Total Knee Arthroplasty (TKA), commonly known as knee replacement surgery, is a highly effective procedure designed to relieve pain and restore function in a severely damaged knee joint. Because this is a major operation involving artificial components, an extensive pre-operative evaluation is conducted. This preparation focuses on assessing the damaged joint and confirming the patient’s overall health can withstand the stress of surgery and recovery. The goal of testing is to identify and address any underlying medical conditions that could increase the risk of complications.
Assessing the Knee Joint with Imaging
The foundational test for planning knee replacement surgery is the X-ray, providing a two-dimensional view of the joint’s bony structure. Full-length, weight-bearing X-rays are required to accurately capture the degree of joint space narrowing, the presence of bone spurs (osteophytes), and the overall mechanical alignment of the entire leg from the hip to the ankle. This comprehensive view, often called a Hip-Knee-Ankle (HKA) film, allows the surgeon to measure the precise alignment correction needed for the new joint.
This imaging determines the extent of arthritis damage and helps the surgical team select the correct size and type of implant components. While X-rays are usually sufficient for standard planning, advanced imaging may be used for more complex cases. A Computed Tomography (CT) scan offers a detailed three-dimensional assessment, useful for planning component sizing and position, especially with significant bone deformity or when utilizing robotic surgery. Magnetic Resonance Imaging (MRI) is less common but may be ordered if there is suspicion of soft tissue involvement, such as ligament damage.
Essential Laboratory and Cardiac Screening
A comprehensive set of laboratory tests is required to provide a clear picture of the patient’s systemic health, ensuring the body is prepared for the physiological demands of the procedure. A Complete Blood Count (CBC) measures red blood cells to screen for anemia and white blood cells, which can indicate an underlying infection. Platelet counts are also checked to ensure proper blood clotting function.
The Comprehensive Metabolic Panel (CMP) assesses the function of the kidneys and liver, as these organs process medications and manage fluid balance. This panel also measures blood glucose and electrolyte levels, which must be stable before surgery, especially in patients with diabetes or hypertension. Coagulation studies, such as Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT), evaluate the blood’s ability to clot to minimize the risk of excessive bleeding.
A Urinalysis is routinely ordered to screen for any existing urinary tract infection, as an infection anywhere in the body can spread to the new joint. An Electrocardiogram (EKG) is a standard diagnostic test, especially for older patients or those with a history of heart issues, to assess the heart’s electrical activity and rhythm. The EKG helps ensure the patient’s heart can safely handle the stress of anesthesia and the surgical event.
Pre-Anesthesia and Infection Risk Assessment
Before receiving final medical clearance, all patients undergo a consultation with an anesthesia provider. They discuss the patient’s medical history, current medications, and the specific plan for pain control and anesthesia during the procedure. This discussion focuses on optimizing existing conditions, such as ensuring blood pressure is controlled and asthma is stable, which affects the safe administration of anesthesia. The goal is to create a tailored anesthesia plan that minimizes risk based on the patient’s unique health profile.
A significant focus of the pre-operative workup is reducing the risk of periprosthetic joint infection (PJI). Screening for Methicillin-Resistant Staphylococcus aureus (MRSA) and Methicillin-Sensitive Staphylococcus aureus (MSSA) colonization is common, typically involving nasal swabs. If a patient tests positive, a decolonization protocol is initiated, often involving an antibacterial ointment and special antiseptic body washes.
Dental clearance is a routine requirement because a hidden infection in the mouth, such as an abscess or severe gum disease, can introduce bacteria into the bloodstream that may colonize the new joint. The consensus is that any active oral infection must be treated and resolved before the elective surgery can proceed. Patients with chronic conditions like diabetes or obesity are required to show their conditions are well-managed and stable, as poor control increases the risk of surgical complications and poor wound healing.