Knee Replacement

Having Tests


Your surgeon will ask you to have some tests. The tests are usually done a few days or weeks before surgery in a lab, your doctor’s office, or the hospital.

To make sure that the operation is as safe as possible, the surgeon will need your health history or clearance from your primary care physician. Clearance is a shortened version of your medical record that includes only the parts of your health history that may affect your surgery.

Ask your doctor’s office to send a copy of your clearance or health history to the surgeon’s office or the facility where the surgery will be done.

Physical Exam

If you haven’t had a physical exam recently, you will need to schedule one.

Lab Tests

A lab technician will take a blood sample and urine sample to make sure you don’t have medical issues that could increase your risk of complications during surgery.

The blood tests you have will depend on your age and any pre-existing medical conditions. Your doctor may request:

  • Complete Blood Count (CBC)
    This test measures the number of red blood cells, white blood cells, and platelets in your body. It’s important that all three are at a healthy level before surgery.
  • Basic Metabolic Panel (BMP)
    This test makes sure that electrolytes, including sodium and potassium, are balanced in your body. Electrolytes are important for your heart and other organs to function normally, and it’s essential that they are within acceptable levels before surgery.
  • Renal (Kidney) Function
    Some medications, including anesthesia, are processed by your kidneys. This test makes sure your kidneys are working properly.
  • Blood Glucose
    This test makes sure that your blood sugar levels are within an acceptable range. It’s an important test for patients with diabetes.
  • Liver Function Test
    Like the kidneys, the liver processes some medications, including anesthesia. This test measures your liver enzymes to make sure they’re within acceptable levels.
    This test measures the ability of your blood to clot.
  • Pregnancy Test
    This test may be required for women of child-bearing age.


X-rays of the knee, usually taken from 3 different angles, will help the surgeon diagnose the problem and plan the operation. If you’re older than 50, have a history of lung disease, or are a smoker, you may also be required to have a chest x-ray to check for lung infections or abnormalities, which can increase the chance of complications with anesthesia.

Electrocardiogram (EKG or ECG)

An EKG helps your doctor see your normal heart rhythm and check for heart disease. Your surgeon will decide whether you need this test.

Pulmonary Function Test

This test is sometimes required for people who have lung disease, symptoms of lung disease, or a history of smoking.