Total Knee Arthroplasty
Julie Wong and Michael D. Ries
Introduction
Osteoarthritis (OA), also called osteoarthroses or degenerative joint disease, is the most common type of arthritis and one of the leading causes of disability worldwide. OA is a chronic condition characterized by the breakdown of the joint’s cartilage. Cartilage is the part of the joint that cushions the ends of the bones and allows easy movement of joints. The breakdown of cartilage causes the bones to rub against each other, causing stiffness, pain, and loss of movement in the joint. In the United States, it is estimated that OA may affect 33 million adults.1 When conservative management fails to decrease pain or restore mobility, surgical intervention becomes the treatment of choice. Arthroscopic surgeries may be beneficial in early stages with mechanical symptoms,2 but when this also fails, a total knee arthroplasty (TKA) is usually recommended.
According to the American Academy of Orthopaedic Surgeons, approximately 581,000 knee replacements are performed each year. Most were performed on people aged 60 to 80,3 reflecting the aging population of Baby Boomers. Understanding the surgical procedure of the TKA and designing appropriate programs for rehabilitation are essential to ensure successful and cost-effective outcomes in anticipation of this future growth. Self-report measures of perceived functional ability indicate that 1 year following TKA, individuals have regained 80% of normal functions. However, despite improvement compared with preoperative status, pain and stiffness can remain a problem for some of these people.4
The scope of this chapter focuses on primary TKA. It is referred to as TKA, rather than total knee replacement (TKR), to distinguish it from total knee revision (which is also referred to as TKR). In addition, minimally invasive surgery (MIS)-TKA is also described.
Surgical Indications And Considerations
TKA is an effective treatment for symptomatic OA or inflammatory arthritis of the knee that is not responsive to conservative therapy. Earlier stages of arthritis may be treated with nonsteroidal antiinflammatory drugs, activity restrictions, exercise, bracing, orthotics, and weight loss. Other treatments include injections of hyaluronic acid or cortisone. However, when conservative measures fail and arthritic symptoms limit functional activity, surgery is a more appropriate treatment option. If symptoms are mechanical and associated with catching or locking more than weight-bearing pain, they may result from a torn or degenerative meniscus. Magnetic resonance imaging (MRI) is useful to delineate meniscal pathology from degeneration of the articular cartilage. Arthroscopic débridement may be beneficial for treatment of meniscal pathology but does not appear to be as helpful for management of articular cartilage degeneration.5 If cartilage degeneration occurs primarily in the medial tibiofemoral (TF) compartment with varus deformity, then valgus osteotomy of the tibia can be effective in relieving medial-sided knee pain and delay the need for total joint replacement.6 Osteotomy is most appropriate for treatment of unicompartmental OA in a young active patient, a knee with adequate range of motion (ROM), and limited varus deformity. Relative contraindications include obesity, flexion contracture, significant lateral compartment or patellofemoral arthritis, TF subluxation, and advanced age. For lateral compartment OA with valgus deformity, distal femoral rather than proximal tibial osteotomy is preferred. However, osteotomy generally requires a longer rehabilitation period, and outcomes are less predictable than for TKA.7
Prosthetic options include metallic interposition hemiarthroplasty, as well as unicompartmental, bicompartmental, and TKA. The McKeever and MacIntosh metallic interposition hemiarthroplasties were used before the development of TKA.8,9 The implant is a metallic spacer placed between the femoral and tibial surfaces. Favorable results may be achieved most commonly in a patient with arthritic changes in one compartment who was not considered an appropriate candidate for osteotomy because of obesity, limited motion, or arthritic involvement of the opposite compartment.10,11 However, pain may develop from articulation of the joint surface with the metallic implant. More recently a mobile metallic Uni spacer* has been used which is intended to distract the medial compartment and transfer loads to the lateral compartment.12 However, results appear less predictable than unicompartmental or TKA.
