Preparing for Knee Replacement: The Tests and Medication Checks Your Team Orders First

The letter arrives with a surgery date circled, and underneath it a second page nobody expected: a list of appointments before the appointment. A blood draw. A heart tracing. A nurse who wants to see every pill bottle in the bathroom cabinet. For many people about to prepare for knee replacement surgery, this is the moment the operation stops feeling abstract and starts feeling like a project.

It helps to know that the list is not bureaucracy. Each test answers a specific question the anesthetist and surgeon need settled before they can safely put a new joint into a leg, and several of them can uncover something fixable while there is still time to fix it. Low iron, a quietly high blood sugar, a tooth that has been grumbling for months: any of these can change the plan.

This explainer walks through what your team is likely to order, why, and what the honest evidence says about the parts of preparation you control.

Preparing for knee replacement surgery starts at the pre-assessment visit, not on the operating day

Pre-assessment, sometimes called pre-admission or pre-operative clinic, is a visit a few weeks before surgery where a nurse, and often an anesthetist, review your health from head to toe. The knee is almost an afterthought. What they are really asking is whether your heart, lungs, kidneys and blood can tolerate an anesthetic and a procedure that involves cutting bone.

The visit has two jobs. The first is to make the anesthetic itself safe: checking your airway, your breathing, your previous reactions to anesthesia and any family history of problems. The second is to lower the odds of complications afterward, which is where most of the test ordering comes from. Anemia, poorly controlled diabetes and untreated infection each raise the risk of a slower or complicated recovery, and each can be improved before the day if it is spotted early. Mayo Clinic describes this visit as the point where your surgeon and anesthesia team gather the information that shapes the plan for the operation.

Come prepared. Bring every medicine you take, prescribed or not, including inhalers, eye drops, creams, herbal products and vitamins, ideally in their original containers. Bring a written note of allergies, past operations, any episode of a blood clot, and anything unusual that happened during a previous anesthetic. If you use a device for sleep apnea, say so; the anesthetist will want to know.

One more thing worth saying plainly: pre-assessment is also where you can ask questions without the time pressure of the surgical ward. People who arrive with a short written list tend to leave with clearer answers, and the last section of this article offers one you can adapt.

What actually happens during a knee replacement, in plain language

Your knee is a hinge formed by the lower end of the thigh bone (femur), the upper end of the shin bone (tibia) and the kneecap (patella). Cartilage, the smooth tissue that lets bone glide over bone, wears away in osteoarthritis, so the joint grinds, swells and stiffens. A knee replacement, more precisely called knee arthroplasty, does not replace the whole knee. The surgeon shaves away the worn surfaces and caps the ends of the bones with metal components, separated by a durable plastic insert that acts as new cartilage. The back of the kneecap is often resurfaced as well.

Two broad versions exist. A total knee replacement resurfaces the whole joint. A partial (unicompartmental) replacement treats only one worn section, which is an option for a smaller group of people whose damage is confined to one side of the knee. Your surgeon decides which suits your X-rays and examination.

Anesthesia is usually one of two kinds. A general anesthetic puts you fully to sleep. A spinal anesthetic, an injection into the lower back that numbs you from the waist down, is often combined with sedation so you are drowsy and unaware. Cleveland Clinic notes the operation itself typically takes around one to two hours, though your time in the operating suite will be longer because of positioning and anesthesia.

Components are fixed either with bone cement or with a textured surface designed for bone to grow into. Neither is universally superior; the choice depends on bone quality and surgeon judgment. Knowing this outline matters for preparation because several pre-operative checks exist purely to make the anesthetic and the bone work safer.

Who is usually offered a knee replacement, and who is usually asked to wait

Knee replacement is generally considered when arthritis pain limits everyday life, disturbs sleep or restricts walking, and when other measures have been tried without enough relief. The NHS describes it as an option when treatments such as exercise, weight management, walking aids and medicines have not helped sufficiently. Age alone is not the deciding factor; function and pain are.

