Total Knee Arthroplasty (TKA)

Total knee replacement (TKR) in some form has been practiced for more than 50 years, but in the earliest days of the procedure, the complexities of the knee joint were not fully understood. Because of this, TKR initially was not as successful as Sir John Charnley's artificial hip. However, dramatic advances in the knowledge of knee mechanics have led to design modifications that appear to be durable.

Significant advances have occurred in the type and quality of the metals, polyethylene, and ceramics used in the prosthesis manufacturing process, leading to improved longevity. As with most techniques in modern medicine, more and more patients are receiving the benefits of total knee arthroplasty (TKA).[3, 4]  In 2020, according to the 2021 annual report from the American Joint Replacement Registry (AJRR), 124,307 primary TKAs were performed in the United States, along with 10,526 revision knee arthroplasties and 5857 partial knee arthroplasties.[5]

In the 1860s, Fergusson reported performing a resection arthroplasty of the knee for arthritis. Verneuil is thought to have performed the first interposition arthroplasty using joint capsule. Other tissues were subsequently tried, including skin, muscle, fascia, fat, and even pig bladder.

The first artificial implants were tried in the 1940s as molds fitted to the femoral condyles following similar designs in the hip. In the next decade, tibial replacement was also attempted, but both designs had problems with loosening and persistent pain.

Combined femoral and tibial articular surface replacements appeared in the 1950s as simple hinges. These implants failed to account for the complexities of knee motion and consequently had high failure rates from aseptic loosening. They were also associated with unacceptably high rates of postoperative infection.

In 1971, Gunston importantly recognized that the knee does not rotate on a single axis like a hinge; rather, the femoral condyles roll and glide on the tibia with multiple instant centers of rotation. His polycentric knee replacement had early success with its improved kinematics over hinged implants but was ultimately unsuccessful because of inadequate fixation of the prosthesis to bone.

The highly conforming and constrained Geomedic knee arthroplasty introduced in 1973 at the Mayo Clinic ignored Gunston's work, and a kinematic conflict arose. Other designs followed, either following Gunston's principle in attempting to reproduce normal knee kinematics or allowing a conforming articulation to govern knee motion.

The total condylar prosthesis was designed by Insall at the Hospital for Special Surgery in 1973. This prosthesis concentrated on mechanics and did not try to reproduce normal knee motion. In 1993, Ranawat et al reported a rate of survivorship of 94% at 15 years of follow-up, which is the most impressive reported to date.[6]

The component was subsequently altered to artificially introduce normal kinematics so as to improve the component's range of motion (ROM). At the same time, a prosthesis with more natural kinematics was developed at the Hospital for Special Surgery, relying on the retained cruciate ligaments to provide knee motion.

The argument over whether knee ligaments should be preserved or sacrificed continues to this day. Long-term follow-up studies do not show any significant differences, though gait appears to be less abnormal if ligaments are preserved, especially when walking up and down stairs. One theoretical way of incorporating normal kinematics and maximal conformity is to use mobile tibial bearings. Midterm follow-up studies of these prostheses have shown encouraging results.

Cemented TKR procedures have been the criterion standard for TKA, but uncemented designs with bioactive surfaces (eg, hydroxyapatite) have shown promising midterm results (see the image below).[7, 8]

For patient education information, see the Foot, Ankle, Knee, and Hip Center, Bone Health Center, and Arthritis Center, as well as Knee Joint Replacement and Knee Pain.

The primary indication for TKA is to relieve pain caused by severe arthritis. The pain should be significant and disabling. Night pain is particularly distressing. If dysfunction of the knee is causing significant reduction in the patient's quality of life, this should be taken into account.

Correction of significant deformity is an important indication but is rarely used as the primary indication for surgery. Roentgenographic findings must correlate with a clear clinical impression of knee arthritis. Patients who do not have significant loss of joint space tend to be less satisfied with their clinical result after TKA. All conservative treatment measures should be exhausted before surgery is considered.

