosis

Avascular necrosis (osteonecrosis) is a less common cause of knee pain.

In avascular necrosis, a segment of bone in the femur just above the knee loses its blood supply and begins to die.

This x-ray of the knee shows an area of the femur that has collapsed.

In most cases, the cause is unknown. It can, however, be associated with steroid use, obesity, and various diseases.

An x-ray showing avascular necrosis. Reproduced from Johnson TR, Steinbach LS, eds: Essentials of Musculoskeletal Imaging. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, p 544.

Avascular Necrosis

The caving in of bone due to avascular necrosis is very pronounced in this magnetic resonance imaging (MRI) scan. The abnormal bone has a whitish appearance and is shown by the arrows.

The onset of avascular necrosis is usually sudden. Symptoms start when small areas of bone immediately above the joint line collapse and the cartilage loosens. Early symptoms can be treated with rest and bracing. If the condition progresses, surgery, such as knee replacement, may be required to reduce pain.

An MRI showing avascular necrosis. Reproduced from Johnson TR, Steinbach LS, eds: Essentials of Musculoskeletal Imaging. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, p 544.

Do You Understand?

1. Do you understand the common causes of an arthritic knee?

2. Do you understand what your specific form of arthritis is?

Please take a moment now to write down any questions you still have about the causes of knee arthritis.

Bring your questions to your orthopaedic surgeon at your next appointment.

Symptoms of Knee Arthritis

The onset of symptoms in your knee may be gradual. The pain may come and go. It may occur only when you walk long distances, bend over, or climb stairs.

As the disease gets worse, you may notice pain when you are sitting, lying down, or even sleeping. The pain may last for longer periods of time and may not go away. Your knee may swell.

The most common symptoms of arthritis include:

  • Pain on the inside or outside of your knee or under your kneecap
  • Inability to fully straighten or bend your knee
  • Grinding sensation in your knee joint

The most common symptoms of arthritis include:

  • Pain on the inside or outside of your knee or under your kneecap
  • Inability to fully straighten or bend your knee
  • Grinding sensation in your knee joint
  • Your knees may become excessively bow-legged or knock-kneed

As the arthritis progresses, it may be hard to go up and down stairs or walk long distances. You may need to rest after walking for just a few minutes.

Do You Understand?

1. Do you understand the symptoms of an arthritic knee?

2. Do you have some or all of the symptoms of knee arthritis?

Please take a moment now to write down any questions you still have about the symptoms of knee arthritis.

Bring your questions to your orthopaedic surgeon at your next appointment.


Orthopaedic Evaluation

An evaluation by an orthopaedic surgeon consists of several components.

Medical history

Your orthopaedic surgeon will gather information about your general health and ask about the extent of your knee pain and your ability to function.

Orthopaedic Evaluation

Physical examination

This will assess your knee motion, stability, strength, and overall alignment of your leg.

Orthopaedic Evaluation


These images help to determine the extent of damage and deformity in your knee.

In the x-ray on the right, arthritis has caused decreased joint space with bone touching bone.

Other tests

Occasionally, blood tests, a magnetic resonance imaging (MRI) scan, a computed tomography (CT) scan, or a bone scan may be needed to determine the condition of the bone and soft tissues of your knee.

Orthopaedic Evaluation

Your orthopaedic surgeon will review the results of your evaluation with you and discuss the best treatment options to relieve your pain and improve your function. Both nonsurgical and surgical options may be discussed and considered.

Do You Understand?

Do you understand how your orthopaedic surgeon evaluates your condition?

Please take a moment now to write down any questions you still have about the orthopaedic evaluation.

Bring your questions to your orthopaedic surgeon at your next appointment.

Nonsurgical Treatment

There are many ways to treat an arthritic knee without surgery. These include:

  • Activity changes
  • Medications
  • Weight loss and exercise
  • Walking aids and braces
  • Injections

Activity Changes

First, you should limit or change the activities that make your knee hurt.

