Total knee arthroplasty

INTRODUCTION — Total knee arthroplasty (TKA), also known as total knee replacement, is one of the most performed orthopedic procedures. As of 2010, over 600,000 TKAs were being performed annually in the United States and were increasingly common [1]. Among older patients in the United States, the per capita number of primary TKAs doubled from 1991 to 2010 (from 31 to 62 per 10,000 Medicare enrollees annually) [2]. The number of TKAs performed annually in the United States is expected to increase in volume by 143 percent by 2050 compared with 2012 [3,4].

TKA consists of resection of the diseased articular surfaces of the knee, followed by resurfacing with metal and polyethylene prosthetic components [5]. For the properly selected patient, the procedure results in significant pain relief, as well as improved function and quality of life. In spite of the potential benefits of TKA, TKA is usually performed on an elective basis and should only be considered after exhaustion of appropriate nonsurgical therapies and extensive discussion of the risks, benefits, and alternatives.

This topic reviews aspects of TKA including indications and perioperative considerations. As with any major surgical procedure, complications may result during or after TKA. Complications of this procedure are discussed separately. (See "Complications of total knee arthroplasty".)

PREOPERATIVE CONSIDERATIONS

Indications — Generally, total knee arthroplasty (TKA) is performed for destruction of joint cartilage either from osteoarthritis, rheumatoid arthritis/inflammatory arthritis, posttraumatic degenerative joint disease, or osteonecrosis/joint collapse with cartilage destruction. Damage to the synovial joint of one or more of the three compartments (lateral, medial, patellofemoral) may be the result of a variety of pathologic conditions. Such damage causes pain and impairs the normal functioning of the knee joint, which is a complex hinge, primarily allowing flexion and extension but also allowing rotation and gliding.

●Osteoarthritis – Osteoarthritis is the most common type of arthritis in adults and can result in degenerative changes in the knee joint. Over 95 percent of TKAs in the United States are performed for osteoarthritis (picture 1) [1,6]. In patients with osteoarthritis, TKA is indicated for the relief of severe knee pain that is refractory to nonoperative treatments. Before proceeding to TKA, a multifaceted regimen of nonoperative treatment should be tried. Nonsurgical treatments offer significant benefit with lower risk. The efficacy of these nonsurgical interventions, even with advanced osteoarthritis, has been supported in clinical trials [7,8] and are appropriate, particularly in patients looking to avoid or postpone surgical intervention or for patients not fit for surgery. (See "Management of knee osteoarthritis", section on 'Moderate/severe knee osteoarthritis' and "Management of moderate to severe knee osteoarthritis", section on 'Surgery' and 'Medical risk assessment' below.)

●Inflammatory arthritis – Rheumatoid arthritis, gout, psoriatic arthritis, and spondyloarthritis, as well as other inflammatory arthritides, can all result in knee joint destruction and the need for TKA. However, the need for TKA due to inflammatory arthritis has declined due to the introduction of disease-modifying antirheumatic drugs [9,10]. (See "General principles and overview of management of rheumatoid arthritis in adults" and "Evaluation and medical management of end-stage rheumatoid arthritis" and "Surgical management of end-stage rheumatoid arthritis", section on 'Knee'.)

●Others – Other indications for TKA include posttraumatic arthritis (eg, following sports-related injuries, motor vehicle accidents), sequelae of infection, tumor, avascular necrosis (osteonecrosis), or congenital joint abnormalities.

Intraarticular infection resulting from bacterial, viral, or fungal organisms spreading through the bloodstream and depositing in the knee joint, penetrating trauma, or following knee surgery can cause septic arthritis. Subsequent damage to the articular cartilage can then result in debilitating joint pain and stiffness, which may require arthroplasty after proving infection has been eradicated with appropriate preoperative testing. (See "Septic arthritis in adults".)

Bone tumor involving the knee, either primary or metastatic, sometimes requires arthroplasty of the knee. Reconstruction can include the use of larger implants called megaprostheses (eg, total femur replacement, proximal tibia replacement) as part of limb salvage surgery.

Another possible indication for knee arthroplasty is avascular necrosis or spontaneous osteonecrosis of the knee (SONK), which is a condition of unknown etiology that results in an alteration to the blood supply of the knee, resulting in bone death and subchondral bone collapse and subsequent secondary osteoarthritis. (See "Treatment of nontraumatic hip osteonecrosis (avascular necrosis of the femoral head) in adults" and "Chronic complications and age-related comorbidities in people with hemophilia", section on 'Arthropathy' and "Overview of the musculoskeletal complications of diabetes mellitus".)

Contraindications — TKA should not be performed in the following clinical settings:

●Active infection – Active infection in the knee or anywhere in the body. TKA following infection that has been treated successfully must be undertaken with extreme caution. The risk of reactivation of quiescent infection or secondary infection following TKA is difficult to assess. Appropriate timing of arthroplasty after treatment of any infection is not well established, but it is prudent to delay until demonstrated to be infection-free off antibiotics. There may be up to a one-year delay between the treatment of septic arthritis and performance of TKA. Preoperative assessment may include evaluation of serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), joint aspiration, and imaging modalities such as magnetic resonance imaging (MRI) or bone scan to look for signs of persistent infection or osteomyelitis. (See "Nonvertebral osteomyelitis in adults: Clinical manifestations and diagnosis".)

●Nonfunctioning extensor mechanism – Neurologic disease affecting the lower extremity is a relative contraindication to TKA, depending upon the impact of the neurologic disorder on the potential for successful rehabilitation and for improvements in pain and function.

●Chronic lower extremity ischemia – In a patient with chronic lower-extremity ischemia, a thorough vascular assessment should be performed before undergoing TKA. The extent of large- or small-vessel disease, as well as the presence or absence of collateral flow, will influence the decision to proceed with revascularization procedures before TKA.

