The concept of "prehabilitation" — pre-operative physical preparation — has growing evidence for improving the outcomes of knee surgery. Arriving in better physical condition translates into faster recovery and a lower risk of complications.
Strengthen the Quadriceps
Isometric contractions and low-impact exercises. Reduces the risk of postoperative arthrogenic muscle inhibition (AMI) — the main factor behind stiffness.
Assess and Treat AMI
Pre-existing arthrogenic muscle inhibition should be identified and treated before surgery. In severe cases, surgery may be postponed to protect the outcome.
Maintain Aerobic Activity
Swimming, cycling or walking as tolerated. Maintains cardiovascular fitness without overloading the knee.
Weight Control
Every kilogram of excess weight increases surgical and complication risk. Losing weight before surgery improves the prognosis — especially with knee replacement.
Learn the Post-op Exercises
Practising the isometric contractions, assisted extension and use of crutches BEFORE surgery makes immediate recovery much easier.
Joint Mobility
Maintain or improve the knee's range of motion. Operating with good mobility reduces the risk of postoperative arthrofibrosis.
Often stopped 24h before — risk of perioperative hypotension
Oral antidiabetics / insulin
Adjust with endocrinologist
Metformin: stop 24–48h before. Insulin: dose adjustment on the day of surgery
Supplements and herbal remedies (omega-3, ginkgo, garlic, etc.)
Stop
7–14 days before — several have an antiplatelet effect
⚠ Note: This table is for guidance only. The specific instructions for your medication are set by the anaesthetist at the pre-operative appointment — which takes absolute priority over any general information.
The Day Before and the Day of Surgery
What to Do in the Last 24 Hours
The Day Before Surgery
Wash with antiseptic soap (if advised by the hospital)
Do not shave the surgical area — the hospital will do this if needed
A light meal up to the fasting time indicated
Do not drink alcohol in the preceding 24h
Make sure you have transport home after surgery
Comfortable clothing, ID and documents ready
Try to rest — anxiety is normal
The Day of Surgery
Fasting: solids 6h before, clear fluids 2h before (confirm with the hospital)
Take authorised usual medication with a small sip of water
No make-up, nail varnish, piercings or jewellery
Leave valuables at home
Bring glasses and hearing aids (labelled with your name)
Arrive at the time indicated by the hospital
Confirm a companion is available for discharge
Frequently Asked Questions
Questions About Preparation
Fasting rules vary by hospital and type of anaesthesia, but usually: no solids in the 6 hours beforehand; clear fluids (water, tea without milk) up to 2 hours before. The anaesthetist will give the specific instructions. If in doubt, complete fasting from midnight is the safest rule.
Yes — strongly recommended, at least 4 weeks before. Smoking reduces tissue oxygenation, increases the risk of infection, delays healing and raises the anaesthetic risk. The earlier you stop, the better the outcome. Stopping completely is ideal, but even a significant reduction has benefits.
For most antihypertensives — yes, with a small sip of water, even when fasting. The exception is ACE inhibitors and ARBs (ramipril, losartan, etc.), which many anaesthetists prefer to stop 24h before. Always confirm with the anaesthetist at the pre-operative appointment.
Yes — having a companion available for discharge is mandatory. After general or regional anaesthesia, you cannot drive or be alone for the first 24 hours. For day-case surgery, discharge is conditional on the presence of a responsible adult to accompany you home.
NC
Dr Nuno Camelo Barbosa
Orthopaedic Surgeon · Knee Subspecialist Hospital Lusíadas Porto · Hospital Misericórdia Vila do Conde · Paços de Ferreira
Surgery preparationERAS protocolPre-op
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The pre-operative appointment is the moment to clear up any questions and receive instructions specific to your case. Don't leave any questions unanswered.