The people asked to wait are usually those with something that can be improved first. Common reasons include:

• An active infection anywhere in the body, including a dental abscess, a urinary infection or an infected skin patch, because bacteria in the bloodstream can settle on a new implant.
• Blood sugar that is running high, since poor glucose control slows wound healing and raises infection risk.
• A recent heart attack, stroke or a heart rhythm that has not yet been stabilized, which increases anesthetic risk.
• Broken or inflamed skin over the knee, such as an eczema or psoriasis flare, until it has settled.
• Untreated anemia, which is often correctable in the weeks beforehand.

Some pathways also ask people who smoke to stop for a period before surgery, and some ask those with a higher body weight to work with a dietitian first. The evidence here is mixed rather than settled: smoking clearly impairs wound healing, while the effect of pre-operative weight loss on outcomes is less consistent across studies. Reasonable teams will say so, and will frame any delay as a step toward a safer operation rather than a judgment.

Alternatives remain on the table too. Continued physical therapy, bracing, injections and activity modification are all legitimate choices for some people, and a good consultation should mention them. The final decision rests with you and your treating team together.

Knee replacement pre-op tests: what the blood work tells your team

Blood tests are usually the first thing ordered, and each tube has a purpose.

A full blood count measures hemoglobin, the protein in red cells that carries oxygen. Knee replacement involves predictable blood loss, and someone who starts low is more likely to need a transfusion or to feel exhausted afterward. Finding anemia at pre-assessment often means it can be treated, frequently with iron, before the date arrives. The same test counts white cells, which can hint at an infection you have not noticed, and platelets, the fragments that plug bleeding.

Kidney function and electrolytes matter because many drugs used around surgery, including anesthetic agents and pain medicines, are cleared by the kidneys. Knowing your baseline lets the anesthetist adjust the plan and avoid medicines that would strain kidneys already working hard.

A clotting screen is added when you take a blood-thinning medicine, have a personal or family history of unusual bleeding, or have liver disease. Liver tests may be included for the same reason.

Blood glucose and HbA1c, a measure of your average blood sugar over roughly the previous three months, are checked in people with diabetes and increasingly in everyone, since undiagnosed diabetes is common and raises infection risk. A high result may prompt a referral to improve control before surgery.

A group and save (or type and screen) records your blood group and looks for antibodies, so compatible blood is available quickly if needed. A pregnancy test is offered where relevant.

MedlinePlus lists this kind of blood work among the routine pre-operative steps for knee joint replacement. None of the results is a verdict. They are a snapshot that helps the team decide whether to proceed as planned, treat something first, or adjust the anesthetic.

Heart, lung and imaging checks before knee surgery

An ECG, or electrocardiogram, is a painless tracing of the heart’s electrical activity taken with stickers on the chest and limbs. It shows rhythm problems and can reveal evidence of a past heart attack that caused no symptoms. Most people over a certain age, and anyone with heart disease, high blood pressure or diabetes, will have one. An abnormal trace does not automatically mean surgery is off; it usually means the anesthetist wants more information or a cardiology opinion.

An echocardiogram, an ultrasound of the heart, is added when there is a murmur, unexplained breathlessness, or known valve or heart muscle disease. A chest X-ray is no longer routine for everyone and is reserved for people with lung disease or symptoms.

The anesthetist will also ask functional questions that sound casual but are diagnostic. Can you climb a flight of stairs without stopping? Do you snore loudly or wake gasping? Answers help estimate how your heart and lungs will cope, and screen for sleep apnea, which affects how sedatives and pain medicines are used.

Then there is the knee itself. Standing X-rays of the knee, taken while you bear weight, show the true gap in the joint and the alignment of the leg. Long-leg views from hip to ankle help the surgeon plan the angle of the cuts. Some teams add a CT scan when they use computer-assisted or robotic systems that require a three-dimensional model. Johns Hopkins notes that imaging helps the surgeon size and position the components before the day.

You may be asked to repeat some tests if the surgery date moves. Blood results and ECGs have a shelf life, typically a few months, and a fresh set protects you rather than inconveniences you.

The medication check: blood thinners, diabetes drugs and what "hold" really means

The medication review is the part of preparation that most often changes what you do in the final two weeks, and the part where doing your own thing is riskiest. The principle is simple: some medicines increase bleeding during bone surgery, some interact with anesthesia, and some are more dangerous to stop than to continue. Your prescriber and anesthetist balance those, and they tell you exactly what to do. Never adjust anything on your own.