Knee replacement has a finite expected survival that is adversely affected by activity level.[6, 9, 10] Generally, it is indicated in older patients with more modest activities. It is also clearly indicated in younger patients who have limited function because of systemic arthritis with multiple joint involvement. Young patients requesting knee replacement, especially those with posttraumatic arthritis, are not excluded by age but must be significantly disabled and must understand the inherent limitations on the longevity of joint replacement.

Rarely, severe patellofemoral arthritis (see the image below) may justify arthroplasty on the grounds that the expected outcome of arthroplasty is superior to that of patellectomy. Isolated patellofemoral replacement still is undergoing clinical investigation.

Deformity can sometimes become the principal indication for knee replacement in patients with moderate arthritis when flexion contracture or varus or valgus laxity is significant. In such cases, a more constrained prosthesis is often required, leading to greater technical difficulty in surgery and greater uncertainty regarding long-term survival.

Absolute contraindications for TKA include the following:

• Knee sepsis
• A remote source of ongoing infection
• Extensor mechanism dysfunction
• Severe vascular disease
• Recurvatum deformity secondary to muscular weakness
• Presence of a well-functioning knee arthrodesis

Relative contraindications include medical conditions that preclude safe anesthesia and the demands of surgery and rehabilitation. Other relative contraindications include the following:

• Skin conditions within the field of surgery (eg, psoriasis)
• Past history of osteomyelitis around the knee
• Neuropathic joint
• Obesity

Anatomy

Movement of the knee joint can be classified as having six degrees of freedom, comprising three translations and three rotations, as follows:

• Translations - (1) Anterior/posterior, (2) medial/lateral, and (3) inferior/superior
• Rotations - (1) Flexion/extension, (2) internal/external, and (3) abduction/adduction

Movements of the knee joint are determined by the shape of the articulating surfaces of the tibia and femur and the orientation of the four major ligaments of the knee joint. The anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL; see the image below), the medial collateral ligament (MCL), and the lateral collateral ligament (LCL) serve as a four-bar linkage system.

Knee flexion/extension involves a combination of rolling and sliding called femoral rollback, which is an ingenious way of allowing increased ranges of flexion. Because of asymmetry between the lateral and medial femoral condyles, the lateral condyle rolls a greater distance than the medial condyle during 20º of knee flexion. This causes coupled external rotation of the tibia, which has been described as the screw-home mechanism of the knee that locks the knee into extension.

Medial and lateral collateral ligaments

The primary function of the MCL is to restrain valgus rotation of the knee joint, with its secondary function being control of external rotation. The LCL restrains varus rotation and resists internal rotation.

Anterior cruciate ligament

The primary function of the ACL is to resist anterior displacement of the tibia on the femur when the knee is flexed and control the screw-home mechanism of the tibia in terminal extension of the knee. A secondary function of the ACL is to resist varus or valgus rotation of the tibia, especially in the absence of the collateral ligaments. The ACL also resists internal rotation of the tibia.

Posterior cruciate ligament

The main function of the PCL is to allow femoral rollback in flexion and resist posterior translation of the tibia relative to the femur. The PCL also controls external rotation of the tibia with increasing knee flexion. Retention of the PCL in TKR has been shown biomechanically to provide normal kinematic rollback of the femur on the tibia. This also is important for improving the lever arm of the quadriceps mechanism with flexion of the knee.

Patellofemoral joint

Movement of the patellofemoral joint can be characterized as gliding and sliding. During flexion of the knee, the patella moves distally on the femur. This movement is governed by the attachments of the patellofemoral joint to the quadriceps tendon, the ligamentum patellae, and the anterior aspects of the femoral condyles. The muscles and ligaments of the patellofemoral joint are responsible for producing extension of the knee.

The patella acts as a pulley in transmitting the force developed by the quadriceps muscles to the femur and the patellar ligament. It also increases the mechanical advantage of the quadriceps muscle relative to the instant center of rotation of the knee.

Mechanical axis

The mechanical axis of the lower limb is an imaginary line through which the weight of the body passes. It runs from the center of the hip to the center of the ankle through the middle of the knee. This axis is altered in the presence of deformity and must be reconstituted at surgery, which allows normalization of gait and protects the prosthesis from eccentric loading and early failure.