●Skeletal immaturity – Given that the physes near the knee are the major source of growth for the lower extremity, TKA is delayed until skeletal maturity is achieved.

It is important to note that patient participation in any type of postoperative rehabilitation program (eg, monitored or independent) is essential for a successful outcome following TKA, and an inability to participate may constitute a relative contraindication to this form of treatment. (See 'Rehabilitation' below.)

Surgical alternatives to total knee arthroplasty — The suitability of surgical approaches other than TKA, such as osteotomy, joint resurfacing, and unicompartmental arthroplasty, should be discussed with the patient. The various options depend on several factors, including the severity of the disease (eg, early chondral changes with minimal loss of joint space); the extent and location of disease, including whether it is unicompartmental (lateral, medial, or patellofemoral) versus bi- or tricompartmental; the disease process causing joint pathology (eg, osteoarthritis, rheumatoid arthritis, psoriatic arthritis, etc); and the patient's preferences for the risks and advantages associated with each option. (See "Overview of surgical therapy of knee and hip osteoarthritis", section on 'Alternatives to total knee arthroplasty'.)

PREOPERATIVE EVALUATION — Assessment of operative risk prior to total knee arthroplasty (TKA) includes verifying the severity of the underlying knee pathology and the failure of nonsurgical treatments, as well as identifying any medical comorbidities that might impact the choice of anesthesia, the conduct of the operation, and possible complications. The majority of TKAs are performed under elective circumstances for which there is adequate time to consider alternative treatments, assess surgical risk, and to make any necessary adjustments to medications.

Physical assessment — The patient's symptoms should be documented. It is critical to document and investigate any history of concomitant back pain (often described as hip pain by the patient), hip pain (often described as groin pain by the patient), or numbness, paresthesia, or pain in the leg. The presence of back or hip symptoms may indicate that knee pain is referred from these sites; neurologic complaints can arise from peripheral nerve, nerve root, or central nervous system disorders. The clinician must also inquire about calf pain or claudication, which could indicate peripheral vascular disease or spinal stenosis.

The location of the pain (eg, medial, lateral, or patellofemoral) and the severity of the pain and the effect of the pain on the patient's activities of daily living and quality of life should be documented. Aggravating and relieving factors should be elicited.

Previous interventions for the knee pain and their effectiveness (eg, weight loss, nonsteroidal antiinflammatory drugs [NSAIDs], glucocorticoid injections, hyaluronan injections, physical therapy [PT], alternative treatments, surgery) should be noted. Identifying patients with higher levels of pain, anxiety, and depression on validated pain scales and psychological health testing has been advocated. Patients who used opioids prior to TKA can experience less pain relief from the operation and may need more pain medication after surgery [11]. As such, preoperative optimization should target opioid reduction using multimodal strategies. (See 'Perioperative pain control' below.)

The physical examination should include the following:

●Comprehensive knee examination – The knee exam involves assessment of the extensor mechanism, range of motion, and stability/integrity of ligaments and should document the following preoperatively, which serve as a baseline to judge the success of the procedure and for comparison in the event of complications (see "Physical examination of the knee"):

•Range of motion – Maximal active and passive knee flexion and extension should be recorded and any joint contracture noted.

•Presence of crepitus and pain on loading of compartments – In addition to the detection of crepitus, pain in the patellofemoral, medial, or lateral joint with passive flexion/extension can also help the clinician determine the extent of the disease in each compartment.

•Ligament examination – Preoperative assessment of the stability or degree of contracture of the knee ligaments, including the collateral and cruciate ligaments, is important (figure 1 and picture 2). Evidence of collateral ligament incompetence may indicate the need for a more constrained prosthesis. The posterior cruciate ligament (PCL) may be retained or sacrificed at the time of surgery. The anterior cruciate ligament (ACL) is sacrificed in the majority of total knee replacement designs, and therefore its assessment is not considered to be important for most implants.

●Spine and hip examination – It is important to exclude referred pain to the knee originating from the spine or hip. Elicitation of the knee pain with straight leg raising or with hip motion (especially internal rotation) should raise suspicion and warrants further study including imaging of the lumbar spine, hip, or both.

●Neuromuscular evaluation – Motor strength and tone should be tested in the entire lower extremity with special attention devoted to the quadriceps or extensor mechanism. In addition to checking motor strength, sensory and deep tendon reflex assessments (patella and ankle jerks) should be performed.

●Gait – Observing the patient's gait pattern is an important part of the physical examination. Among the abnormal gaits that may be observed in patients with knee pain are the following.

•Antalgic gait – Patients with knee arthritis will often have an antalgic gait. The patient with an antalgic gait spends a shorter time bearing weight on the affected side because of pain.

•Knee thrust – An abnormal medial or lateral movement of the knee while walking (thrust) is usually associated with a varus or valgus (picture 3) deformity.

•Trendelenburg gait – With a Trendelenburg gait, the patient shifts the torso over the affected hip, reducing the load on the hip that is imposed by stabilizing the pelvis and thereby decreasing pain. This suggests the presence of hip joint disease and/or weakness of the gluteus medius muscle. In a patient with a Trendelenburg gait or test that is positive, hip or back pathology must be excluded before TKA is considered.

●Pulses – Distal pulses, including the dorsalis pedis and posterior tibialis, should also be assessed.

●Skin – The skin over both of the entire lower extremities should be thoroughly inspected for any abrasions, ulcerations, swelling, redness, vascular changes, or infections. TKA is contraindicated in the presence of an active infection. Any previous scars over the knee should be noted. Wound healing problems are common around the knee, and previous incisions need to be taken into account at the time of surgery. Any gross deformities (eg, varus, valgus, recurvatum, flexion contracture) should be noted. Deformities will be definitively assessed with radiographs.