You may want to stop and rest if you are walking long distances. You may want to avoid bending and lifting.

Activity Changes

You can limit exercise activities that have a heavy impact on your knee, such as running. Walking, swimming, and bicycling are good, low-impact exercise options.

You can also shorten the duration of your sports activities. For example, take a quick half hour walk rather than spend an hour on the treadmill.


Non-steroidal anti-inflammatory medications, or NSAIDs, may help to control your symptoms. Some examples of NSAIDs are aspirin, ibuprofen, and naproxen.

These may be taken on a regular basis or only when you have pain. They can, however, have side effects, such as nausea, stomach upset, or bleeding.

It is important to see your doctor on a regular basis if you are taking any of these drugs.


Over-the-counter supplements like glucosamine and chondroitin sulfate may help relieve pain for some people.

Talk to your doctor before using any supplements.

Weight Loss and Exercise

If you are overweight, you may reduce the stress on your knee and relieve some of the pain by losing weight.

Regular exercise or physical therapy can help strengthen the muscles that support your knee, and preserve the motion in your knee. This can prevent stiffness and allow you to do more.

Walking Aides

A walking aid, such as a cane, can provide support and balance. You will probably feel more comfortable holding the cane in the hand opposite the side of your bad knee.

Occasionally, bracing may be helpful in controlling the symptoms of knee arthritis.


There are two types of injections that may ease the pain of knee arthritis: cortisone injections and viscosupplementation.

Cortisone is a steroid that is naturally produced in your body. It is a powerful anti-inflammatory medicine that is injected directly into your knee joint. Injectable cortisone is synthetically produced and designed to last longer than natural cortisone. It reduces pain and inflammation and can be used for short-term control of knee discomfort.

Viscosupplementation is a procedure in which hyaluronic acid is injected into the knee joint. Hyaluronic acid is a lubricant found in healthy knees. Injections are typically done 1 to 5 times over several weeks, and may provide relief of arthritis symptoms for several months.

Cortisone injection

Do You Understand?

Do you understand the ways to treat a painful knee without surgery?

Have you tried some or all of the nonsurgical options?

Please take a moment now to write down any questions you still have about nonsurgical treatments.

Bring your questions to your orthopaedic surgeon at your next appointment.

Surgical Treatment

There are several common surgical options available to treat arthritis of the knee.

These include:

  • Arthroscopy
  • Osteotomy
  • Partial knee replacement
  • Total knee replacement


During arthroscopy, doctors use small incisions and thin instruments to diagnose and treat joint problems.

Arthroscopic surgery is not often used to treat arthritis of the knee. Although it is valuable in removing loose fragments of bone, cartilage, or torn meniscus, arthroscopic surgery cannot repair large areas of arthritis or correct deformities or stiffness.


In an osteotomy, the bones around the knee are cut and realigned to take pressure off of the painful part of the knee joint. An osteotomy can correct deformities caused by arthritis or previous injuries. These procedures are most commonly performed to realign a bowed knee.

The illustration shows a tibial osteotomy. A wedge of bone is removed to straighten out the leg. Afterward, the tibia may be held in place with a plate and screws.

Osteotomies are most helpful for knees where only one area, typically the inner side of the knee, is damaged. They are typically performed in younger patients who have limited arthritis and wish to return to high activity levels.

Tibial osteotomy

Partial Knee Replacement

A unicondylar replacement (UKR), commonly referred to as a partial knee replacement, is an alternative to total knee replacement for a select number of patients. Partial knee replacements are used when only one compartment, or area of the knee, is damaged.

Because a partial knee replacement is done through a smaller, less invasive incision, hospitalization is shorter, and rehabilitation and return to normal activities is faster.

Although UKRs have recently grown in popularity, only about eight out of 100 patients with arthritic knees are good candidates for the procedure.

Total Knee Replacement

Total knee replacement (TKR) is the most common surgical procedure used to treat a patient with an arthritic knee.