Unicompartmental, bicompartmental, and TKA resurface both the femoral and tibial articular portions of the joint and are effective in relieving arthritic pain. Unicompartmental arthroplasty is indicated for degenerative arthritis limited to either the medial or lateral TF compartment with preservation of the opposite TF and patellofemoral (PF) compartments. Unicompartmental arthroplasty preserves both cruciate ligaments, the opposite TF compartment, and the PF joint, which is typically associated with more favorable knee kinematics, ROM, and overall joint function than TKA. However, failure of unicondylar arthroplasty may occur from the development of arthritic symptoms in the PF or opposite TF compartment, requiring conversion to TKA. Mechanical failure or polyethylene wear may also limit the longevity of unicondylar replacement. Although the indications for use of unicondylar replacement as an alternative to TKA are controversial, unicondylar replacement is generally considered less predictable in terms of longevity of the arthroplasty, particularly when used in situations in which some arthritic involvement of the opposite TF or PF compartment exists. Recent literature shows favorable functional results and patient satisfaction from unicompartmental knee arthroplasty (UKA), especially in the younger, high-demand, and active patients.13 The advantages of UKA versus TKA include better ROM at discharge and a shorter hospital stay (77° versus 67° and 1.3 to 1.4 days versus 2.2 days). The average arc of motion at initial 6-week follow-up was 116° for the UKA patients and 110° for the TKA patients, with 56% of knees having greater than 120°. Early discharge for the patients appeared to be safe; in 97% of cases, patients were discharged directly to home, but 18% of the cases required home health physical therapy and 76% of the cases required outpatient physical therapy. Only 3% of the patients required a skilled nursing or postdischarge rehabilitation stay.14
Bicompartmental (combined medial and PF) arthroplasty is indicated for treatment of symptomatic medial compartment and PF OA.15 Early results with bicompartmental arthroplasty indicate that satisfactory clinical results and restoration of normal kinematics can be achieved.16 However, since bicompartmental arthroplasty is a relatively new procedure, long-term results are not known.
TKA is an effective treatment for severe arthritic knee pain. Both the medial and lateral TF, and usually the PF compartments, are resurfaced in TKA. After TKA, reliable improvement in pain and function can be expected, and survivorship rates of 90% to 95% after 10 years have frequently been reported.17–22 
Early failures may result from infection, instability, malalignment, stiffness, reflex sympathetic dystrophy, and patellar problems. Relative contraindications include active infection, extensor mechanism disruption, severe loss of bony or ligament support, and uncontrolled cardiac disease or medical comorbidities that substantially increase the risk of perioperative morbidity and mortality. However, using proper surgical technique, implant selection, appropriate postoperative pain management, and rehabilitation can avoid these problems. Recent developments including computer-assisted surgery, more kinematic or high-flexion implant designs, use of MIS, and MRI-derived custom cutting blocks may further improve the results of TKA. TKA performed through a conventional skin incision centered over the rectus tendon proximally and extending distal to the tibial tubercle, with a medial parapatellar arthrotomy, is associated with reliable pain relief, improvement in function, and 90% to 95% 10-year survivorship.17–22 However, many patients experience significant pain and inflammation, which typically occurs to some extent for 6 months after arthroplasty and may limit participation in rehabilitation exercises. Less invasive or MIS permits TKA to be performed with reduced soft tissue trauma, with average skin incision of 9.4 to 10.9 cm in the MIS group and 13.7 to 17.1 cm in the conventional group.23 Reports indicate that MIS is associated with less blood loss, less pain, and earlier return of quadriceps function and ROM.24–26
Recent literature shows favorable results in the MIS surgery. In selected patients, the Berger and associates’ study showed that outpatient MIS TKA was safe for discharge on the day of surgery with no short-term readmission or complications in 96% of the patients.27 In Tanavalee’s study, 82% of the MIS patients were able to do active knee extension on day 1 while none were able to do active knee extension in the conventional group. Additionally, patients who could walk on day 1 were 17 versus 2.23 In another study, in the first 12 weeks after surgery, the MIS group had less flexion contracture and better flexion.28 At 1 year postoperative, average passive range of motion was 131° in the MIS group and 121° in the conventional group; while active range of motion was 125° in the MIS group and 115° in the conventional group.29
However, a minimally invasive approach may compromise surgical exposure and result in increased complications. With use of small cutting blocks and avoiding dissection of the suprapatellar pouch, reliable results can be achieved with a complication rate that is not greater than conventional TKA.24–26 Particularly, when combined with a preoperative patient education program and multimodal postoperative pain management, TKA performed through a minimally invasive approach appears to offer advantages compared with conventional TKA. However, more muscular patients, those with prior surgery, stiffness, poor skin vascularity, or significant deformity requiring soft tissue releases may not be appropriate candidates for a minimally invasive approach.