Medical risk assessment — The patient undergoing TKA must be able to tolerate anesthesia, associated operative stress, and perioperative blood loss, as well as the rehabilitation process involved following TKA. Since many patients presenting as candidates for total knee replacement are older, specific attention should be paid to the patient's comorbid medical problems and symptoms that may reflect underlying comorbidities that need to be considered prior to undergoing TKA.

●Medical problems – Communication between the patient's primary medical provider and the surgeon or anesthesiologist is paramount. Any history of cardiovascular disease (eg, angina, myocardial infarction, hypertension, congestive heart failure, arrhythmia) or pulmonary disease (chronic obstructive pulmonary disease, restrictive lung disease, respiratory infection, pulmonary embolus, sleep apnea, asthma) should be investigated thoroughly. (See "Evaluation of cardiac risk prior to noncardiac surgery" and "Evaluation of perioperative pulmonary risk".)

●Review of systems – Other particularly important components of the review of systems include those indicating the possible presence of cerebrovascular disease (transient ischemic attacks, stroke, carotid stenosis), thromboembolic disease (deep vein thrombosis [DVT]/pulmonary embolism), peripheral vascular disease (claudication, rest pain, nonhealing ulcers), hematologic disorders (anemia, coagulopathies, blood dyscrasias), endocrine disorders (diabetes mellitus, thyroid disorders, steroid or glucocorticoid use), urologic disorders (benign prostatic hypertrophy, obstructive uropathy, prostate cancer, urinary tract infections), and infectious disease (human immunodeficiency virus [HIV], hepatitis, osteomyelitis). Patients should also be screened for malnutrition. Appropriate medical and surgical consults should be obtained preoperatively as needed.

●Obesity – While there is no weight limit for performing TKA, most surgeons would be concerned about performing a procedure in any patient with a body mass index (BMI) ≥40 kg/m² (severely obese). Patients who are overweight patients may be at a higher risk for perioperative and long-term complications; however, such patients are not denied surgical options, given their often debilitating osteoarthritis [12-15]. Furthermore, data suggest that TKA in patients with a BMI ≥40 kg/m² improved quality of life and is also cost-effective [16]. Weight loss prior to surgery may help to reduce the risk of infection and other perioperative complications (eg, anesthesia-related complications) and reduce the risk of surgical revision [17,18]. (See 'Reoperation' below.)

●Smoking – Smoking cessation is advised at least six weeks prior to surgery to at least six weeks postoperatively, although lifelong cessation is preferred. Smokers are at risk for developing surgical complications. In a review of 8776 patients who underwent TKA, 11.6 percent were current smokers. Compared with nonsmokers, smokers had increased rates of any wound complication (3.8 versus 1.8 percent), deep infection (2.5 versus 1.0 percent), pneumonia (1.3 versus 0.4 percent), and reoperation (5 versus 3.1 percent) [19-21]. (See "Risk factors for impaired wound healing and wound complications", section on 'Smoking and nicotine replacement therapy' and "Pharmacotherapy for smoking cessation in adults".)

Medications should be reviewed prior to surgery, with special attention to the degree of opioid use, which can impact outcomes, as well as antithrombotic therapies, such as aspirin and other antiplatelet therapies, anticoagulants (warfarin), and antiinflammatory agents (eg, NSAIDs, biologic agents) that may affect hemostasis during and after surgery or impair wound healing. Nutritional supplements such as vitamins and fish oil should be reviewed, some of which may have anticoagulation properties as well. (See "Perioperative medication management" and "Risk factors for impaired wound healing and wound complications" and "Preoperative evaluation and perioperative management of patients with rheumatic diseases".)

The overall success and durability of the TKA also depends upon several patient-related factors [22]. Prior to proceeding with TKA, it is important to consider patient age, the underlying disease leading to TKA, and the presence of comorbidities that may influence the perioperative management of the patient undergoing TKA. (See 'Reoperation' below.)

Knee imaging — Patients should have plain radiographs documenting advanced arthritic changes (ie, verifying bone-on-bone contact (image 1 and image 2)). If knee pain appears to be out of proportion to the radiographic appearance, other causes, such as spine and hip pathology and referred pain, should be excluded before arthroplasty is pursued. (See "Imaging techniques for evaluation of the painful joint".)

Plain radiographs are the mainstay imaging modality for preoperative planning and postoperative assessment following TKA. The three basic views that should be obtained in all patients include the following:

●Standing anteroposterior view – The anteroposterior view should be obtained with the patient standing in order to normally load the joint. The medial and lateral joint spaces should both be assessed for narrowing.

●Lateral view – The lateral view is used to assess the patellofemoral joint and the position of the patella (eg, patella baja, patella alta). It is also beneficial to obtain this image while the patient is standing.

●Tangential patellar view – The patellofemoral joint space should be assessed on a tangential patellar view ("sunrise," "skyline," or Merchant view).

Other views are sometimes used. As an example, a standing 45-degree posteroanterior radiograph may be ordered to more accurately determine joint space narrowing of the medial and lateral sides. A long-length standing film containing the hip, knee, and ankle joints is obtained to determine the anatomic and mechanical alignment of the limb (eg, varus, valgus), which is helpful for preoperative planning.

MRI and/or computed tomography (CT) scanning are generally not needed for patients being assessed for a routine TKA; however, these are sometimes used for preoperative planning, creation of patient-specific instrumentations, and templates for robotic surgery. In cases where standard radiographs do not demonstrate the expected advanced degenerative changes, MRI may be useful to detect other pathology (eg, osteonecrosis, large chondral lesions) if the indication for surgery is uncertain.