Most patients who undergo total knee replacement are aged 60 to 80, but orthopaedic surgeons evaluate patients individually. Recommendations for surgery are based on a patient's pain and disability, not age. Total knee replacements have been successfully performed at all ages, from the teenager with juvenile arthritis to the elderly patient with degenerative arthritis.

Total Knee Replacement

In most cases, a total knee replacement becomes the best option when your arthritic knee causes so much pain that it interferes with your overall quality of life. For many patients, this means that the arthritis pain limits walking, standing, climbing stairs, or interferes with sleep.

Such severe arthritis can be seen in the x-ray on the left. Note that cartilage damage has decreased the joint space between the femur and tibia. On the right is a total knee replacement as it appears in an x-ray.

While knee replacements are very successful, there is rarely an emergency need to have the surgery. Remember, there is no risk to not having surgery other than that your quality of life may suffer.

X-rays of severe osteoarthritis (left) and a total knee replacement (right)

Do You Understand?

Do you understand the different surgical options for treating knee arthritis?

If your doctor has recommended a surgical procedure for your arthritis, do you understand why?

Please take a moment now to write down any questions you still have about surgery for arthritis of the knee.

Bring your questions to your orthopaedic surgeon at your next appointment.

Your Total Knee Replacement Surgery

Before Surgery

Your orthopaedic surgeon will help you plan and prepare for your surgery. You may have to obtain tests such as blood tests, an electrocardiogram (ECG), or chest x-ray.

Be sure you have discussed your entire medical history with your surgeon, and have provided any medications you are taking.

Your orthopedic surgeon may ask you to make an appointment with your primary doctor to make sure that you are healthy enough to proceed with surgery.

Before Surgery

To reduce the risk of infection, any dental problems or urinary or sinus infections must be treated before surgery.

You may be asked to donate your own blood in case you need a blood transfusion after the procedure.

Before Surgery

Being physically ready for surgery can reduce your recovery time. Many patients begin physical therapy before surgery. Practicing exercises beforehand can make it easier to do them after surgery.

The Day of Surgery

Most patients are admitted to the hospital on the day of surgery.

The Day of Surgery

Before your procedure, an anesthesiologist will evaluate you. Your anesthesiologist will review your medical history and discuss anesthesia choices with you.

Anesthesia can be either general (in which you are put to sleep), or it can be spinal, epidural, or regional nerve block anesthesia (in which you are awake but your body is numb from the waist down). The anesthesia team, with your input, will determine which type of anesthesia will be best for you.

Do You Understand?

Do you understand what you may need to do before surgery?

Do you understand the different anesthesia options?

Please take a moment now to write down any questions you still have about what happens before surgery.

Bring your questions to your orthopaedic surgeon at your next appointment.

The Procedure

Total knee replacement typically takes between 1 and 2 hours. Your surgeon will begin the procedure by making a vertical incision along the front of your knee.

After making the incision, your surgeon will remove damaged bone and cartilage, and prepare the ends of your bones for the artificial implant.

Newer techniques allow a total knee replacement to be done through smaller, minimally invasive incisions or using a computer to align the artificial implant with the bones. The long-term results of computer-assisted or minimally invasive procedures are not yet known.

The Procedure

While there are many types of implant designs with different materials used, all artificial knee devices consist of three components:

  • The femoral component, made of a highly polished strong metal
  • The tibial component, made of a durable plastic usually held in a metal tray
  • The patellar component, which is also made of plastic.

The metal is typically a metal alloy of cobalt, chrome, and molybdenum or titanium. The plastic is a long-lasting material called polyethylene.

The Procedure

The implant components come in a range of sizes in order to fit the femur, tibia, or patella.

If your posterior cruciate ligament is healthy enough to continue stabilizing your knee joint, your surgeon may use a cruciate-retaining component, shown on the left. A posterior-stabilized component like the one on the right is used if the ligament is removed.

(Left) A cruciate-retaining component. (Right) A posterior-stabilized component.

The Procedure

Your surgeon will position the metal and plastic implants to the joint surfaces. Strong cement may be used to hold the components to the bone.

