Patient information: Total knee replacement (arthroplasty)

KNEE REPLACEMENT OVERVIEW

Total knee replacement, or total knee arthroplasty, is one of the most commonly performed orthopedic procedures. It is a surgical procedure in which parts of the knee joint that have been damaged, usually by a form of arthritis, are replaced with artificial parts (prostheses).

A normal knee functions as a hinge joint between the upper leg bone (femur) and lower leg bones (tibia and fibula) (figure 1). The knee joint has three compartments: lateral and medial, where the femur and tibia cartilage surfaces meet, and a patellofemoral surface between the kneecap and femur.

Damage to the cartilage in one or more compartments can be caused by various conditions, including osteoarthritis and inflammatory arthritis (eg, rheumatoid or psoriatic arthritis). Total knee replacement means replacing all three of the knee's compartments. For a review of the other treatment options available to patients with these types of arthritis, (see "Patient information: Osteoarthritis treatment" and "Patient information: Rheumatoid arthritis treatment" and "Patient information: Psoriatic arthritis".

REASONS FOR KNEE REPLACEMENT

Total knee replacement is an elective surgery. It is usually considered when other, non-surgical methods of treatment (ie, activity modification, weight loss, medications and injections) have failed to relieve arthritis-associated knee pain. Candidates for total knee replacement should also have x-ray evidence of advanced arthritic changes to the knee. Examples of patients who should not undergo the procedure include those with active infection in the knee or anywhere in the body, poor circulation, or neurologic disease affecting the extremity.

The goal of knee replacement is to relieve pain, improve the quality of life, and maintain or improve knee function. The procedure is performed on people of all ages, with the exception of children, whose bones are still growing.

ALTERNATIVES TP KNEE REPLACEMENT

While total knee replacement can be helpful under the right circumstances, the patient should recognize that it is an elective procedure. It should only be considered after a discussion of the risks, benefits, and alternatives with a healthcare provider.

Nonsurgical treatment — Nonsurgical treatment methods are initially recommended for patients with osteoarthritis or inflammatory arthritis.

Possible options for osteoarthritis include knee bracing and shoe inserts, both of which help align the knee and balance the weight load on the joint. Patients with rheumatoid or other inflammatory arthritis should have tried physical therapy, behavior modification, and drug therapy before considering total knee replacement. Injections, either with a cortisone-like drug or a hyaluronan derivative, are another form of treatment often attempted before considering surgery. (See "Patient information: Knee pain".)

Arthroscopy — Arthroscopy is a minimally invasive surgical procedure in which the affected joint is examined with a device called an arthroscope. Damage is repaired and debris removed through small surgical incisions in the skin. This treatment may be considered in certain cases, such as in patients with mechanical symptoms (locking, catching, or giving way of the knee joint).

Osteotomy — Osteotomy is a surgical approach in which a leg bone is cut, realigned, and allowed to heal. It is used to shift weight from a damaged compartment to a normal or less damaged one. It may be an option in younger patients whose knee damage is predominantly limited to the lateral or medial compartment. It is not recommended for patients older than 60 years or for those with inflammatory arthritis.

Unicompartmental knee replacement — A unicompartmental or "partial" knee replacement involves replacing only one compartment of the knee. This procedure may be beneficial for certain patients; however, it is the subject of some controversy. Supporters believe that preserving the normal ligament structure of the knee will allow the person to retain more natural knee movement; opponents feel that the procedure can lead to incomplete pain relief and increase the chance of loosening or wearing out of the plastic and metal knee replacement.

Patients who should not consider unicompartmental knee replacement include those with inflammatory arthritis, those who cannot bend the knee to 90 degrees, and those who are unable to fully straighten the knee (lack 15 degrees or more).

BEFORE KNEE REPLACEMENT SURGERY

Once a patient is determined to be a good candidate for total knee replacement, the healthcare provider will perform a preoperative evaluation, including a review of treatment alternatives and a discussion of autologous blood donation.

An autologous blood donation involves collecting the patient's own blood prior to surgery so that it can be used if a blood transfusion becomes necessary. It is safer than using donated blood as there is less risk of disease transmission or allergic reaction. (See "Patient information: Blood donation and transfusion".)