Anticoagulants, medicines that slow clotting such as warfarin or the newer direct oral anticoagulants, and antiplatelet drugs such as aspirin or clopidogrel, are the headline group. Continuing them raises bleeding in the joint; stopping them raises the risk the condition they protect against, such as a heart stent or atrial fibrillation, causes harm. MedlinePlus notes that in the two weeks before knee replacement you may be asked to stop medicines that make it harder for blood to clot, but which ones, and for how long, is an individual decision often made with a cardiologist. Some people are given a temporary injectable alternative instead.

Non-steroidal anti-inflammatories such as ibuprofen and naproxen also affect platelets and are commonly paused. Diabetes medicines are adjusted because fasting changes your sugar, and one class, SGLT2 inhibitors, is often held for a few days because of a rare acid-related complication around surgery. Most blood pressure medicines are continued, though some are skipped on the morning itself. Estrogen-containing hormone therapy may be paused because it raises clot risk.

Supplements count. Fish oil, vitamin E, ginkgo and garlic extracts can increase bleeding; St John’s wort interferes with anesthetic drugs. Declare all of them. Bring the list, ask which to take on the morning with a sip of water, and write the answer down.

Screening for infection risk: skin, teeth, urine and nasal swabs

Infection around an implant is uncommon but serious, because bacteria can form a film on metal and plastic that antibiotics struggle to penetrate. Much of pre-operative screening exists to shrink that risk.

The nurse will look at the skin over and around the knee, and at your feet. Cracks between toes from athlete’s foot, a leg ulcer, an insect bite that has become inflamed, or a psoriasis plaque near the incision line can all delay surgery until treated. Report any new skin break in the days before, even a small one.

Teeth matter more than people expect. Gum disease and dental abscesses release bacteria into the bloodstream, and many teams ask for outstanding dental work to be completed beforehand. The evidence linking dental treatment to fewer joint infections is observational rather than definitive, so this is a precaution, not a proven shield, but it is a low-cost one.

A urine sample checks for a silent urinary infection, which is treated before surgery. A nasal swab looks for Staphylococcus aureus, including MRSA, a strain resistant to common antibiotics, that lives harmlessly in the nose of many people but can cause wound infection. A positive result usually leads to a short course of an antiseptic nasal ointment and body wash before admission; the team will explain the routine.

You will be given an antiseptic wash for the shower the night before and the morning of surgery. One instruction surprises people: do not shave the leg yourself. Razors create micro-cuts where bacteria multiply. If hair needs removing, it is done with clippers in the operating area just before surgery. The NHS includes this among its standard preparation advice. Antibiotics are given into a vein at the start of the operation as a further layer of protection.

What the weeks before surgery usually look like, and what prehab can and cannot do

Timelines vary between centers, but most follow a recognizable shape. The table below summarizes what commonly happens when; your own instructions override it.

Time before surgery	What usually happens	Your part
4 to 8 weeks	Pre-assessment visit, blood tests, ECG, X-rays, infection screening	Bring full medicine list; book dental check; begin stopping smoking; start prescribed exercises
2 weeks	Medication instructions confirmed; anemia or sugar control addressed	Follow prescriber’s hold instructions; set up the home; arrange a helper and transport
1 week	Admission time confirmed; consent discussed	Pack a bag; practice with crutches or walker if supplied; report any illness
Day before	Fasting and washing instructions apply	Antiseptic shower; no shaving the leg; no alcohol
Morning of	Final checks, anesthetic review, skin marking	Take only the medicines you were told to; arrive on time

Prehab, meaning exercise before surgery, deserves an honest word. Strengthening the thigh muscles and practicing getting up from a chair make intuitive sense, and Mayo Clinic recommends learning to use crutches or a walker in advance. Trials, however, show modest and mainly short-term gains in early walking and stair climbing, with little consistent difference in outcomes by six months. So prehab is worth doing for the first weeks of recovery and for confidence, but it is not a reason to delay surgery for months chasing fitness.

