Blood Tests Physicians May Recommend Prior To Knee Surgery

by Brent Woods

Before undergoing orthopedic procedures such as robotic-assisted knee surgery or hip replacement surgery, your physician may recommend that you get some important blood tests. This is to help ensure that you are healthy enough to withstand the procedure and to determine if you have any pre-existing conditions that might place you at high risk for surgery. In addition to blood analysis, your doctor may also recommend other lab services such as fluid analysis to see if your knee joint fluid contains any harmful microorganisms. Here are some blood tests you may need prior to your knee surgery.


Your doctor may order a CBC, or complete blood count. This test will evaluate your red and white blood cells, platelets, hemoglobin, and hematocrit. If the doctor also ordered a differential, your neutrophils and eosinophils will also be evaluated to help rule out certain infections or allergies.

There is no special preparation for a complete blood count such as fasting or limiting your intake of water. In fact, your doctor may recommend that you drink plenty of water prior to the test, especially if he or she believes that you may be mildly dehydrated. If you are dehydrated, your blood draw may be more challenging for the lab technician. 

Blood Chemistry Profile

Another blood test your doctor may recommend prior to undergoing orthopedic surgery is a blood chemistry profile. This test helps evaluates liver and kidney function, and can determine if your electrolytes, such as potassium are abnormal. If your potassium levels are too high or too low, it may indicate cardiovascular or blood pressure problems.

If your doctor determines that your potassium levels are critically abnormal, he or she may delay your knee surgery until further testing has ruled out serious health problems. Unlike a complete blood count, you will be required to fast prior to having your blood drawn for your blood chemistry profile. If you eat or drink anything but water, your glucose, potassium, sodium, and even cholesterol levels may be skewed. If this happens, you may need to have a repeat blood chemistry profile drawn.

Talk to your surgeon about which types of blood tests he or she recommends prior to your orthopedic procedure. After evaluating your blood tests, your doctor may feel more confident scheduling your surgery. It is important to note that not all abnormal blood test results will result in the cancellation of your surgery.