THE KNEE REPLACEMENT PROCEDURE

The procedure is performed in an operating room after the patient receives general, spinal, or epidural anesthesia. With general anesthesia, the patient is given medications through an intravenous injection and inhaled gas to induce sleep. The patient is unable to move or feel anything during the operation and will not remember the procedure afterwards.

Spinal and epidural anesthesia are forms of regional anesthesia in which an injection of anesthetic in the lower back temporarily blocks the feeling in the lower part of the body. With spinal anesthesia, the anesthetic is injected directly into the cerebrospinal fluid (CSF) surrounding the spinal cord; with epidural anesthesia, it is injected into the epidural space below the level of the spinal cord. The type of anesthesia used will depend on the particular patient's situation and is determined by the healthcare provider.

The patient is given antibiotics to reduce the risk of developing an infection. An incision is made to expose the inside of the knee joint. The bone and cartilage on the lower end of the femur (thigh bone) and upper end of the tibia (shin bone) are removed. The replacement (prosthetic) joint, usually made of metal and plastic, is then implanted.

The exact type of implant and the method and location of the incisions depend upon the needs of the particular patient and the surgeon performing the procedure. All total knee arthroplasties consist of a femoral component, a tibial component and a patellar component. There are many manufacturers and designs of knee prostheses. Most prostheses last at least 10 years; the prosthetic joint lasts longer in older, less active patients, and in patients with rheumatoid arthritis (as opposed to osteoarthritis).

After implantation, x-rays of the new prosthetic knee are taken (picture 1A-B). This allows the surgeon to confirm and document the correct placement of the joint; it can also be used to compare with future x-rays.

AFTER KNEE REPLACEMENT SURGERY

Management — Postoperative management includes controlling pain with intravenous or oral medication. Many joint replacement patients are given "patient-controlled analgesia". This gives pain medication through an intravenous line (IV) in the hand or arm. Patients are able to control, within preset limits, when a dose is given. Patients are also given an antibiotic (generally for 24 hours following surgery).

A blood-thinning medication such as low molecular weight heparin (Lovenox® or Fragmin®) or warfarin will be given to help prevent blood clots in the legs. Compression boots (devices that go around the legs and inflate periodically) or special support stockings are often used to aid in the prevention of blood clots. The support stockings are usually worn for several weeks following surgery.

Patients are encouraged to start moving the feet and ankles immediately after surgery. Some surgeons also recommend the use of a continuous passive motion (CPM) device, which elevates and slowly moves the leg while the patient is in bed. It is common to begin physical therapy, including exercise of the knee and trying to walk, as soon as one day after the procedure.

Rehabilitation — Physical therapy is an important part of the recovery process. Most patients spend three to five days in the hospital, during which they work with a physical therapist to develop an exercise and rehabilitation program. Some patients continue their therapy at home under the supervision of a physical therapist, while others may stay in a rehabilitation facility until they are able to perform daily activities independently.

The rehabilitation program generally includes: exercises to improve range of motion, gait training, thigh muscle (quadriceps) strengthening, and training in activities of daily life. The patient's goals and expectations are based on evaluation by and discussion with the physician and physical therapists.

Patients can usually resume their normal activities within three to six weeks following knee replacement. The goal of the rehabilitation period is regaining strength and motion; it is important to avoid overworking or straining the knee during this recovery period. After several months of rehabilitation, patients are encouraged to maintain an active lifestyle. While high-impact sports such as running or contact sports should be avoided, patients can typically participate in activities like walking, cycling, and swimming.

Potential complications — Complications are not common, and can usually be prevented with good surgical technique and careful post-operative management. However, it is important to consider the potential complications.

Studies have shown that a successful joint replacement partially depends upon the experience of the surgeon and the hospital. In one study, better outcomes were seen with surgeons who had performed more than six knee replacements each year, and in hospitals where more than 25 joint replacements were performed per year [1]. Specifically, post-operative knee function was better and rates of complications following surgery were lower. However, patient satisfaction and pain scores were not different in these patients compared to those who had their surgeries with less experienced teams.

Thus, there is some data to suggest that complication rates may be decreased by having the surgery done in a hospital that performs joint replacement surgery often and by a surgeon experienced in the procedure.