Laboratory studies — Preoperative laboratory requirements vary depending upon the patient's health and institutional policy, but they typically include a complete blood count, basic chemistry panel, and coagulation studies (prothrombin time, international normalized ratio [INR], and partial thromboplastin time). An electrocardiogram and a chest radiograph are usually required depending upon patient age and anesthesia policy. For patients with a history of infection, surveillance cultures (eg, blood, urine, tissue) following treatment must be negative (see "Preoperative medical evaluation of the healthy adult patient" and "Preoperative evaluation and perioperative management of patients with rheumatic diseases" and "Preoperative assessment of bleeding risk"). Issues related to performing a urinalysis in patients without urinary symptoms prior to TKA are discussed in detail separately. (See "Preoperative evaluation and perioperative management of patients with rheumatic diseases" and "Preoperative assessment of bleeding risk" and "Asymptomatic bacteriuria in adults", section on 'Joint arthroplasty'.)

Expected outcomes and informed consent — The patient must thoroughly understand the benefits and risks associated with TKA. While the primarily sought-after benefit of TKA is pain relief, improvement in function and quality of life is often reported to be higher compared with pain relief. In spite of a good surgical outcome, up to 25 percent of patients may remain dissatisfied [23-25]. Dissatisfaction following TKA surgery can be reduced as a result of extensive discussion and explanation before surgery [26].

●Pain relief – A systematic review documented that approximately 20 percent of recipients of total knee replacement report persistent or recurrent pain in the year or so following surgery [23,24]. Some of these patients are nonetheless satisfied, but it is important for patients to bear in mind that the risk of less than complete pain relief is not trivial. Research is ongoing to identify risk factors for a suboptimal outcome [25].

●Functional improvement – Patients generally experience dramatic improvements in the capacity to perform daily and community activities. Patients with worse functional status preoperatively tend to gain the most function following surgery, while patients with the best preoperative function tend to achieve the highest level of postoperative functional status [27]. While activities of daily living are generally easier to perform due to decreased knee pain following TKA, objective measures of knee function (eg, range of motion) typically improve less. The postoperative motion that can be expected is highly dependent on the preoperative motion [28].

●Correction of deformities – Patients with preoperative range of motion deficiencies should be counseled that the best predictor of their postoperative range of motion is their preoperative range of motion. Knee flexion contractures can be reduced in most cases by appropriate component selection and by soft tissue release [29]. Improvement in varus or valgus deformities is typically achieved.

The patient must also be aware of, and be fully able and willing to cooperate with, the rigors of the rehabilitation process following TKA. (See 'Contraindications' above and 'Rehabilitation' below.)

Timing of surgery for bilateral disease — The optimal period of time to stage bilateral procedures has not been well established [30,31]. Bilateral simultaneous knee arthroplasty has been associated with an increased risk for complications, and patients should be counseled as such. A meta-analysis demonstrated that simultaneous bilateral knee replacement increased the risk of serious cardiac and pulmonary complications, as well as mortality, compared with staged bilateral or unilateral surgery [30]. Similarly, a retrospective cohort study of a large health care database reported increased rates of pulmonary embolism, stroke, transfusion, and readmission at 90 days among patients with simultaneous bilateral knee replacements versus unilateral knee replacement [32]; it did not evaluate the risk compared with staged bilateral knee replacements.

Despite the possible risks of bilateral simultaneous knee arthroscopy, potential advantages include a shorter recovery and faster return to an improved quality of life. Patients who are of younger age with symmetrical end-stage knee osteoarthritis and who are willing to undergo bilateral simultaneous TKA should be counseled regarding the slightly increased mortality risk. Bilateral simultaneous TKA should only be performed in well-selected patients, using specialized anesthetic techniques, at an institution that is experienced in this type of surgery.

PERIOPERATIVE CARE

Antimicrobial prophylaxis — To reduce the risk for SSI, prophylactic antibiotics are given preoperatively. Infectious complications are uncommon but potentially serious. Wound dehiscence and surgical site infection (SSI) increase the risk for implant infection and may require additional surgical procedures to achieve eradication of infection and adequate coverage of the incision (picture 4). A more detailed discussion regarding antimicrobial prophylaxis in the setting of joint arthroplasty can be found elsewhere. Whether Staphylococcus aureus decolonization is beneficial for preventing infection is also discussed separately. (See "Prevention of prosthetic joint and other types of orthopedic hardware infection", section on 'Antimicrobial prophylaxis' and "Overview of control measures for prevention of surgical site infection in adults", section on 'S. aureus decolonization'.)

Thromboprophylaxis — Patients undergoing total knee arthroplasty (TKA) are considered to be at high risk for venous thromboembolism (VTE; deep vein thrombosis [DVT], pulmonary embolism [PE]). VTE is a potentially lethal complication of knee surgery. The reported incidence of DVT following TKA without prophylaxis ranges from 40 to 88 percent [33]. The incidences of asymptomatic PE, symptomatic PE, and mortality are 10 to 20 percent, 0.5 to 3 percent, and up to 2 percent, respectively. By contrast, the incidence of symptomatic VTE is reduced significantly to approximately 1 percent with prophylactic anticoagulation; however, VTE is not prevented altogether.

We recommend postoperative thromboprophylaxis in patients undergoing TKA; the method used is chosen based upon balancing the risk of VTE and the risk of bleeding associated with a particular strategy. There is considerable variability in practice among orthopedic surgeons. Our practice is generally consistent with guidelines from the American College of Chest Physicians (ACCP), the American Society of Hematology (ASH), and the American Academy of Orthopaedic Surgeons (AAOS). The approach to prevent thromboembolic disease in patients undergoing TKA is discussed in detail separately. (See "Prevention of venous thromboembolism in adults undergoing hip fracture repair or hip or knee replacement".)

Anesthetic considerations — TKA can be performed with general anesthesia (GA) or neuraxial anesthesia (ie, spinal, epidural, or combined spinal epidural [CSE]). The choice of anesthetic technique should be based on patient comorbidities and patient choice and is discussed in detail separately. (See "Anesthesia for total knee arthroplasty", section on 'General versus regional anesthesia'.)