See Knee Joint Anatomy for more information.

Procedural planning

A number of operative procedures should be considered in patients with degenerative disease of the knee. Arthroscopic debridement is sometimes indicated in mild degenerative joint disease with mechanical symptoms and recurrent persistent effusions. Proximal tibial valgus osteotomy should be reserved for patients with medial tibiofemoral compartment disease, stable collateral ligaments, and a correctable varus deformity of the knee joint (see the image below).

Similarly, a distal femoral varus osteotomy can be considered for patients with lateral tibiofemoral compartment disease, stable collateral ligaments, and a valgus deformity of the knee joint (see the image below).

These procedures restore the mechanical axis of the lower limb and offload the diseased compartment. Proximal tibial valgus osteotomy and distal femoral varus osteotomy are generally reserved for young high-demand patients because of concerns about the durability of TKA in this patient group.

A prospective, randomized, controlled trial in England compared unicompartmental knee replacement with TKA over 8, 10, 12, and 15 years of follow-up. At 5 years, the number of failures were equal in the two groups. At 15-year follow-up, the survivorship rate was 89.8% for unicompartmental knee replacement and 78.7% for TKA. Four of the unicompartmental knees failed, and six of the TKA knees failed. Newman et al determined from their findings that the results of their study justify increased use of unicompartmental replacement.[11]

Arthrodesis or fusion of the knee is rarely performed but should be considered in patients with chronic sepsis, younger patients with tricompartmental disease (eg, following trauma) who require stability and durability, and patients with deficient extensor mechanisms. TKA is performed in patients with symptomatic advanced degenerative changes in one or more compartments of the knee joint.

A randomized controlled trial by Batailler et al (N = 118) assessed survival rates, clinical outcomes, and radiologic results of TKA with either cemented tibial and femoral components (n = 59) or a hybrid approach with uncemented femoral components and cemented tibial components (n = 59).[12]  Patients were between the ages of 50 and 90 years, underwent primary TKA for osteoarthritis without a history of open knee surgery, and were followed for a minimum of 10 years. No significant differences were found between cemented TKA and hybrid TKA with respect to survivorship, complication rate, clinical scores, or radiologic signs of loosening.

A study of 118 elderly (>65 y) female patients undergoing TKA by Kwon et al found that underweight patients had poorer clinical outcomes than those with a normal body mass index (BMI), though the two groups did not differ significantly with regard to postoperative complications.[13]

A thorough preoperative medical evaluation of patients undergoing total knee arthroplasty (TKA) is important for preventing potential complications in the perioperative period. The evaluation should be completed in an elective preadmission clinic well before the date for surgery. This allows for a careful and unhurried assessment with adequate time for investigations, specialist anesthetic and medical opinion, and consent. It also allows operating schedules to be reorganized if patients are deferred from surgery.

Most patients who undergo TKA are elderly and have various comorbid conditions. Patients must have good cardiopulmonary function to withstand anesthesia and to withstand a blood loss of 1000-1500 mL over the perioperative period. Routine preoperative electrocardiography (ECG) should be performed on elderly patients. Patients with ischemic heart disease, congestive heart failure, and chronic obstructive airway disease should be seen by a medical specialist or anesthetist. Patients with significant peripheral vascular disease should be seen by a vascular surgeon.

Patients should have completed an informed consent for surgery and fully understand the risks and possible complications of the procedure. They should have had all medical conditions optimized before surgery and should be free of intercurrent infections. Two units of blood should be available for perioperative transfusion, either from the blood bank or, preferably, as predonated blood. Full medical and surgical backup must be available in case unforeseen complications occur.

Laboratory studies

Preoperative laboratory evaluation should include the following:

• Complete blood count (CBC)
• Erythrocyte sedimentation rate (ESR)
• Serum electrolytes
• Renal function studies
• Prothrombin time (PT) and activated partial thromboplastin time (aPTT)
• Urinalysis and urine culture

Urinalysis is performed to exclude occult urinary tract infection (UTI). Routine preoperative coagulation studies are not necessary except in patients with a history of bleeding, alcoholism, or previous liver disease.

