Blood Tests Before Knee Replacement: What Patients Should Know
- Dr. Mayur Rabhadiya
- 1 day ago
- 4 min read
Blood tests before knee replacement are not simply a hospital formality. They are part of a broader preoperative assessment designed to identify medical issues that could affect anaesthesia, surgery, blood management or early recovery. The exact tests should be selected according to the patient’s age, medical history, medicines, diabetes status, kidney function, the planned anaesthetic and the hospital’s protocol.
For major surgery such as joint replacement, a full blood count is commonly recommended, while kidney function, ECG and other investigations are selected according to the patient and the procedure. Not every patient requires every possible test.
Why are blood tests done before knee replacement?
Preoperative tests help the surgeon, physician and anaesthesia team answer practical questions before surgery: Is the patient anaemic? Are the kidneys functioning adequately? Are electrolytes significantly abnormal? Is diabetes reasonably controlled? Is there a medical issue that should be investigated or optimised before proceeding?
The aim is not to create a long checklist. The aim is to identify relevant risks early enough to manage them properly.
1. Complete blood count: checking haemoglobin and blood cells
A complete blood count or full blood count measures haemoglobin, white blood cells and platelets. Before knee replacement, haemoglobin is particularly important because significant anaemia may affect the patient’s ability to tolerate surgery and may need evaluation or treatment before the planned operation.
An abnormal blood count does not automatically mean that surgery must be cancelled. The significance depends on the degree of abnormality, the cause, the urgency of surgery and the patient’s overall health. The appropriate next step may be repeat testing, iron studies, treatment of a deficiency or further medical assessment.
2. Kidney function and electrolytes
Kidney-function testing usually includes creatinine, estimated kidney function and electrolytes such as sodium and potassium. These results can affect fluid planning, medication choices and anaesthetic decisions. Kidney-function testing is particularly relevant in patients with kidney disease, diabetes, cardiovascular disease, older age or other risk factors for acute kidney injury.
3. Blood sugar and HbA1c
Blood glucose is often reviewed before major surgery, especially in people with known diabetes or suspected poor glucose control. HbA1c gives information about longer-term glucose control. Current guidance does not recommend routine HbA1c testing for every person without diabetes; in people with diabetes, recent HbA1c information is useful and testing may be offered when it has not been checked recently.
The practical purpose is to understand whether diabetes management needs adjustment before surgery rather than to treat one laboratory number in isolation.
4. Clotting tests and other blood investigations
Clotting tests are not necessarily required for every patient. They may be relevant in selected patients, including those with chronic liver disease, bleeding concerns or particular anticoagulant-management questions. Additional tests can be requested when the medical history, medicines or examination suggest a specific need.
What if a blood test is abnormal?
An abnormal result should be interpreted in context. Some abnormalities are minor and do not change the surgical plan. Others may require optimisation before surgery. Examples include treating clinically important anaemia, improving diabetes management, correcting significant electrolyte abnormalities, reviewing kidney function or obtaining medical or anaesthetic clearance when appropriate.
The key message for patients is that an abnormal result does not equal an automatic cancellation. It is a signal to understand the problem and decide whether anything should be corrected before surgery.
Are blood tests the only preoperative tests before knee replacement?
No. Preoperative assessment may also include blood pressure measurement, medication review, ECG, infection screening and additional cardiac or respiratory evaluation when clinically indicated. The patient’s current medicines—especially blood thinners, diabetes medicines, steroids and other important prescriptions—should be reviewed carefully. Medicines should not be stopped without instructions from the treating team.
A broader overview is available in the complete guide to knee replacement surgery in Mumbai.
Why preoperative testing should be patient-specific
The best preoperative assessment is individualised. A healthy patient and a patient with diabetes, kidney disease, heart disease, anaemia or multiple medicines should not automatically receive identical evaluation. The goal is to obtain the information that can realistically influence perioperative care while avoiding unnecessary tests.
For patients who ultimately require surgery, Dr. Mayur Rabhadiya’s knee replacement practice combines patient-specific surgical planning with minimally invasive mini-subvastus robotic knee replacement where clinically appropriate. Learn more about robotic knee replacement in Mumbai.
Frequently asked questions
Do all patients need the same blood tests before knee replacement?
No. The exact testing depends on the type of surgery, age, health conditions, medicines, anaesthetic plan and local hospital protocol.
Can low haemoglobin delay knee replacement?
Clinically important anaemia may need evaluation and treatment before elective knee replacement. Whether the operation is delayed depends on the severity, cause and overall clinical situation.
Is HbA1c required for everyone?
No. HbA1c is particularly relevant for people with diabetes. Routine HbA1c testing is not recommended for every person without diagnosed diabetes.
Does an abnormal blood test mean my surgery is cancelled?
Not necessarily. The result is interpreted together with the patient’s history, examination, medicines and anaesthetic risk. Many abnormalities can be investigated or optimised before surgery.
About Dr. Mayur Rabhadiya
Dr. Mayur Rabhadiya is an Orthopedic & Joint Replacement Surgeon in Ghatkopar, Mumbai. His clinical focus includes knee arthritis assessment, evidence-based non-surgical treatment and minimally invasive mini-subvastus robotic knee replacement when clinically indicated.
Appointments: +91 84249 03913 | +91 96113 30063 | www.mayurajcc.com