Perioperative pain control — The goal for pain management after TKA is to provide effective analgesia that allows immediate rehabilitation and early mobilization. Multimodal strategies for postoperative pain control after TKA have reduced the need for intravenous opioids and may include acetaminophen, nonsteroidal antiinflammatory drugs (NSAIDs), gabapentinoids, regional anesthesia techniques, and periarticular local anesthetic infiltration. (See "Anesthesia for total knee arthroplasty", section on 'Plan for perioperative multimodal pain control'.)

●Peripheral nerve block – Single-injection and continuous peripheral nerve blocks are widely used for postoperative analgesia after TKA. Multiple studies have reported reduced perioperative complications and enhanced patient satisfaction with the use of peripheral nerve blocks compared with traditional opioid therapy [34-37].

Sensory innervation of the knee includes the femoral, sciatic, and obturator nerves. These nerves can be individually blocked, but, more commonly, a single block of the femoral nerve or its distal sensory branches (ie, the saphenous nerve and nerve to vastus medialis at the adductor canal) is performed to provide partial, usually adequate, analgesia (since the vast majority of the innervation of the knee is from the femoral nerve). The adductor canal block is increasingly used because it is associated with less quadriceps weakness [38-40], which may therefore facilitate early mobilization and rehabilitation and may reduce the risk of patient falls while the block is in effect. (See "Anesthesia for total knee arthroplasty", section on 'Peripheral nerve blocks'.)

●Periarticular infiltration – Periarticular wound infiltration by the surgeon is an emerging technique for postoperative pain control after TKA. This technique has not been standardized; solutions including long-acting local anesthetics and adjuvants (eg, NSAIDs, opioids) or liposomal local anesthetic solutions are often used [37,41-48]. (See "Anesthesia for total knee arthroplasty", section on 'Periarticular injection (PAI)/local infiltration analgesia (LIA)'.)

●Lumbar epidural analgesia – Postoperative continuous epidural analgesia is often used if epidural or combined spinal and epidural anesthesia is used for surgery. (See "Continuous epidural analgesia for postoperative pain: Technique and management".)

TOTAL KNEE ARTHROPLASTY PROCEDURE — Total knee arthroplasty (TKA) consists of resecting the diseased articular surfaces of the knee, followed by resurfacing with metal and polyethylene prosthetic components (image 3) [5]. Patients are positioned supine on the operating table.

Total knee arthroplasty implant design — The introduction of the "total condylar prosthesis" by Insall and colleagues in 1972 is generally considered to mark the era of "modern" knee replacement. This prosthesis was the first to replace all three compartments of the knee. There are many variations of the original design, with the modern-day prosthesis representing a modular evolution of Insall's original design [49].

All TKAs consist of a femoral component, a tibial component, and a patellar component. There are a large number of manufacturers and designs of knee prostheses. Most available systems are modular with a metal tibia tray with polyethylene spacers that articulate with the femoral component. Designs can either retain the posterior cruciate ligament (PCL; eg, PCL retention/cruciate retaining [CR]) or remove the PCL (eg, PCL sacrificing/posterior stabilized [PS], cruciate substituting [CS]). Most currently used designs involve resection of the anterior cruciate ligament (ACL). More constrained designs are also available (eg, hinged implants) for situations including severe deformity, instability, and revision surgery. In general, a more constrained implant shifts more force onto the components, potentially leading to higher failure rates.

Fixation techniques involve either using cement to fix the prosthesis to the bone or relying on bone growth into and onto the prosthesis surface (cementless). This is often assisted by the use of hydroxyapatite and other surface changes on the prosthesis to enhance fixation.

Implant selection is surgeon-dependent. There is no consensus on implant choice, and there is wide variation among nations, states, cities, and individual surgeons. The variability of implant design and technique makes it difficult to analyze and generalize reported results. National joint replacement registries are enabling the analysis of the survival rates of joint replacements to be calculated based on revision surgery, if it is performed. The Australian National Joint Replacement Registry publishes its results every year in great detail, and the 2021 report was based on the results of 911,953 knee replacement procedures [50]. The American Joint Replacement Registry was created in 2009 and is rapidly becoming the world's largest joint replacement registry.

Minimizing perioperative blood loss — Perioperative blood loss for TKA can be minimized by using blood-saving techniques (tourniquet, topical agents, systemic agents). Other general measures to reduce blood loss are discussed separately. (See "Perioperative blood management: Strategies to minimize transfusions".)

Tourniquet use — To control bleeding from the cancellous bone and intramedullary cavity during drilling, a pneumatic cuff (tourniquet) is commonly (although not always) placed on the thigh during the initial setup. It is not typically inflated until after prepping and draping the patient to reduce the amount of inflation time, and it is typically deflated just prior to closing the wound. The total tourniquet time for the majority of knee specialist surgeons is approximately 60 to 90 minutes. The benefit of tourniquet use is a clean operative field not complicated by blood, less intraoperative blood loss, reduced operative time, and possibly better fixation of cement given a drier bony surface [51]. However, the use of a tourniquet may increase the risk for postoperative venous thrombosis, increased pain thereby increasing medication requirements, and reduced early range of motion and potentially a delay in early rehabilitation. Whether blood loss is reportedly reduced depends on how blood loss is measured and possibly on the timing of tourniquet release [52].

In a meta-analysis of 13 randomized trials, reported intraoperative blood loss was less in the group using a tourniquet; however, in studies where visible blood loss or calculated blood loss was reported, the results were similar between the groups, and transfusion requirements were also similar [53]. Nevertheless, the overall rate of complications was higher when a tourniquet was used, and it was concluded that TKA without a tourniquet led to overall better outcomes. A later systematic review and meta-analysis also reported an increased risk of serious adverse events with the use of a tourniquet (21 studies: 53 versus 26 per 1000; relative risk 1.73, 95% CI 1.10-2.73) [54,55].