Surgical Procedures—Traditional
Preoperative Evaluation
Preoperative evaluation always includes a thorough history and physical examination, determination of the type of arthritis, other joint involvement and functional status, walking distance, current and expected activity level, and sports involvement. Other significant concerns include history of deep venous thrombosis (DVT) or pulmonary embolus (PE) and previous surgery such as joint replacement, corrective osteotomy, and internal fixation of a hip, femur, or tibial fracture. Close attention is paid to joint alignment (varus or valgus), stability, ROM (especially the presence or absence of flexion contracture), muscle tone, and leg lengths.
Preoperative radiographs should include long weight-bearing films to demonstrate any femoral or tibial deformity and aid in determining overall lower extremity (LE) alignment. The angle between the mechanical and anatomic axis is measured on the femur to ensure that the distal femoral osteotomy will be perpendicular to the mechanical axis and parallel to the proximal tibial osteotomy (Fig. 27-1). Routine roentgenograms should also include anteroposterior (AP) standing films, as well as lateral and patellar views.
Procedure
Numerous implant and fixation choices are available for TKA:
1 Cemented, uncemented, or hybrid fixation
2 Metal-backed tibia or all-polyethylene tibia
The technique described here is the primary TKA using cemented fixation, a metal-backed tibia, an all-polyethylene patella, and posterior cruciate substitution (Fig. 27-2). Currently, this combination is the most commonly used with consistent long-term results published to date.30–34
Surgical Technique
An antithrombotic stocking or pump is placed on the uninvolved leg. The patient is questioned as to which knee is to be replaced as a final check to avoid the mistake of operating on the wrong knee. An intravenous antibiotic, usually first-generation cephalosporin, is given before the skin incision is made. The patient is placed supine on the operating room table with a tourniquet about the proximal thigh. A general endotracheal or regional anesthetic is required. However, peripheral nerve block of the femoral nerve has been shown to be effective in controlling pain whether through a local infusion (24 hours) or administered via percutaneous insertion of a catheter adjacent to the femoral nerve (a 2- to 3-day ambulatory continuous femoral nerve block).35,36
A sandbag is taped to the operating room table, or a commercial leg-holding device is often used to help stabilize the leg during the procedure. The entire LE is sterilely prepared and draped. The LE is exsanguinated with an Esmarch bandage, and a tourniquet is inflated to an appropriate pressure.
Exposure
A longitudinal midline skin incision is made extending from proximal to the patella to just distal to the tibial tuberosity. Full-thickness skin flaps, including the deep fascia, are developed medially and laterally (Fig. 27-3). A medial arthrotomy is made extending from the quadriceps tendon and ending medial to the tibial tuberosity. The patella is everted or subluxed laterally. After flexing the knee to 90°, the surgeon trims osteophytes from the femoral condyles, intercondylar notch, and tibial plateaus. The cruciate ligaments are excised.
Ligament Balancing
Ligamentous balance is addressed by inserting spreaders in the medial and lateral femoral tibial joints, both in flexion and extension. Equal spacing is then attained by excision of osteophytes and soft tissue releases. The three most common deformities encountered are varus, valgus, and flexion. Release of contracted soft tissues on the concave side of the deformity is achieved either by sequential subperiosteal longitudinal release of individual anatomic soft tissue constraints or use of multiple transverse stab wound incisions (pie crusting) into the contracted soft tissues.
