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Introduction   

A total knee replacement is a surgical procedure that involves replacing a damaged knee joint with a prosthetic joint. This procedure is a treatment option for patients with severe pain and impaired knee function and have had no success with conservative management. Although knee replacements are performed in patients with different pathological conditions, patients with osteoarthritis are the most common candidates for the procedure.  

There is an estimated annual incidence of symptomatic knee osteoarthritis at 240 per 100,000 patients, with roughly, 400,000 primary knee replacements performed annually in the U.S. (3). 

Total knee replacements are one of the most common orthopedic procedures performed in the U.S. (1). Furthermore, the amount of knee replacements performed every year in the U.S. is expected to increase in volume by 143% by 2050 (2).  

This course provides nurses with a comprehensive review of the indications, contraindications, and management of knee replacements to be better prepared to improve patient outcomes.  

Anatomy of the Knee 

The knee joint is the largest hinge joint in the body. The knee is made up of three bones: the femur (upper leg), tibia (lower leg), and the patella (kneecap). Within the knee, there is an intricate network of tendons, ligaments, menisci, cartilage, muscles, and synovial fluid that work together to stabilize the knee and allow it to move properly. The knee is a weight bearing joint and its primary function is flexion and extension. 

Damage to one or more components of the knee joint can result in pain and impaired function and can be caused by injury or pathological conditions. A knee replacement is a surgical procedure that consists of replacing damaged components of the knee with prosthetic metal and polyethylene parts (3). This procedure is performed by an orthopedic surgeon and recommended when all other conservative measures have proven to be ineffective. 

Conservative measures are injections, physical therapy, orthotic appliances, and medications.  Patients can choose to undergo knee replacement when pain and impaired knee function has affected their activities of daily living substantially. 

Indications  

Indications for total knee replacement are knee pain and impaired function as a result osteoarthritis, inflammatory arthritis, and post traumatic arthritis. Over 95% of patients receiving knee replacements have a history of osteoarthritis (2). Osteoarthritis gradually causes degenerative changes to the knee joint over time. Inflammatory arthritis (rheumatoid, gout, psoriatic) is an indication due to its degenerative nature but has required less knee replacements due to advancements in antirheumatic medications. Posttraumatic arthritis is a form of arthritis caused by injuries from high impact sports and motor vehicle accidents. Additional indications are tumors, sequelae of infection, avascular necrosis, and congenital joint abnormalities. 

Contraindications 

Acute infections in any area of the body can cause delays in knee replacement. While the proper timing to proceed with surgery following antibiotic treatment is not well supported, it is necessary to delay surgery until the patient is infection free (2). 

Neurological diseases that affect the lower extremities are a contraindication and based on the extent of the disease can have a major impact on the success of rehabilitative progress. In patients with peripheral vascular disease, a thorough vascular assessment should be performed prior to a knee replacement. The severity of the disease and if collateral circulation is present will determine if revascularization will precede knee replacement (2).  

In any cases of skeletal immaturity, knee replacements will be delayed. Areas around the knee serve as major sources of the overall maturity of the lower extremity (2). 

If the patient is unable to participate in physical therapy, a knee replacement is contraindicated as participation in rehabilitation guides overall postoperative outcome. 

Other contraindications include noncompliance, morbid obesity, insufficient bone stock, and a medically unstable patient (1). If a patient is unable to have a knee replacement, alternative approaches may be more suitable. Some alternatives to a total knee replacement include partial knee replacement, osteotomy, and joint resurfacing (2). 

Diagnostics 

The Radiographic study most appropriate to view degenerative changes in the knee is an x-ray. X-rays are obtained pre and postoperatively in three basic views. An MRI is less common and used only if pathology is uncertain or an x-ray does not adequately capture degenerative changes (2). 

Preoperative Nursing Assessment and Management 

It is important to assess the patient’s pain characteristics and symptoms when gathering relevant data. A thorough medical history is an essential part of the preoperative nursing assessment. The medical history of all systems assists with identifying co morbidities that may increase the patient’s risk for complications. Additional patient information to collect is medications, allergies, nutrition status, previous conservative measures, past surgical history, family history, social history, support system, and psychological status.  