Thromboembolism — Inflammation, swelling, and lack of movement of the legs increase the risk of a blood clot forming in a vein (thrombosis). A blood clot that travels (embolus) can interfere with blood flow to the lungs. Pain and swelling, usually in the calf or the thigh following knee replacement, can be the result of a clot in a deep vein of the leg. Chest pain, shortness of breath, coughing up blood, or fainting are symptoms that suggest that the clot has traveled to the lung, causing embolism. Patients with symptoms of either thrombosis or embolism should speak with their healthcare provider as soon as possible.

Infection — Infection following knee replacement is a relatively uncommon but serious complication. Fever may indicate an infection; shaking chills, a sudden worsening of pain at the surgical site, increasing redness, or swelling are other features that suggest infection and need prompt medical attention.

Wound infections are treated with antibiotics, and occasionally by draining excess fluid from the affected area. If an infection becomes deep or extensive, the prosthetic joint may need to be removed and reimplanted later, after the infection has cleared.

Patellofemoral disorders — Potential patellofemoral complications include loosening, dislocation, fracture of the patella (kneecap), and rupture of the tendons attached to the patella. Treatment may require surgery in some situations. For more serious complications, the entire prosthesis may need to be replaced.

Nerve injury and sensory loss — The most common neurologic condition that occurs after total knee replacement is peroneal nerve palsy; symptoms include numbness, tingling, and weakness of muscles in the leg. If this occurs, the dressings should be loosened and the knee flexed (bent) to relieve pressure on the affected nerve.

SUMMARY

• Total knee replacement is a commonly performed surgical procedure that can benefit certain patients who have tried other, non-surgical treatment methods (including using knee braces or shoe inserts, as well as medication) without success. The surgery involves replacing all three of the knee's compartments (figure 1) with prosthetic (artificial) parts, with the goal of relieving pain and improving function.
• Most candidates for total replacement of the knee suffer from pain due to arthritis. (See 'Reasons for knee replacement' above.)
• A candidate for total knee replacement will be evaluated by a healthcare provider prior to surgery. This evaluation includes a review of the patient's symptoms and medical history, a physical examination, x-rays and laboratory tests, and a thorough discussion of the risks and benefits of the procedure as well as any alternate options. (See 'Before knee replacement surgery' above.)

• The patient is anesthetized (given drugs to temporarily prevent movement and pain) for the procedure, and given antibiotics to prevent infection. The surgeon makes a cut to expose the inside of the knee joint, and removes the bone and cartilage on the lower end of the femur (thigh bone) and upper end of the tibia. The replacement joint or prosthesis, typically made of metal and plastic, is then implanted. (See 'The knee replacement procedure' above.)

• Following surgery, the patient is given medications to prevent infection and control pain. Measures are also taken to prevent blood clots; these include taking blood-thinning medications and wearing compression devices and/or special support stockings on the legs. Some patients will also use a continuous passive motion (CPM) device, a machine that elevates and slowly moves the leg while the patient is in bed. (See 'Management' above.)

• The patient will work with a physical therapist after surgery to develop a rehabilitation program to strengthen the knee and regain movement.
• Patients can usually resume their normal activities within three to six weeks following knee replacement, and can participate in low-impact activities such as walking, cycling, and swimming after rehabilitation is completed.
• Complications following knee replacement surgery are uncommon, and can usually be prevented with careful post-operative management. (See 'Potential complications' above.)

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Osteoarthritis treatment
Patient information: Rheumatoid arthritis treatment
Patient information: Psoriatic arthritis
Patient information: Knee pain
Patient information: Blood donation and transfusion

Professional Level Information:
Complications of total knee arthroplasty
Low molecular weight heparin for venous thromboembolic disease
Pathogenesis, clinical manifestations, and diagnosis of prosthetic joint infections
Prevention of prosthetic joint infections
Prevention of venous thromboembolic disease in medical patients
Prevention of venous thromboembolic disease in surgical patients
Surgical therapy of osteoarthritis
Total joint replacement for severe rheumatoid arthritis
Total knee arthroplasty
Treatment of prosthetic joint infections

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• The Arthritis Foundation

      PO Box 19000
      Atlanta, GA 30325
      (800) 283-7800
      (www.arthritis.org)

• American Academy of Orthopaedic Surgeons

      (www.aaos.org)

UpToDate wishes to acknowledge Kelly Crowley for her contributions to this topic.

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