Varus Deformity.
Osteophytes protruding off the medial tibia are removed and the medial capsule is incised. If necessary, then the medial collateral ligament is subperiosteally stripped off the tibia. For deformities with combined varus and flexion contracture, release of the semimembranosus insertion is often necessary.
Valgus Deformity.
A lateral retinacular release is commonly required. If the valgus deformity is more rigid in extension than in flexion, the iliotibial band is released. The popliteus tendon, lateral collateral ligament, and posterolateral capsule may also be released, depending on the severity of the deformity. Peroneal nerve neuropraxia can occasionally occur, especially with correction of flexion contracture in association with valgus deformity.
Flexion Deformity.
Excising posterior femoral osteophytes and releasing posterior capsular adhesions usually address a minor contracture. Further correction requires resection of more bone from the distal femur and posterior capsular release.
Osseous Preparation.
An intramedullary femoral guide is placed through a drill hole in the center of the trochlea (Fig. 27-4). The intramedullary rod must parallel the femoral shaft in both the AP and lateral planes, ensuring placement parallel to the anatomic axis of the femur. Cutting guides are attached to the intramedullary guide to allow precise osteotomies of the anterior and distal femur. The distal femoral osteotomy is usually made 6° to the anatomic axis to produce distal femoral alignment perpendicular to the mechanical axis (Fig. 27-5).
Either intramedullary or extramedullary tibial cutting guides are used. The proximal tibia is osteotomized with a sagittal saw perpendicular to its long axis, approximately 5 mm distal to its articular surface, and angled posteriorly approximately 3° to 5°. Small tibial defects are effectively addressed with cement. Larger defects require either bone grafting or metal augments.
An AP measuring guide is used to determine the appropriate size and position of the femoral component. An AP cutting block is placed to remove the anterior and posterior femoral condyles. This affords excellent visibility and access to remove any remaining meniscus, cruciate ligament, and osteophytes (Fig. 27-6).
The flexion and extension gaps are measured with standardized spacer blocks. Ideally, the same gap has been produced between the distal femur and tibia in extension and posterior femur and tibia in flexion. This ensures proper soft tissue tension and ligamentous balance. 
If full extension is not attained, then further bone is removed from the distal femur. For very severe flexion contractures, such as those encountered in some cases of hemophilic arthropathy or juvenile rheumatoid arthritis, resection of the distal femur to the level of the collateral ligament insertions may be required. Further bone resection is a relative contraindication to conventional TKA if the ligament insertions are compromised, and use of a more highly constrained or revision prosthesis is necessary. A guide is then used to chamfer the anterior and posterior femoral condyles and remove bone from the intercondylar notch (Fig. 27-7).
Sizing guides are used to determine the proper-sized tibial component.
After orienting the guide in the AP, medial, and lateral planes, the surgeon ensures proper rotation with the use of an alignment rod extending to the middle of the ankle joint. A bone punch is then used to compress the soft cancellous bone in the tibial metaphysis to accommodate the keel on the tibial component (Fig. 27-8). Trial tibial and femoral components are placed to ensure proper sizing, soft tissue tensioning, ligamentous balance, patellar tracking, and ROM.
Patellar thickness is measured with a caliper. The articular surface is removed with a power saw or reamer. A guide is used to drill one or more holes in the patella for additional peg fixation (Fig. 27-9). The component is usually placed slightly medial on the patella to assist in patella tracking. The thickness is again checked with the caliper; if the patella is thicker than before resection, then more patella is removed to restore normal patella thickness. Patella tracking is observed (Fig. 27-10) and if the patella tracks laterally, then a lateral retinacular release is performed. Efforts are made to preserve the superior lateral geniculate artery, thereby preserving the blood supply to the patella.