Tranexamic acid — Tranexamic acid, an antifibrinolytic agent, is typically used during TKA to minimize blood loss. We give 1 g of tranexamic acid intravenously before incision and 1 g of tranexamic acid intravenously during closure, but regimens may vary, and the optimal approach is not known. If needed, tranexamic acid can also be given in the postoperative period. Additional information regarding the efficacy, dosing, and risks of tranexamic acid use during TKA is presented separately. (See "Anesthesia for total knee arthroplasty", section on 'Antifibrinolytics'.)

Topical, systemic (oral, intravenous), and combinations of administration routes of tranexamic acid have all been used in conjunction with knee arthroplasty [56-62]. Prophylactic systemic tranexamic acid administration may be more effective than topical application, but this finding has not been universal [63,64]. Regardless of route of administration, in randomized trials [65-77], tranexamic acid has reduced the need for perioperative transfusion compared with controls (ie, no drug; with or without tourniquet).

One trial has suggested that continuing tranexamic acid into the postoperative period may have added benefits. In the TRAC-24 trial [66], 552 patients were randomly assigned to no tranexamic acid, intraoperative tranexamic acid (1 g intravenous) at the time of surgery, or tranexamic acid at the time of surgery with additional oral tranexamic acid postoperatively for 24 hours. When comparing the two intervention groups, the mean indirect blood loss (IBL) was less for those who received additional postoperative dosing compared with intraoperative only dosing (mean difference -125.8 mL, 95% CI -194.0 to -57.5). Mortality and thromboembolic events were similar across the groups.

Arthroplasty technique — The knee is typically approached via a midline skin incision (figure 2). When previous knee scars are present, all attempts are made to incorporate the prior skin incisions. With multiple knee scars, the most lateral is usually used to optimize the blood supply to the skin flap. On occasion, preoperative plastic surgery consult is needed to aid with planning in knees with multiple scars.

The majority of surgeons use a medial parapatellar approach to enter the knee for initial TKA. With this approach, an incision is made in the quadriceps tendon above, down along the medial side of the patella, down to the medial aspect of the tibial tubercle. The medial parapatellar approach allows for lateral eversion or subluxation of the patella. Occasionally, the lateral parapatellar approach is used for a valgus knee. Other approaches include subvastus and midvastus approaches.

Once the knee joint is entered, the soft tissue is removed from the joint (menisci and ACL, possibly PCL, depending on prosthesis type), and osteophytes are removed from the edges of the bone.

Several technologies have been developed to enable the surgeon to implant the TKA implant more accurately. Manual instruments referencing the bony alignment and surfaces, computer navigation systems, and patient-specific guides are used to assist surgeons in making the required bony cuts to facilitate the placement of the prosthetic components. Individualized cutting guides are based directly on the patient's anatomy using a preoperative MRI or CT scan (see 'Knee imaging' above) [78-80]. Robotic systems are also being used to assist with bone preparation and the placement of implants in TKA. Trial implants are also used to assess for balance prior to putting in the final implant. The use of intramedullary (IM) rods to reference alignment should be avoided (unilateral or bilateral TKA) because it has been associated with increased postoperative mortality compared with techniques that do not use IM rods [81,82].

The patella may or may not be resurfaced. Patella resurfacing, typically with a polyethylene button, remains a controversial topic in TKA [83]. There is some evidence that resurfacing the patella might lessen anterior knee pain postoperatively and therefore reduce the need for a second operation to resurface the patella. However, the advantage of not resurfacing, which includes preserving bone stock and reducing patellofemoral complications such as fractures and loosening, may offset the potential reduction in pain. (See "Complications of total knee arthroplasty", section on 'Patellofemoral disorders'.)

Ligamentous releases may be required for adequate soft tissue balance, particularly if the knee had a significant preoperative deformity. Varus knees are usually tight medially and lax laterally. Valgus knees are usually tight laterally and lax medially. Soft tissue balance is typically achieved by performing releases on the capsuloligamentous structures on the tight side. The PCL may be retained or sacrificed. (See 'Handling the posterior cruciate ligament' below.)

The bony surfaces can be cleaned of blood and fat via pulse lavage and dried with fresh sponge. The femoral and tibial components are prepared with balance in flexion/extension, varus/valgus, and rotation; cementless or cemented implants may be used. At this stage, the cement is mixed if it is to be used. The cement is applied to the tibia, femur, and the prosthesis and impacted to the bone with the excess removed carefully. Cement is also applied to the patella, and the patella button is applied. After approximately 10 minutes, the cement will have hardened, and the joint is irrigated again with pulse lavage to remove any debris.

The wound is closed in layers starting with the retinaculum, then fat, subcutaneous tissue, and finally skin. The tourniquet is deflated prior to closure to assess for any bleeding and achieve hemostasis [84].

Handling the posterior cruciate ligament — Whether to retain or sacrifice the PCL is controversial. PCL sacrificing is also called substitution because the tibial polyethylene component requires the addition of a post to provide the stability normally provided by the PCL. Both PCL retention and PCL sacrificing designs have compelling theoretical reasons for their existence.

●Theoretical advantages of PCL retention include greater range of motion due to reproduction of femoral rollback, decreased stress on the implant leading to lower rates of failure, improved proprioception in stair climbing, and preservation of bone stock [33].

●Theoretical advantages of PCL sacrificing include more reliable correction of deformity; easier balancing of the knee; and elimination of excessive femoral rollback, which may compromise implant fixation and which may increase conformity of the prosthesis, thus leading to decreased contact stresses and to decreased polyethylene wear [33].

However, most of the purported advantages for either approach have not been realized in clinical studies, and excellent results may be obtained with either design [83,85-91]. A systematic review of 17 randomized trials with 1810 patients assessed the benefits and harms of retention compared with sacrifice of the PCL in TKA in osteoarthritis patients. It found no clinically relevant differences with respect to range of motion, pain, and clinical and radiologic outcomes [92].