Imaging studies

Radiographic views for the assessment of the patient with knee arthritis include the following:

• Standing anteroposterior (AP) view
• Lateral view
• Patellofemoral (skyline) view (see the image below)
• Long leg radiographs to assess malalignment - Helpful for preoperative planning
• Standing radiographs with the knee in extension or in 45º of flexion (Rosenberg view) - Can improve the sensitivity of detection of cartilage degeneration

Loss of joint space, cysts, subchondral sclerosis, and osteophytes confirm the diagnosis of osteoarthritis (see the image below).

Routine chest roentgenography is not usually recommended as a screening tool. However, it is indicated in patients with cardiopulmonary disease or in patients with clinical signs identified in the preadmission clinic.

Other preoperative tests

ECG is performed in elderly patients and in patients with a history of cardiac issues.

More sophisticated imaging modalities in the investigation of knee arthritis are of occasional benefit for the assessment of significant bone loss or bone infection and include the following:

• Indium white blood cell (WBC) scanning
• Computed tomography (CT)
• Magnetic resonance imaging (MRI)
• Bone densitometry

Different types of TKA prostheses are available (see the image below). These include the following:

• Fixed bearing
• Medial pivot
• Rotating platform and mobile bearing
• Posterior cruciate ligament (PCL)-retaining
• PCL-substituting

Anesthesia

TKA may be performed with the patient under regional or general anesthesia. Selection of regional or general anesthesia is made following preoperative discussion between the anesthetist and the patient, with some input from the surgical team. This decision is affected partly by the medical condition of the patient, though there remain questions regarding whether and to what extent regional and general anesthesia are significantly different with respect to cardiovascular outcomes, cognitive function, or mortality.

Results from a large retrospective study indicated that patients undergoing knee or hip arthroplasty have better perioperative outcomes with spinal or epidural anesthesia than with general anesthesia.[14, 15]  The study examined the types of anesthesia designated in 382,236 patient records; 11.1% of the patients received neuraxial anesthesia, 74.8% received general anesthesia, and 14.2% received a combination of these. Although the number of 30-day deaths was small for all three types of anesthesia, it was significantly lower in patients who had the neuraxial or combined forms than in those who received pure general anesthesia (0.10%, 0.10%, and 0.18%, respectively).

Patients who have epidural anesthesia have been shown to develop fewer perioperative deep vein thromboses. Whether this has any overall positive benefit to the patient is not known. Another benefit of epidural anesthesia is the presence of an indwelling catheter for 48-72 hours postoperatively for pain control, which eliminates the need for excessive amounts of centrally acting analgesics.

Adverse effects of continuous postoperative epidural analgesia include the following[16, 17] :

• Pruritus
• Urinary retention
• Nausea
• Vomiting
• Epidural hematoma (rare)

In a study by Shum et al, continuous femoral nerve block for analgesia, compared with no femoral nerve block, resulted in less pain, higher satisfaction, and lower morphine use in patients immediately after TKA.[17] At 2-year follow-up, no significant differences in functional outcome were identified.

IIfeld et al found that a 4-day ambulatory continuous femoral nerve block, using a portable infusion pump, helped decrease time to discharge after TKA.[18] In a multicenter, triple-masked, placebo-controlled study, patients received a continuous femoral nerve block with perineural ropivacaine 0.2% from surgery until the following morning, at which time they were randomized either to continue perineural ropivacaine (n = 39) or to switch to normal saline (n = 38). Time to reaching three predefined discharge criteria (adequate analgesia, independence from intravenous opioids, and ambulation 30 m) was reduced by an estimated 20% in the patients receiving ambulatory analgesia.

Positioning

Afterb preoperative cleaning of the leg, the patient is set up on the operating table in a supine position (see the image below).