Stopping smoking is different. MedlinePlus advises stopping at least a few weeks beforehand, and the mechanism is direct: nicotine narrows small blood vessels and carbon monoxide starves tissue of oxygen, both of which slow wound and bone healing. Alcohol should be kept modest as well; heavy drinking affects anesthesia and clotting.

How to prepare for knee replacement surgery at home: what you will actually need

Walk through your home now as if your right or left knee will not bend past a right angle and you are carrying a walker. That single exercise reveals most of what needs changing.

Start with the floor. Loose rugs, trailing cables and pet toys are the classic trip hazards, and a fall onto a fresh incision is the outcome everyone wants to avoid. MedlinePlus, in its guidance on getting the home ready for knee or hip surgery, suggests clearing walkways and adding night lights between bed and bathroom.

Then think about height. Low, soft sofas are hard to rise from with a stiff, sore knee. A firm chair with arms and a seat that lets your hips sit above your knees helps enormously. In the bathroom, a raised toilet seat, a shower chair and a hand-held shower head make washing safer. Grab bars, if you can install them, are better than towel rails, which are not designed to hold body weight.

If your bedroom is upstairs, many people arrange to sleep downstairs for the first week or two, though stairs are usually practiced with the physical therapist before discharge. Keep the things you use daily at waist height so you are not bending or reaching overhead.

A short shopping list covers most needs:

• Long-handled reacher, shoe horn and a sock aid
• Ice packs or bags of frozen peas, and a towel to wrap them
• Slip-resistant shoes that close without laces
• Prepared meals and a stocked fridge for the first week
• A small bag or apron to carry a phone and charger while using a walker

Finally, people. Someone should be with you for the first few days, and you will need a ride home; you will not be allowed to drive yourself. Sort pet care and any caring responsibilities in advance so recovery is not competing with them.

What not to do before knee surgery: the final 24 hours

The last day is mostly about not doing things, and each restriction has a reason.

Do not eat or drink outside the fasting instructions. Under anesthesia the reflexes that keep stomach contents out of the lungs are switched off, so a full stomach is genuinely dangerous. MedlinePlus notes you may be asked not to eat or drink for six to twelve hours before surgery; many centers allow clear fluids closer to the time, and some give a carbohydrate drink, but only follow the exact instruction you were given. Chewing gum and mints count as intake.

Do not take any medicine that was not on your approved morning list, and do not take a paused blood thinner or anti-inflammatory because your knee hurts. A mistake here can postpone the operation.

Do not shave, wax or use hair-removal cream on the leg. Do not apply lotion, deodorant, perfume or make-up; they interfere with skin antiseptic and monitoring stickers. Remove nail polish and acrylic nails on at least one hand, since the oxygen probe reads through the nail bed. Leave jewelry and piercings at home; metal can cause burns with electrosurgical equipment.

Do not drink alcohol or smoke. Do not stay silent if you feel unwell. A cold, a cough, a fever, vomiting, a flare of a skin condition or a burning bladder should be reported before you set off, even if it feels trivial. Surgeons would rather reschedule than operate into an infection.

And do not plan to drive yourself home or to be alone that first night. Arrange the lift and the company before you arrive, not after. Pack loose clothing, a pair of shorts for physical therapy, your glasses and hearing aids, and the medicine list one more time.

Knee replacement recovery timeline: how many days of rest, and why movement matters more

People often ask how many days of rest are required after a knee replacement, and the honest answer is that modern care is built around the opposite idea. Mayo Clinic describes physical therapists helping people stand and take steps on the day of surgery or the day after. Prolonged bed rest raises the risk of blood clots, chest infections and stiffness, so “rest” now means paced activity with regular breaks, not days lying flat.

The early timeline, drawn from the sources cited here, usually runs like this. Most people go home the same day or within a few days, according to Mayo Clinic, once they can walk with an aid, manage stairs if needed and control pain with tablets. A blood-thinning medicine or compression stockings, sometimes both, are used for several weeks to prevent clots; the type and duration are the team’s call. Physical therapy continues at home or in a clinic, focused on straightening the knee fully and bending it progressively.

Walking aids are typically needed for a few weeks. The NHS suggests many people can drive again at around six weeks, provided they can perform an emergency stop and their team agrees, and return to work somewhere between six and twelve weeks depending on the job. Swelling and warmth around the knee commonly persist for months and are not, by themselves, a sign of trouble.