POSTOPERATIVE COURSE AND FOLLOW-UP — Postoperative management includes pain management, prophylaxis against venous thromboembolism (VTE), minimization of postoperative morbidity, and appropriate physical therapy (PT) to achieve the best possible knee motion and return to full function as safely as possible.

Patients are generally mobilized the day of surgery and, with the aid of the physiotherapist, can usually walk with assistive devices on postoperative day 1. The length of hospitalization varies from zero to five days, depending on comorbidities and local practice. Total knee arthroplasty (TKA) is trending toward being performed on an outpatient basis in selected low-risk patients and with discharge to home directly rather than to a rehabilitation unit. TKA is increasingly being performed in ambulatory surgery centers [93,94]. (See "Anesthesia for total knee arthroplasty", section on 'Outpatient total knee arthroplasty (same day discharge)'.)

The first signs of clinical improvement compared with preoperative status generally occur between 6 and 12 weeks postoperatively with full recovery occurring between one and two years postoperatively.

Postoperative care potentially includes pain management utilizing the acute pain services, postoperative knee radiography, complete blood test (particularly hemoglobin) and electrolytes on day one; and ongoing thromboprophylaxis and antimicrobial prophylaxis.

Rehabilitation — There is no clear consensus regarding the optimal frequency, duration, or intensity of physical rehabilitation protocols for TKA patients [95]. However, participation by the patient in a postoperative rehabilitation program is required for a successful outcome following TKA. A well-structured PT program that includes range of motion exercises, gait training, quadriceps strengthening, and training in activities of daily living is an important component of the rehabilitation process. Rehabilitation goals should be realistic.

Interventions that attempt to preserve knee motion include the use of pillows under the operative foot while in bed to maintain extension and to avoid flexion contracture. Active and passive exercises to achieve maximal flexion should be instituted early with appropriate use of analgesia to minimize pain. Realistic expectations on flexion range should be based on preoperative flexion and average flexion of total knee replacements around the world being around 115 degrees [96].

Range of motion exercises should be started as soon as possible. A 2007 meta-analysis of five randomized trials concluded that participation after discharge from the hospital in a functional exercise program supervised by a physical therapist improves knee function and range of motion in the short term when compared with routine care [97]. Inpatient rehabilitation has not been shown to result in improved mobility compared with home-based PT in patients who have undergone an uncomplicated TKA [98].

Follow-up and activity level — Following the surgery, depending on the indication for the surgery and the conduct of the operation, the patient may follow up with their provider.

The typical follow-up schedule starts with wound review within two weeks of surgery. This can be done by an internist, nurse practitioner, rehabilitation doctor, physiotherapist, or the surgeon. The patient typically sees the surgeon at six to eight weeks with or without a repeat knee radiograph. Subsequent follow-up is highly variable.

In the long term, patients are encouraged to pursue low- to moderate-intensity, low-impact exercises. Walking, swimming, and moderate activity are always encouraged for maintaining strength and physical and mental well-being. This level of activity should be expected following TKA. The role of a total knee replacement is to alleviate pain so that patients can return to their daily activities. More vigorous activities, including sports, are possible following TKA but are often not recommended, despite uncertainty regarding any risks to the knee as a result of these activities [99,100].

OUTCOMES

Morbidity and mortality — Mortality following total knee arthroplasty (TKA) is overall low, ranging from 0.5 to 1 percent per year, and is primarily related to preexisting medical comorbidities [6,101-103]. Surgeon volume impacts surgical outcomes as there is evidence that low-volume surgeons and hospitals are associated with worse outcomes compared with high-volume surgeons and hospitals [104,105].

Complications — Complications associated with TKA include those in common with other surgeries, such as those related to anesthesia or blood transfusion, venous thromboembolism (VTE), and surgical site infection (SSI), as well as complications specific to operations involving the knee joint, including neurovascular injury, prosthetic joint infection, peri-implant fractures, patellofemoral disorders, and issues related to wear and tear of the prosthetic. These specific complications are discussed separately. (See "Complications of total knee arthroplasty".)

Reoperation — Reoperation may be needed for a variety of problems related to TKA (eg, implant wear, aseptic loosening, implant infection, patellofemoral disorders, peri-implant fracture). (See "Complications of total knee arthroplasty".)

Loosening of the prosthesis and infection are the main reasons for revision [50,106]. Males have a higher revision rate, mostly secondary to higher rates of infection. For patients with primary osteoarthritis, the revision rate in Australia is 4.8 percent in 10 years and 8.1 percent at 20 years. Revision rates in patients with rheumatoid arthritis is slightly lower, and for patients with osteonecrosis or other inflammatory arthritis, the revision rate is slightly higher [50].

A large meta-analysis including data from national registries estimated that approximately 82 percent of total knee replacements last 25 years [107]. The longevity of the implant largely reflects the total load that the implant bears over time. In general, younger TKA recipients use their implants at a more active time in their lives. Thus, the devices are much more likely to fail in their lifetime compared with the implant in older TKA recipients. The impact of patient age on the likelihood of needing revision surgery was evaluated in a large population-based study including 54,276 patients aged 50 or older who had undergone a TKA between 1991 and 2011 [108]. The lifetime risk of revision surgery in patients who had a TKA over the age of 70 years was approximately 5 percent, with no difference between males and females. However, the lifetime risk of revision increased with decreasing age, with the highest risk of 35 percent observed in males between the ages of 50 and 54. The risk of surgical revision appears to be even higher in patients under the age of 50, suggesting that TKA should be undertaken cautiously in these patients. In another population-based study that included 120,538 patients who had undergone TKAs, almost 5 percent of patients under 50 years old required revision surgery at one year [109].