Follow-up depends on the surgeon, the patient, and the healthcare system.[19] A typical example would be surgical follow-up appointments at 6 weeks, 3 months, 6 months, 1 year, 2 years, 5 years, 10 years, and thereafter as appropriate. This would be modified for each patient according to age, degree of activity, and presence of complications.

Satisfactory knee function is usually restored after TKA, and the majority of patients are able to return to low-impact sporting activity.[20, 21] Long-term studies have confirmed satisfactory functional scores and shown a 91-96% prosthesis survival rate at 14-15 years of follow-up. No difference has been established between PCL-retaining and PCL-substituting designs. Cementless designs have not had the same length of follow-up, but studies at 10-12 years have reported a 95% prosthesis survival rate.[6, 9, 10, 22, 23]

Total knee arthroplasty (TKA) should be performed in a laminar-flow operating theater with meticulous attention to detail in order to prevent contamination of the operative site.

A thigh tourniquet is generally used to aid surgical exposure, though it should be avoided in patients with a history of previous deep vein thrombosis (DVT) or significant vascular disease. There remains some debate regarding whether the use of a tourniquet provides significant net benefit.

In a meta-analysis by Jiang et al, the use of a tourniquet significantly reduced intraoperative blood loss, transfusion rate, and operating time (though not postoperative blood loss, measured or calculated total blood loss, transfusion volume, incidence of pulmonary embolism [PE], or length of hospital stay).[24] The authors concluded that the current evidence did not permit definite recommendations either way. In a Danish study, the use of a tourniquet in primary TKAs did not significantly increase the risk of VTE within 90 days.[25]

Antibiotics and antithrombotic prophylaxis are administered approximately 30 minutes before the incision is made. Mechanical antithromboembolic devices (eg, stockings, foot pumps) are used intraoperatively.

The knee joint is usually approached anteriorly through a medial parapatellar approach, though some surgeons use a lateral or subvastus approach. Osteophytes and intra-articular soft tissues are then cleared.

Bone cuts in the distal femur are made perpendicular to the mechanical axis, usually with the help of an intramedullary alignment system, which is then checked against the center of the hip. The proximal tibia is cut perpendicular to the mechanical axis of the tibia with the help of either intramedullary or extramedullary alignment rods. Restoration of mechanical alignment is important to allow optimum load sharing and prevent eccentric loading through the prosthesis.

Sufficient bone is removed so that the prosthesis recreates the level of the joint line. This allows the ligaments around the knee to be balanced accurately and prevents alteration in patella height, which can have a deleterious effect on patellofemoral mechanics.

Because of preoperative deformity, some ligaments around the knee are contracted. These are carefully released in a stepwise fashion to balance the soft tissues around the knee and allow optimum knee kinematics (see the image below).

Patellofemoral tracking is assessed with trial components in situ and balanced if necessary with a lateral release or medial reefing procedure. If the patellofemoral joint is significantly diseased, it can be resurfaced with a polyethylene button. The original width of the patella must be recreated.

Once the definitive components have been selected, they are cemented into place with polymethyl methacrylate (PMMA) cement. If an uncemented system is being used (see the first image below), press-fit and bony ingrowth provide the short-term and long-term fixation of the component (see the second image below).

The tourniquet should be deflated before closure to allow accurate hemostasis. The knee joint is usually drained and dressed in extension. There is some evidence in favor of performing surgical wound closure with the knee in flexion.[26, 27, 28] Foot pulses are checked at the end of the procedure.

In a double-blind study of 48 patients undergoing TKA, Essving et al reported that local infiltration analgesia, started during operation, yielded excellent postoperative pain relief.[29] Patients in the treatment group received a periarticular injection of 400 mg ropivacaine, 30 mg ketorolac, and 0.5 mg epinephrine during surgery and an intra-articular injection of 200 mg ropivacaine, 30 mg ketorolac, and 0.1 mg epinephrine 21 hours postoperatively. Patients in the placebo group received a postoperative injection of saline. Overall, the treatment group had less postoperative pain, used less morphine, fulfilled discharge criteria more quickly, and had higher patient satisfaction.