When conducting a medication reconciliation, emphasis should be placed on opioids, NSAIDS, antithrombotics, and supplements. Depending on the amount and frequency of opioid use, opioids can affect perioperative outcomes by impairing the patient’s ability to achieve pain control. Antithrombotics increase the risk of bleeding and can delay the wound healing process. Certain supplements such as fish oil have properties that can increase the patient’s risk for bleeding (2). Obesity and smoking status should be considered prior to undergoing a knee replacement.  

There are no standard weight recommendations for knee replacements but there is much concern with performing a knee replacement on a patient with a BMI ≥ 40kg/

m2m2

(2). With increased BMI, there is an increased risk for postoperative complications. Smokers are at an increased risk for postoperative complications as well. It is advised that smoking cessation be initiated six weeks before surgery and continue six weeks postoperatively, but long-term smoking cessation is encouraged (2). When compared with non-smokers, smokers showed increased rates of wound complications, deep infection, pneumonia, and reoperation (2). 

Physical Assessment 

The physical assessment involves ensuring that vital signs are in the appropriate range to proceed with surgery. The nurse should obtain a baseline assessment of the patient’s range of motion, circulation, and mobility in the affected extremity.  

Neuromuscular status should be assessed with attention to motor strength and sensation. Inspect the skin for any signs and symptoms of infection, ulcerations, and vascular compromise. Labs should be obtained and reviewed. Some common labs tests ordered prior to surgery include a complete blood count, a comprehensive metabolic panel, and coagulation studies.  

In addition, some patients may require cardiac clearance and an electrocardiogram may be ordered. Patients should receive education on the procedure, expectations, benefits, risks, and outcomes from the surgeon and anesthesiologist. Nurses should ensure that the patient demonstrates understanding and can provide informed consent. 

Postoperative Complications 

Although knee replacements are believed to be safe and successful, complications may arise. The complications can vary from mild to fatal, but efforts should be made to minimize the risks with proper assessment, surgical approach, and careful postoperative management. Postoperative complications include acute and late complications. 

• Acute Postoperative Complications: thromboembolism, blood loss, peroneal nerve palsy, ischemic injury, arterial injury, impaired wound healing, surgical site infection, myocardial infarction, and ligament injury (3) 

• Late Complications: joint instability, patellofemoral disorders, arthrofibrosis, unrelieved pain, and metal hypersensitivity (5) 

Postoperative Nursing Assessment and Management 

Patient assessment postoperatively has few additional considerations. Improved outcomes depend on effective postoperative management which includes pain control, venous thromboembolism (VTE) prevention, reducing complication risks, and mobilization with physical therapy. Additionally, the postoperative physical assessment should include neuromuscular and neurovascular assessment, surgical site inspection, and monitoring postoperative labs and imaging. Safety precautions should be established prior to procedure and reinforced during postoperative period to prevent falls and injury. 

Pain Management 

It is necessary to assist the patient in achieving pain control. Effective pain control facilitates early mobilization and rehabilitation. There are several methods for achieving postoperative pain control that have minimized the need to use intravenous opioids as first line. Some examples are oral opioids, NSAIDs (i.e. ketorolac, gabapentin, regional anesthesia).  

The most commonly used methods of regional anesthesia are single and continuous peripheral nerve blocks and adductor canal blocks. Studies have shown a decrease in perioperative complications and improved patient satisfaction when with peripheral nerve blocks in comparison to the traditional opioid therapy (2). Adductor canal blocks are frequently used due to their association with less muscular weakness which can facilitate mobilization, rehabilitation and decline in falls while in place (2). In some cases, continuous lumbar epidural analgesia may be used.  

VTE Prevention 

Patients are at increased risk of thromboembolism (deep vein thrombosis, pulmonary embolism) which can be fatal without proper prevention. The incidence of deep vein thrombosis following total knee replacement without prevention ranges from 40-88% (2). The type of pharmacological agent used for VTE prevention is determined by performing a risk assessment. Some examples of risk factors related to a knee replacement are duration of procedure, general anesthesia, prolonged immobilization, age, baseline mobility, weight, and any cardiovascular disease. Although major orthopedic surgeries carry a high risk of bleeding, the risk is not so great that pharmacologic VTE prevention should be disqualified unless the patient is not a candidate (2). 

