Total knee arthroplasty (TKA), commonly known as total knee replacement, is a highly effective surgical procedure for relieving chronic pain and restoring mobility in patients with severe knee joint damage. The procedure involves replacing the damaged cartilage and bone ends with metal and plastic components. While TKA is generally successful, the long-term outcome depends heavily on the careful selection of appropriate candidates. Surgeons must evaluate a patient’s overall health and unique anatomical factors, as certain risks can lead to catastrophic implant failure or life-threatening complications.
Uncontrolled Systemic Health Risks
Major medical issues affecting the entire body can make a patient ineligible for elective knee replacement surgery because they dramatically raise the risk of mortality or implant failure. The most immediate contraindication is the presence of an active infection anywhere in the body, such as pneumonia or a urinary tract infection. Implanting a knee prosthesis while a systemic infection is circulating creates a severe risk of periprosthetic joint infection, a complication often requiring multiple complex surgeries.
Uncontrolled diabetes mellitus is another significant systemic barrier, primarily due to its impact on healing and infection defense. Surgeons often require patients to optimize their blood sugar, targeting a hemoglobin A1c (HbA1c) level below 8% before the procedure. High blood sugar impairs immune function and microcirculation, leading to poor wound healing and an increased risk of deep surgical site infection.
Severe cardiopulmonary diseases, such as uncontrolled congestive heart failure (CHF) or severe chronic obstructive pulmonary disease (COPD), may prevent a patient from tolerating the stress of major surgery and anesthesia. These conditions elevate the risk of a perioperative stroke or myocardial infarction. Similarly, end-stage organ failure, such as liver cirrhosis or renal disease requiring hemodialysis, compromises the body’s ability to metabolize anesthesia and heal properly, making TKA excessively high-risk until the underlying condition is optimized.
Compromised Local Joint Integrity
Specific physical conditions affecting the knee and surrounding tissues can prevent a successful outcome, regardless of the patient’s general health. A non-functional extensor mechanism, which includes the quadriceps muscle, patella, and patellar tendon, is considered an absolute contraindication. If the patient cannot actively lift their leg before surgery, the knee replacement will not restore that function.
Severe peripheral vascular disease (PVD) in the limb, characterized by poor blood flow, is a serious concern because it directly impedes wound healing and increases infection risk. Untreated arterial insufficiency means the surgical incision may fail to heal, creating an open gateway for bacteria to reach the new implant. Patients with risk factors for PVD are often screened preoperatively to ensure adequate circulation.
Dermatological issues around the knee, such as active skin infections, chronic ulcers, or severe inflammatory conditions like psoriasis, also pose a direct threat to the surgical site. These conditions compromise the soft tissue envelope, increasing the risk of wound breakdown and deep infection. The incision must be made through healthy, intact skin for the best chance of healing.
Inadequate bone stock, often due to severe osteoporosis, complicates the mechanical success of the implant. The replacement components rely on the surrounding bone for secure fixation, and excessively soft bone may not provide sufficient support, leading to implant loosening or periprosthetic fractures. While not an absolute contraindication, severe bone loss requires specialized surgical techniques, such as using cemented components or longer implant stems, to achieve stability.
Non-Adherence to Rehabilitation Protocols
The success of a knee replacement depends highly on the patient’s commitment to a demanding post-operative recovery, including rigorous physical therapy. Lifestyle and behavioral factors that predict poor compliance can disqualify a patient from surgery. Severe obesity, often defined as a Body Mass Index (BMI) over 40, is a major concern because the excessive mechanical load places immense stress on the new joint, increasing the risk of early implant wear and failure. Morbidly obese patients also experience higher rates of infection and wound complications, often struggling to perform the necessary physical therapy.
Active substance abuse, including alcohol and illicit drugs, or uncontrolled severe psychiatric conditions can significantly jeopardize the post-operative course. These conditions impair a patient’s ability to safely manage pain medication, follow instructions, and reliably engage in rehabilitation. Patients with substance use disorders have a significantly increased risk of periprosthetic joint infection and higher rates of revision surgery.
Smoking is another serious modifiable risk factor, as tobacco chemicals compromise blood flow and inhibit natural healing processes. Smokers experience higher rates of wound complications, delayed bone fusion, and a nearly 10% increased rate of reoperation compared to non-smokers. Surgeons typically require patients to quit smoking for a defined period before and after surgery to mitigate these complications. Patients with unrealistic expectations who believe TKA will restore them to high-impact activities, such as running or jumping, may also be ineligible, as this behavior risks early implant failure and leads to profound dissatisfaction.