In a pair of retrospective analyses reported at the 2014 annual meeting of the American Academy of Orthopaedic Surgeons (AAOS), Emerson et al found that extended-release bupivacaine was as effective as femoral nerve block for relieving pain in patients who had undergone TKA.[30] Patients treated with bupivacaine extended-release liposome injection also used less narcotic rescue medication, had shorter hospital stays, and sustained fewer falls. A 2015 study by Barrington et al yielded similar findings.[31]  Infiltration technique has been described by Connelly et al.[32]

In a trial comparing continuous catheter femoral nerve block (cFNB) with single-injection femoral nerve block (sFNB) for relief of pain after TKA, Dixit et al found that the two techniques were equivalent with regard to pain relief and that there were no significant differences in opioid consumption, length of hospital stay, outcomes of physical therapy, or associated side effects.[33]

A randomized controlled study by Singh et al found instillation of ropivacaine cocktail and tranexamic acid instillation to be useful and effective for reducing postoperative pain and blood loss after knee arthroplasty.[34]

After the procedure, the patient undergoes recovery and is usually observed for a 24-hour period in a high-dependency ward. Adequate hydration and analgesia are essential in this time of high physical stress. Analgesia is provided through continuation of the intraoperative epidural, patient-controlled intravenous (IV) analgesia, or oral analgesia. Cryotherapy is used to reduce postoperative swelling and pain.

At this early stage, the patient begins knee movement, sometimes using a continuous passive motion (CPM) machine and exercises. These are continued under the supervision of a physiotherapist until discharge.[1, 2] A randomized clinical trial by Labraca et al found that commencing early movement in the first 24 hours after surgery allowed early mobilization and quicker discharge from the hospital.[35]

Drains are usually removed within 24 hours, and the patient is encouraged to walk on postoperative day 2. Continual improvement is generally observed, and discharge occurs in 5-14 days.

Discharge is recommended only once wound healing is satisfactory, knee flexion of 90º has been achieved, the patient is considered to be safe and supported in the home environment, and no complications are present. Thromboembolism prophylaxis is often continued at home for a period of time. The first outpatient review generally is in 6 weeks to 3 months (see the image below).

Approximately 1 of every 30 patients undergoing total joint arthroplasty will require critical care services. In patients at increased risk for using critical care services, early postoperative care in a high-intensity nursing ward has been shown to be beneficial.[36]

Overall mortality with TKA is lower than 1%, but this figure increases with age, male sex, and the number of preexisting medical conditions. Identification and optimization of such conditions preoperatively is important for reducing perioperative complications.[6, 9, 10]

Complications of TKA include the following:

• Thromboembolism
• Infection
• Patellofemoral complications
• Neurovascular complications
• Periprosthetic fractures
• Aseptic loosening
• Arthrofibrosis

Thromboembolism

Thromboembolism includes DVT with subsequent life-threatening PE. Predisposing factors for increased risk of DVT include the following:

• Age older than 40 years
• Female sex
• Obesity
• Varicose veins
• Smoking
• Past history of DVT
• Diabetes mellitus
• Coronary artery disease

The overall incidence of DVT following total knee replacement without any prophylaxis has been reported at 40-88%. Most of these are calf thromboses. The risk of fatal PE, however, is the important figure and is in the range of 0.1-1%.

Many current methods of DVT prophylaxis are available and are used,[37] including mechanical compression stockings or foot pumps and pharmaceutical agents (eg, low-dose warfarin, low-molecular-weight heparin [LMWH], rivaroxaban, and aspirin[38] ). Many studies show evidence of reduction of rates of DVT, but how this affects overall death rates from PE is unclear at this time, with many of the current studies concluding after only 10 days.