The first line medication used for VTE prevention following a knee replacement is LMWH (low molecular weight heparin or a direct oral anticoagulant) (6). Examples of LMWHs that are most often used enoxaparin or dalteparin. direct oral agents such as rivaroxaban and apixaban are preferred due to increase supportive data of their effectiveness. LMWH should be initiated more than 12 hours before procedure and 12 or more hours postoperatively (6).  

The initial dose of the direct oral anticoagulants should be initiated 6-12 hours or more after surgery (6). Pharmacological VTE prevention should not continue for more than 14 days. Other methods of VTE prevention include mechanical devices such as venous foot pumps and graduated compression stockings. These devices are placed before the procedure and remain in place until discharge. 

Surgical Site Infection Prevention 

An additional postoperative consideration is surgical site infection prevention. Antibiotic therapy is initiated 1 hour before incision. Repeat dosing is not necessary after incision closure and can increase the chances of antimicrobial resistance. However, if antibiotics are used postoperatively, it should be no longer than 24 hours and is determined by factors such as procedure duration and excessive blood loss (2). 

Mobilization  

Physical therapy is an essential part of the success of a knee replacement. A physical therapy regimen that focuses on range of motion, mobility, and muscle strengthening is beneficial to overall outcomes. Range of motion should be performed as early as possible postoperatively. Providing pillow support under the patient’s operative foot helps to prevent contracture. Active and passive exercises coupled with analgesia use can reduce postoperative pain (2). In the absence of complications, patients are usually able to ambulate the same day of surgery with physical therapy if they meet motor and sensory criteria and achieve pain control. Patients will be provided with an assistive device to use and take home upon discharge. 

Outcomes 

The mortality rate from knee replacements is relatively low, ranging from 0.5-1 percent per year. Usually, mortality in knee replacements occurs due to preexisting co-morbidities. Data from the national joint registries shows that 80% of total knee replacements last 25 years. Studies report that the likelihood of requiring a knee revision is high for patients that undergo knee replacements at a younger age. The highest risk (35%) for knee revision found in males between the ages of 50-54 (2). The percentage of patients who experienced prosthetic infection in the first year was nearly 1%. In a survivorship analysis conducted with a sample size of 11,606 knee replacements, prosthetics durability was longer in patients with inflammatory arthritis versus osteoarthritis (2). 

Considerations 

While the goal is to achieve pain control, careful assessment should be made to prevent sedation and respiratory complications when managing pain. Opioid analgesics coupled with a decrease in movement can pose a risk for constipation (3). collaboration with providers, pharmacists, and physical therapists is necessary to ensure the patient’s medications are being managed appropriately and the patient can be mobilized regularly. In addition, nurses should assess and initiate fall precautions in patients of increasing age and on high-risk medications such as analgesics and anticoagulants.  

Nurses should educate patients on proper body mechanics following knee replacements. Education should include not crossing legs, no inward leg movements, no bending over to reach objects and safe ambulation with an assistive device. In addition, patients should be educated on how to rest the operative knee when in bed, pillow should be underneath foot not operative knee to prevent contracture (3).  

For patients who received regional blocks, epidurals, or spinal block, nurses should closely monitor the return of sensation and motor function as the medication works through their system. As a result, some patients may need to demonstrate the ability to urinate before discharge. Patient education should address life-long antibiotic prophylaxis for dental procedures and protocols for travel and radiographic imaging. 

Conclusion

Knee replacements are effective surgical procedures that can improve a patient’s quality of life by providing sustained pain relief and restored function of the knee. A number of pathological conditions can cause degenerative changes in the knee – osteoarthritis is the most common cause and affects millions of people in the U.S. (3). With that in mind, the number of knee replacements are expected to increase, especially as the aging population grows. Perioperative management such as thorough assessment, VTE prevention, pain control, surgical site infection prevention, and optimal rehabilitative measures are necessary to maintain low rates of complication and improve patient care and satisfaction. 

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