Improvement is a long curve. Cleveland Clinic notes most people see the bulk of their recovery over six months to a year, with stiffness and strength continuing to improve. None of these figures is a promise; they are typical ranges, and your team will set expectations for your situation.

What speeds things along, as far as the evidence goes, is unglamorous: doing the exercises, icing and elevating, moving every hour while awake, and sleeping enough.

What people often get wrong about preparing for a new knee

Several beliefs come up again and again in pre-assessment clinics, and correcting them changes behavior.

“I should stop all my medicines to be safe.” Stopping the wrong medicine, such as a heart or blood pressure drug or a steroid the body has come to depend on, can be more dangerous than the surgery. Only the prescriber decides what pauses.

“The operation does the work; therapy is optional.” The implant provides the surface; muscles and scar tissue decide how far it bends. Skipping exercises in the first weeks is one of the most common reasons a knee stays stiff.

“A little cold will not matter.” Anesthesia with an active chest infection raises breathing complications, and any infection risks seeding the implant. Report it.

“I am too old” or “I should wait until I cannot walk at all.” Age alone is not a barrier, and waiting until muscles have wasted makes recovery harder rather than easier.

“Rest is recovery.” Covered above, but worth repeating: sitting for hours invites clots and stiffness.

People also ask about the top mistakes after surgery. From the guidance cited in this article, five stand out: skipping or rushing the prescribed exercises; sitting or lying still for long stretches; ignoring new calf pain or breathlessness; letting pain climb so high that exercise becomes impossible, rather than following the pain plan; and returning to driving or heavy activity before the team agrees.

One more misconception concerns implants themselves. They are durable but not permanent; Cleveland Clinic notes most last around fifteen to twenty years, which is part of why surgeons weigh timing carefully in younger people. Preparation is not about perfection. It is about removing the avoidable reasons for a poor start.

Questions to ask your care team before knee replacement

A pre-assessment visit goes better with a written list. These questions are drawn from what people most often wish they had asked; pick the ones that fit your situation and add your own.

• Which of my tests came back outside the normal range, and does anything need treating before the date?
• Exactly which medicines and supplements should I stop, when, and when do I restart them? Can I have that in writing?
• Which medicines should I take on the morning of surgery, and with how much water?
• What kind of anesthetic are you recommending for me, and why?
• Do I need to see a dentist first?
• What are my personal risks, given my heart, lungs, diabetes or weight, and how are you reducing them?
• How will pain be managed in the hospital and at home, and who do I contact if the plan is not working?
• What will you use to prevent blood clots, and for how long?
• How long do you expect me to stay, and what do I need to demonstrate before going home?
• Who arranges physical therapy afterward, and when does it start?
• What symptoms should make me call you, and what number do I use out of hours?
• When can I realistically shower, drive, return to work and travel?
• Are there alternatives to surgery still worth considering in my case, and what happens if I wait?

Take someone with you if you can; two sets of ears catch more. Ask for the name and role of the person coordinating your care so questions later have a destination. If an answer is uncertain, a good clinician will say so and explain what the evidence shows. That candor is a reassuring sign, not a worrying one.

When to call your doctor: red-flag signs before and after knee replacement

Before surgery, contact the pre-assessment team promptly if you develop a fever, a productive cough or cold, vomiting or diarrhea, burning or frequency when passing urine, a new cut, rash or flare of skin disease near the knee, a toothache or gum swelling, or any new chest pain, palpitations or breathlessness. Also call if you have accidentally taken a medicine you were told to hold, or missed one you were told to continue. None of these means the operation is cancelled; all of them need a clinician’s judgment.

After surgery, the signs that need same-day attention are:

• Increasing redness, warmth, swelling or discharge from the wound, or the edges opening
• A temperature above the level your team specified, or shaking chills
• Pain, tenderness or swelling in the calf or thigh, especially in one leg, which can signal a deep vein thrombosis, a clot in a deep leg vein
• Pain that is escalating rather than settling despite the plan you were given
• New numbness, weakness or a foot that drags
• Bleeding that does not stop with pressure, or black stools, if you are taking a blood thinner

Call emergency services immediately, do not wait for a clinic call-back, if you have sudden breathlessness, chest pain, coughing up blood, fainting or a racing heartbeat. These can indicate a clot travelling to the lung, which is treatable but time-critical. The NHS and Mayo Clinic both list clots and infection among the main risks to watch for after knee replacement.