Some implants have surfaces with a porous coating that allows bone to grow into the metal and hold the components in place.

Do You Understand?

Do you understand the different components of the knee implant?

Do you understand the surgical procedure?

Please take a moment now to write down any questions you still have about the procedure.

Bring your questions to your orthopaedic surgeon at your next appointment.

After Surgery

After surgery, you will be admitted to a hospital room, monitored, and given pain medicine. You will be given antibiotics to protect your knee from infection.

Your surgeon may prescribe measures to prevent blood clots from forming in your leg veins. These measures may include blood thinners, support stockings, or sequentially inflated devices (compression boots).

Physical Therapy

Physical therapy will be started on the day of surgery or 1 to 2 days after.

A physical therapist will teach you how to use a walker or crutches, and give you exercises to strengthen and gain motion in your knee.

Physical Therapy

Your surgeon may use a continuous passive motion machine to restore movement in your knee and leg. The device decreases leg swelling by elevating your leg and improves your circulation by moving the muscles of your leg.

A continuous passive motion machine.

Physical Therapy

After a short stay in the hospital, you will either go home or to a rehabilitation center.

You may be given assistive devices to help you put on your shoes or pick up objects from the floor.

Once you leave the hospital, you will have outpatient physical therapy. It is important to make a strong effort at exercise and rehabilitation in order to achieve a good result. Complete rehabilitation may take 2 to 4 months. Improvement may be seen for up to a year.

Do You Understand?

Do you understand what may happen in the hospital after surgery?

Do you understand how physical therapy will help you recover from surgery?

Please take a moment now to write down any questions you still have about recovering from surgery.

Bring your questions to your orthopaedic surgeon at your next appointment.

Risks and Complications

The complication rate for total knee replacement surgery is low. Most problems are minor and can be easily treated. Major complications occur in less than 2% of cases.

It is important that you know and understand the risks before you make a decision to have surgery. Possible surgical complications include:

  • Infection
  • Blood clots
  • Loosening of implant
  • Stiffness
  • Continued pain
  • Neurovascular injury


You will be given antibiotics before the start of your surgery and these will be continued for about 24 hours afterward. This is done to help prevent infection. A superficial infection may involve only the skin and soft tissues. A deeper infection may enter the knee joint and bone.

Infections can occur right after surgery or years later if bacteria enter the bloodstream from another part of your body. For this reason, it is recommended that you take antibiotics before you have any dental procedure. Check with your orthopaedic surgeon for specific recommendations about antibiotics and dental work.


You should also take antibiotics if you have an open wound, are having surgery, or have an infection in any other part of your body.

Many infections can be treated with antibiotics. A deep infection, however, may require a procedure to remove all of the knee replacement components. This would be followed by antibiotic treatment, and then a second surgery to implant a new knee joint.

Blood Clots

Blood clots in the leg veins are the most common complication of knee replacement surgery. Blood clots can form in the deep veins of the legs or pelvis after surgery. Blood thinners such as warfarin (Coumadin), low-molecular-weight heparin, aspirin, or other drugs may help to prevent this problem. Other measures, such as compression stockings, or pneumatic boots are also used to help prevent clots.

Clots are most likely to form in the first four weeks after surgery.

Blood Clots

Signs of a clot include unexplained pain, swelling, and redness in one or both legs.

In some cases, clots do not cause any symptoms. If your surgeon suspects a clot, he or she will order a special test called an ultrasound. If the test is positive, you may need to stay on blood thinners for several months.

Although rare, a clot may travel from the legs to another area of the body, such as the lungs. A clot that travels to the lungs is called a pulmonary embolism. This is a rare but potentially life-threatening complication, and requires immediate medical attention.


Loosening and Wear

Most total knee replacements will last for many years. Over time, however, the plastic surface of the tibia may begin to wear. This may cause the knee replacement to become painful or loose.

Loosening is most often due to everyday wear and activity. It can also result from a biologic thinning of the bone called osteolysis.