As with age, underlying disease also plays a role in the longevity of the prosthesis. Rheumatoid arthritis patients are generally less active, placing less of a load on the joint compared with osteoarthritis patients. A survivorship analysis of 11,606 TKAs found that the durability of the prosthesis was shorter in patients with osteoarthritis compared with those with inflammatory arthritis (10-year prosthesis survival of 90 versus 95 percent, respectively) [22].

Obesity also has a negative effect on outcome after TKA [12,110]. In a 2012 meta-analysis, patients who were obese (body mass index [BMI] ≥30 kg/m²) had increased rates of infection (odds ratio [OR] 1.90, 95% CI 1.47-2.47) and revision for any reason (OR 1.30, 95% CI 1.02-1.67) compared with patients who were not obese [110].

Implant infection may result in prolonged hospitalization, the need to remove the infected implant, and an extended course of antibiotic treatment, followed by reimplantation. Up to 1 percent of total knee replacement recipients experience an infected prosthesis over the course of the first postoperative year. Prolonged infection treatment may lead to multiple surgeries, fusion, or even amputation. (See "Prosthetic joint infection: Epidemiology, microbiology, clinical manifestations, and diagnosis" and "Prevention of prosthetic joint and other types of orthopedic hardware infection" and "Prosthetic joint infection: Treatment".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Total knee arthroplasty".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Deciding to have a knee replacement (The Basics)")

●Beyond the Basics topics (see "Patient education: Total knee replacement (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Total knee arthroplasty – Total knee arthroplasty (TKA), also known as total knee replacement, consists of resection of the diseased articular surfaces of the knee, followed by resurfacing with metal and polyethylene prosthetic components. For the properly selected patient, the procedure results in significant pain relief, as well as improved function and quality of life. In spite of the potential benefits of TKA, it is an elective procedure and should only be considered after thorough discussion of the risks, benefits, and alternatives. (See 'Introduction' above.)

●Candidates – The most common indication for TKA is for the relief of pain associated with osteoarthritis of the knee in patients who have failed nonoperative treatments. Other conditions that cause pain resulting in the need for TKA include inflammatory arthritides (eg, rheumatoid arthritis, psoriatic arthritis, spondyloarthritis), crystal-induced arthritis (eg, gout), posttraumatic arthritis, sequelae of infection, tumor, avascular necrosis (osteonecrosis), or congenital joint abnormalities. Loss of function and deformity are less common but clinically important indications as well. (See 'Indications' above.)

●Contraindications – Contraindications to TKA include active infection in the knee or anywhere in the body, a nonfunctioning extensor mechanism, chronic lower extremity ischemia not amenable to revascularization, and skeletal immaturity. Patient participation in a postoperative rehabilitation program is essential for a successful outcome following TKA, and an inability to participate may constitute a relative contraindication to this form of treatment. (See 'Contraindications' above.)

●Preoperative evaluation – A careful preoperative evaluation must be performed to verify the severity of the underlying knee pathology and the failure of conservative treatments, as well as identify any medical comorbidities that might impact the choice of anesthesia, the conduct of the operation, and possible complications. A thorough evaluation includes particular elements of the history, a physical examination, imaging and laboratory studies, a review of treatment alternatives, and discussions of the benefits and risks of the procedure. (See 'Preoperative evaluation' above.)

●Antibiotic prophylaxis – Antibiotics (table 1) are given preoperatively to reduce the risk for surgical site infection (SSI) and prosthetic joint infection. Postoperative thromboprophylaxis should also be administered in patients undergoing TKA. The approach to thromboprophylaxis in adult orthopedic surgery as well as the use of antimicrobial prophylaxis are discussed in detail separately. (See "Prevention of venous thromboembolism in adults undergoing hip fracture repair or hip or knee replacement" and "Prevention of prosthetic joint and other types of orthopedic hardware infection".)

●Anesthesia – TKA can be performed with general or neuraxial (ie, spinal, epidural, or combined spinal epidural [CSE]) anesthesia. Regional anesthesia techniques and/or periarticular local anesthetic infiltration are increasingly used as part of multimodal opioid-sparing strategies for postoperative pain management. (See 'Anesthetic considerations' above and 'Perioperative pain control' above and "Anesthesia for total knee arthroplasty".)

●Procedure – All TKAs consist of a femoral component, a tibial component, and a patellar component (figure 2). There are a large number of manufacturers and designs of knee prostheses. Most available systems are modular with a metal tibia tray with polyethylene spacers. Designs can either retain or remove the posterior cruciate ligament (PCL). (See 'Total knee arthroplasty procedure' above.)

●Postoperative care – Postoperative care can include pain management, prophylaxis against infection, venous thromboembolism (VTE) prophylaxis, and minimization of postoperative morbidity, as well as appropriate physical therapy (PT) to achieve the best possible knee motion and return to full function as quickly and safely as possible. The first signs of clinical improvement compared with preoperative status generally occur between 6 and 12 weeks postoperatively with full recovery occurring between one and two years postoperatively. (See 'Postoperative course and follow-up' above.)

●Morbidity and mortality – Mortality following TKA is overall low, ranging from 0.5 to 1 percent per year, and is primarily related to preexisting medical comorbidities. Complications associated with TKA include those in common with other surgeries (eg, SSI), as well as those specific to operations involving the knee joint (eg, prosthetic joint infection). Reoperation may be needed for a variety of problems related to TKA (eg, implant wear, aseptic loosening, implant infection, patellofemoral disorders, peri-implant fracture) that may lead to implant/joint failure or patient dissatisfaction. Loosening of the prosthesis and infection are the main reasons for revision. Complications specific to knee arthroplasty are discussed in detail separately. (See 'Morbidity and mortality' above and "Complications of total knee arthroplasty".)

ACKNOWLEDGMENTS — The UpToDate editorial staff acknowledges Thomas Thornhill, MD, Jeffrey Katz, MD, MSc, and Justin Roe, MBBS, BSc (Med) Hons, FRACS, who contributed to an earlier version of this topic review.