Using a multifactorial approach to prevent DVT is probably prudent. Elements of such an approach may include the following:

• Intraoperative foot pumps
• Epidural anesthesia
• Pharmaceutical agents
• Antithromboembolic stockings
• Adequate hydration
• Early mobilization
• Regular postoperative surveillance

Infection

Prevention of infection in TKA begins in the preoperative examination to exclude intercurrent infection. In the operating room, personnel should be kept to the smallest number possible, and traffic in and out of the room should be kept to a minimum. Use of vertical laminar flow in operating theaters, prophylactic antibiotics, ultraviolet light, body exhaust systems to prevent bacterial shedding, and meticulous and expeditious surgery all help to reduce the occurrence of infections to fewer than 1% of operations performed.

The following factors are associated with a higher rate of infection after TKA:

• Rheumatoid arthritis
• Skin breakdown
• Prolonged wound drainage (>6 days)
• Previous knee surgery
• Use of a hinged knee prosthesis
• Obesity
• Concomitant urinary tract infection
• Steroid use
• Renal failure
• Diabetes mellitus
• Malignant disease
• Psoriasis

It has been suggested on theoretical grounds that the use of propofol for general anesthesia in TKA might increase the risk of postoperative periprosthetic infection, in that this agent has a lipid component that supports bacterial growth. However, a study by Kishimoto et al that compared propofol with sevoflurane in this setting did not find the choice of anesthetic agent to have a significant effect on the incidence of post-TKA periprosthetic joint infection.[39]

Treatment of the infected total knee prosthesis often is laborious and time-consuming and a disaster for the patient. The risk is minimized by a theater team obsessed with detail and supported by good nursing skills on the ward and vigilance by the surgeon in the postoperative period.

Negative-pressure wound therapy (NPWT) has been suggested as a potential means of reducing prosthetic joint infection after TKA and total hip arthroplasty (THA), but further study is required to determine its proper role in these settings.[40]

Patellofemoral complications

Patellofemoral complications[41] include patellofemoral instability (see the image below), patellar fracture, patellar component failure, patellar clunk syndrome, and extensor mechanism tendon rupture. All of these complications have been cited as common reasons for reoperation. These can be minimized by attention to detail, meticulous technique, and avoidance of component malposition.

Neurovascular complications

Arterial thrombosis following TKA is a rare (ie, 0.03-0.17%) but devastating complication, frequently resulting in amputation. Several authors have recommended performing TKA without the use of a tourniquet in patients with significant vascular disease. Such patients should undergo a vascular surgery consultation prior to knee replacement.

Peroneal nerve palsy is the most commonly reported nerve palsy after TKA. It usually occurs in the correction of combined fixed valgus and flexion deformities often observed in patients with rheumatoid arthritis. Approximately half of these patients undergo spontaneous recovery, and 50% undergo partial recovery with conservative treatment. Some good results have been obtained with surgical decompression.

Periprosthetic fractures

Supracondylar fractures of the femur are not common after TKA (ie, 0.2-1%). These fractures are observed if the anterior femoral cortex is notched and weakened during surgery and in patients with osteoporosis, rheumatoid arthritis, poor flexion, revision arthroplasty, and neurologic disorders. Treatment is with internal fixation or revision TKA.[42] Although tibial fractures may occur, they are uncommon.

Aseptic loosening

Loosening leads ultimately to failure of the prosthesis and occurs in approximately 5-10% of patients at 10-15 years. It may be complicated by bone loss or osteolysis, which can lead to catastrophic deterioration and make revision surgery difficult. The etiology of this problem is not entirely understood but is related to polyethylene debris causing cellular alterations that result in bone resorption. Once a component is loose, it becomes mechanically unstable with worsening osteolysis. Treatment consists of revision with bone grafting.

A meta-analysis by Mercurio et al found that whereas cemented and cementless fixation yielded comparable functional outcomes and reoperation rates in primary TKA, cemented TKA was associated with less blood loss but a higher rate of aseptic loosening.[8]

Arthrofibrosis

This is a condition of excessive scar tissue causing restriction of knee movement. The etiology is unknown. Athrofibrosis is more common in young patients and in patients taking warfarin. It occurs in fewer than 1% of patients. Conservative management includes anti-inflammatory medication, physiotherapy, and reassurance. More aggressive treatment includes manipulation under anesthetic with CPM therapy and excision of scar tissue.