All trial components are removed, bony surfaces are cleansed with pulse lavage, and bone cement is mixed. All components may be cemented at one time, or a second batch of cement may be prepared to allow sequential implantation of the components. All excess cement is trimmed while soft. After the cement has hardened, the tibial spacer may be exchanged to allow final adjustments with regard to ROM and stability. The tourniquet is released and bleeding controlled.
The wound is irrigated thoroughly and closed over a suction drain. A sterile dressing is applied. An antithrombotic stocking or compressive dressing is applied over the sterile dressing (Fig. 27-11).
Minimally Invasive Surgery
Surgical Technique
The minimally or less invasive skin incision extends from the superior pole of the patella to the tibial tubercle (Fig. 27-12). In most patients the length of the incision is approximately 10 to 12 cm, but it may be longer or shorter depending on the size of the patient. Full-thickness skin and subcutaneous tissue flaps are raised to mobilize the skin and subcutaneous layer and permit adequate deep exposure.
Either a medial parapatellar, midvastus, or quadriceps-sparing (subvastus) arthrotomy may be used to expose the knee. Excellent results have been reported using the minimidvastus approach, whereas the quadriceps-sparing approach is more restrictive and may only be appropriate for thin patients with mobile extensor mechanisms and no intraarticular deformity. Typically for muscular male patients, either more proximal dissection of the vastus medialis (in a midvastus approach) or a medial parapatellar arthrotomy is necessary to displace the extensor mechanism laterally. A portion of the fat pad is excised to facilitate exposure. Lateral patellar subluxation is necessary, but eversion of the patella while the knee is flexed does not necessarily increase exposure and may contribute to quadriceps inhibition and postoperative knee pain (Fig. 27-13). The skin and subcutaneous tissue may be considered as a “mobile window.” By extending the knee, the skin incision is moved more proximally and exposure is centered over the distal femur, whereas flexing the knee permits more distal exposure over the proximal tibia (Figs. 27-14 and 27-15). Cutting guides for MIS-TKA are smaller than conventional instruments but permit accurate bone cuts. Alternatively, custom disposable cutting guides can be used. These are derived from preoperative three-dimensional MRI images of the arthritic knee and intended to provide precise orientation of the bone cuts. With the knee in extension, tension in the extensor mechanism is reduced and the patella may be everted for resurfacing without traumatizing the suprapatellar pouch (Fig. 27-16).
Therapy Guidelines For Rehabilitation
Successful postoperative management of the patient ideally begins preoperatively. In many cases, the patient has already been seen by a physical therapist (PT) for a conservative course of treatment. Prescription of high- and low-resistance training exercises is an essential aspect of management for knee OA and both have significantly improved clinical effects.37 Although the goal of rehabilitation at this time may be to avoid surgery, the PT must bear in mind that the treatment plan is similar to those for preoperative care:
1 Patient education regarding the disease process and prognosis
2 Behavioral and health modification for joint protection
3 Cardiovascular conditioning as an adjunct to weight loss
4 An individualized exercise program to address strength and flexibility issues
Much can be done for these patients in this phase of the disease process. A successful outcome for postoperative TKA can be predicted by the patient’s functional ability and status preoperatively.38–40
In the event that a TKA is the intervention of choice, then preoperative treatment is modified to include the assembly of a multidisciplinary team. This group includes the orthopedic surgeon, PT, nursing staff, occupational therapist, and social service worker. Although each team member is responsible for his or her area of expertise, all are committed to the common goal of providing the best possible care to get the maximal benefit and outcome.
During this phase the patient should be educated and familiarized with the surgical procedure and the phases of the rehabilitation process. This serves both to identify and anticipate any special problems or needs that the patient should incur. It will also reinforce the active role of the patient in his or her own long-term care. Recommendations may involve home planning, dental hygiene, and social planning.
In the era of managed care, many hospitals have formed preoperative educational classes for this purpose. In a group atmosphere, patients can begin to understand the rehabilitation process and formulate realistic goals and expectations. Informational pamphlets outlining all pertinent information are also helpful. Good preoperative care and communication between the team and the patient can guarantee a smooth transition through the postoperative process.