Every decision about how to respond, including whether to come in, adjust medicines or arrange scans, rests with your treating team. Your job is to notice early and to call. Keep the ward or helpline number on the fridge and in your phone before you leave the hospital.

Frequently asked questions

What should I not do before knee replacement surgery?

Do not eat or drink outside your fasting instructions, take medicines your team did not approve, shave the leg, drink alcohol, smoke, or wear lotion, jewelry or nail polish on the day. Do not hide a cold, fever, skin break or dental infection, and do not plan to drive yourself home. Each rule protects the anesthetic or reduces infection risk.

What do I need at home after knee replacement surgery?

A firm chair with arms, a raised toilet seat, a shower chair, cleared floors, night lights, ice packs, slip-resistant shoes and a reacher or sock aid cover most needs. Arrange someone to stay for the first few days, stock easy meals, and plan to sleep on one level if stairs are difficult, as MedlinePlus home-preparation guidance suggests.

Is there a knee replacement checklist at home I should follow before admission?

Yes, and it is worth writing down: confirm which medicines to take on the morning, complete the antiseptic showers, pack loose clothing, glasses and your medicine list, arrange transport and a helper, remove trip hazards, set up ice and a chair at the right height, and report any new illness. Your team’s written instructions take priority over any general list.

What are the top 5 mistakes to avoid after knee replacement surgery?

The five that come up most in mainstream guidance are skipping prescribed exercises, sitting or lying still for long stretches, ignoring new calf pain or breathlessness, letting pain climb so high that movement becomes impossible instead of following the pain plan, and driving or lifting before the team agrees. Each one slows recovery or raises risk.

How many days of rest is required after knee replacement?

There is no fixed number of rest days; modern care is built on early, paced movement. Mayo Clinic describes standing and walking with a therapist on the day of surgery or the next day. You will rest often between activity, but lying flat for days raises clot and stiffness risk. Follow the activity plan your team gives you.

What knee replacement pre op tests are standard?

Most people have a full blood count, kidney function and electrolytes, blood sugar with HbA1c, a blood group and antibody screen, and a clotting screen if relevant, plus an ECG, standing knee X-rays and screening for infection in the skin, urine and nose. Echocardiograms, chest X-rays or CT scans are added when your history or the surgical technique calls for them.

Do I have to stop my blood thinner before knee surgery?

Possibly, but the decision belongs to your prescriber, often together with a cardiologist and anesthetist. Some anticoagulants and antiplatelet drugs are paused for a period because they increase bleeding in the joint; others are continued or swapped for a temporary alternative because stopping is riskier. Never change these medicines on your own.

Why do I need a dental check before a knee replacement?

Gum disease and dental abscesses release bacteria into the bloodstream, which can settle on a new implant. Many teams therefore ask for outstanding dental treatment to be completed first. The evidence linking dental care to fewer joint infections is observational rather than definitive, so it is a sensible precaution rather than a guarantee.

What does the knee replacement recovery timeline usually look like?

Typical ranges from the sources cited here: walking with an aid begins on the day of surgery or the next day, most people go home the same day or within a few days, walking aids are needed for a few weeks, driving often becomes possible around six weeks, work between six and twelve weeks, and most improvement unfolds over six to twelve months.

Should I exercise before knee replacement surgery?

It can help, with realistic expectations. Strengthening the thigh and practicing with crutches or a walker, as Mayo Clinic suggests, makes the first weeks easier and builds confidence. Trials show modest, mainly short-term gains rather than a lasting difference in outcomes, so prehab is worth doing but is not a reason to delay surgery for months.

References

• MedlinePlus – Knee joint replacement
• MedlinePlus – Getting your home ready – knee or hip surgery
• NHS – Knee replacement
• Cleveland Clinic – Knee Replacement

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.