If significant wear occurs, a second surgical procedure, called a "revision" may be necessary. Revision implant components usually have longer stems that insert further into the bones.

New techniques and materials have been introduced that help reduce the incidence of loosening and wear, and prolong the durability of modern knee replacements.

Revision implants


Knee stiffness is a possible complication after surgery. Early and aggressive physical therapy is used to prevent post-operative stiffness.

The most common causes of stiffness are:

  • Multiple previous surgeries
  • Significant preoperative stiffness
  • Bleeding
  • Infection


In addition to physical therapy to overcome a stiff total knee, your doctor may recommend a continuous passive motion machine.

He or she may also perform a knee manipulation. In this procedure, you are put under anesthesia while your doctor moves and manipulates your total knee to break up scar tissue and gain mobility.

A continuous passive motion machine.

Continued Pain

A very small percentage of patients may continue to have knee pain after knee replacement surgery.

If the cause of the continued pain can be identified by your surgeon, he or she may recommend a revision surgery to fix the problem.

In rare instances, the cause of continued pain cannot be determined, and may be related to scar tissue that forms inside the knee. Fortunately, this is rare, and the vast majority of patients experience excellent pain relief following knee replacement.

Neurovascular Injury

Injuries to the nerves and arteries during total knee replacement are very rare. The most common arterial injury is to the popliteal artery, which is located immediately behind the knee. This artery can be injured when the knee is exposed for the surgery. In addition, injuries to the inner wall of this artery can occur due to pre-existing arteriosclerosis.

The most common nerve to be injured is the peroneal nerve, which runs behind the fibula. Although uncommon, a stretch injury to this nerve can cause weakness of the ankle or numbness in the foot.

Do You Understand?

Do you understand the risks and complications of total knee replacement surgery?

Do you understand the options for preventing blood clots after surgery?

Please take a moment now to write down any questions you still have about the risks and complications of surgery.

Bring your questions to your orthopaedic surgeon at your next appointment.



Total knee replacement is a highly successful procedure that can relieve pain in your knee and improve your mobility.

Your knee will most likely bend more than it did before surgery, but you may not regain full range of motion.


Most patients can expect to almost fully straighten the replaced knee and to bend the knee sufficiently to climb stairs and get in and out of a car. You may feel stiffness, particularly with excessive bending activities. Kneeling may be uncomfortable, but it is not harmful. It is not unusual to feel a soft clicking of the metal and plastic as you are bending or walking on your new knee.

These differences often diminish with time and most patients find them to be tolerable when compared with the pain and limited function they experienced prior to surgery.

It is important to understand the goals and limitations of knee replacement surgery, as well as the benefits and risks before making the decision to have surgery.

Your orthopedic surgeon is a highly trained specialist who can answer your questions and provide more information about knee replacement surgery.

If you have further questions about your upcoming surgery, take time now to write them down so that you can discuss them with your orthopaedic surgeon.

Related Topics

For more information about total knee replacement and surgery:

  • Arthritis of the Knee (http://orthoinfo.aaos.org
  • Preparing for Joint Replacement Surgery (http://orthoinfo.aaos.org
  • Total Joint Replacement: Questions Patients Should Ask Their Surgeons (http://orthoinfo.aaos.org
  • Total Knee Replacement (http://orthoinfo.aaos.org
  • Total Knee Replacement Exercise Guide (http://orthoinfo.aaos.org
  • Knee Implants (http://orthoinfo.aaos.org
  • Cemented and Cementless Knee Replacement (http://orthoinfo.aaos.org
  • Unicompartmental Knee Replacement (http://orthoinfo.aaos.org
  • Minimally Invasive Total Knee Replacement (http://orthoinfo.aaos.org
  • Activities After a Knee Replacement (http://orthoinfo.aaos.org
  • Deep Vein Thrombosis (http://orthoinfo.aaos.org

For more information on musculoskeletal health, return to the AAOS OrthoInfo (http://orthoinfo.aaos.org website.