Phase I (Inpatient Acute Care)
TIME: 1 to 5 days after surgery
GOALS: Prevent complications, reduce pain and swelling, promote ROM, restore safety and independence (Table 27-1)
TABLE 27-1
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| Rehabilitation Phase | Criteria to Progress to This Phase | Anticipated Impairments and Functional Limitations | Intervention | Goal | Rationale |
| Phase I Inpatient acute care 1-5 days |
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The goals for this initial period of rehabilitation are standard for any postoperative care. These pertain to the prevention of any possible complications. Medical considerations include (1) the prevention of infection, (2) the prevention of PE, (3) the prevention of DVT, and (4) the reduction of pain and swelling. Functional goals include (1) the promotion of ROM and (2) the restoration of safety and independence in activities of daily living (ADLs) and gait. The treatment plan is formulated with these specific considerations in mind.
Medical Considerations
Intravenous antibiotics are continued for 24 hours. DVT prophylaxis is initiated. This typically consists of antithrombotic pumps, Coumadin, low molecular weight heparin, or a combination of these treatments.
Monitoring the surgical incision for drainage, erythema, excessive pain, or swelling is continued throughout the patient’s stay. 
It is vital for the therapist to be aware of the signs and symptoms of wound infection, as well as other complications such as DVT or PE. If signs and symptoms of possible DVT develop, further knee ROM exercises should be restricted until diagnostic testing is completed and DVT is ruled out or an appropriate level of anticoagulation therapy is achieved. Specific signs, symptoms, and tests are discussed in the Troubleshooting section of this chapter. Any symptom must be brought to the immediate attention of the nursing staff and surgeon.
Functional Considerations
Restoration of functional ROM is essential for the success of TKA. Continuous passive motion (CPM) has been used and shown to be beneficial in regaining early mobility, but may not necessarily affect the final ROM achieved. CPM can be initiated immediately after surgery in the recovery room.
In one study, CPM patients were able to achieve 90° of flexion in 9.1 days versus their non-CPM counterparts, who required 13.8 days to reach the same goal.41,42 Unfortunately, CPM was found to be ineffective in the enhancement of knee extension.41,43
Many surgeons choose to begin immediate postoperative CPM.44,45 Because of wound concerns, others choose to begin on postoperative day 2.46 The beneficial effects of CPM include the improvement of wound healing,47 accelerated clearance of hemarthrosis,48 reduced muscle atrophy,49,50 reduced adhesion formation,51–54 reduction in the incident of DVT,55 decreased hospital stay,56 and decreased need for medication.57,58 Although excellent function and ROM can be achieved without the use of CPM, many surgeons and patients find that CPM is useful in reducing the frequency of complications after TKA.45,46,59
The protocol of CPM application varies in the literature. In general, the initial settings range from 0° to 25° to 40° of flexion. The range is then either increased 5° to 10° per day or to patient tolerance. CPM can be used from 4 to 20 hours per day. Its use is discontinued at the end of the acute hospital stay or when maximum knee flexion of the CPM machine is attained.
Another modality that has been shown to be useful in improving ROM and quadriceps strength is neuromuscular electrical stimulation (NMES). 
Mitigating quadriceps muscle weakness immediately after TKA using early NMES may improve functional outcomes, because quadriceps weakness has been associated with numerous functional limitations and an increased risk for falls.60 When NMES was added to a voluntary exercise program, deficits in quadriceps muscle strength and activation resolved quickly after TKA.61 In conjunction with the CPM, the application of NMES was shown to reduce extensor lag and the length of stay in the acute care setting.59
Exercises are taught at bedside beginning on postoperative day 2 or 3.44,62 Breathing exercises promote full excursion of the rib cage. Ankle ROM exercises (i.e., pumping, circumduction) along with instruction in proper elevation and positioning of the LE is encouraged (Fig. 27-17). The purpose of these exercises is to engage the muscle pump and passive gravity feed to decrease distal edema and avoid DVT.
