By Kaushalya Hospital | Medically reviewed by a consultant orthopaedic surgeon
If both knees need replacing, you can have them done on the same day, called simultaneous bilateral knee replacement, or as two separate operations weeks to months apart, called staged. Same day means one anaesthetic, one hospital stay and one recovery. Staged means two of each, but published data shows a lower risk of blood clots and death. For younger, healthier patients, the same day is often reasonable. For older patients or those with heart or lung problems, staging is usually safer.
Key insights
- The same day is one recovery, not an easier one: the first few weeks are harder with no “good leg” to lean on.
- The risk difference is real but small: meta-analyses show higher clot and mortality risk with simultaneous surgery, mostly concentrated in higher-risk patients.
- Fitness decides more than preference: heart, lung and kidney health matter more than how badly you want it over with.
- Staged doesn’t mean years apart: the second knee is often done within a few months.
Before you choose
Don’t make this decision based on cost or leave from work alone. Ask your surgeon how your own heart, lung and blood-clot risk changes the picture. If they’d happily do either, the same day is a reasonable option. If they hesitate, listen to the hesitation.
It’s a common situation. Your X-rays show both knees are worn through, both hurt, and the idea of going through knee replacement twice feels exhausting. So the obvious question comes up in the first consultation: “Can’t you just do both at once?”
Sometimes the answer’s yes. Sometimes it’s “we can, but we shouldn’t”. The difference comes down to your health, your age and how you’d cope with the first few weeks. Here’s how arthroplasty surgery teams actually make that call.
What’s the difference between same-day and staged bilateral knee replacement?
Same-day, or simultaneous, bilateral knee replacement replaces both knees under one anaesthetic in one operation. Staged bilateral replacement replaces one knee, lets you recover, then replaces the other in a second operation weeks or months later. The implants and technique are the same. The difference is timing and total risk.
| Factor | Same day (simultaneous) | Staged (two operations) |
| Anaesthetics | One | Two |
| Hospital stays | One, often a little longer | Two, each usually shorter |
| Total recovery time | One combined recovery | Two recoveries, with a gap |
| Early weeks | Harder, both legs sore | Easier, one good leg |
| Blood loss and transfusion | More in one go | Less each time |
| Clot and mortality risk | Higher in published data | Lower |
| Total cost | Usually lower overall | Usually higher overall |
| Time off work | Usually less overall | Usually more overall |
Same day, two surgeons?
Some centres operate on both knees at once with two teams, others do one knee after the other in the same sitting. Both count as simultaneous. Ask how your surgeon does it.
Is it safe to replace both knees at the same time?
It can be safe for carefully selected, healthy patients, but simultaneous bilateral knee replacement carries higher risks of blood clots, lung clots and death than staged surgery in large studies. The extra risk falls mainly on older patients and those with heart, lung or other serious medical conditions.
What the meta-analyses show
A meta-analysis of 18 studies covering more than 135,000 patients found simultaneous surgery had higher mortality, pulmonary embolism and deep-vein thrombosis but lower deep infection than staged surgery. Revision rates, cardiac and neurological complications didn’t differ significantly.
Mortality numbers, in context
A separate meta-analysis found mortality was significantly higher after simultaneous surgery at 30 days, three months and one year, though in-hospital mortality didn’t differ. The absolute numbers are small for healthy patients, but a relative increase matters if you already carry risk.
Why risk goes up
Two replacements at once mean more blood loss, a longer anaesthetic and a bigger stress response on the body. Fat and marrow from both thigh bones can also enter the bloodstream at the same time, which is one theory for the higher clot risk.
Who’s a good candidate for same-day bilateral knee replacement?
Good candidates are generally younger, fitter patients with no significant heart, lung or kidney disease, a healthy weight, good blood counts and strong motivation for rehab. Both knees should be similarly bad, so that doing one wouldn’t leave the other limiting your recovery.
A rough checklist
- Age: generally younger, often under 70, though fitness matters more than the number.
- Heart and lungs: no significant heart disease, heart failure or lung disease.
- Weight: not severely obese.
- Blood: good haemoglobin before surgery.
- Both knees similarly bad: so one doesn’t hold the other back.
- Support at home: someone to help for the first few weeks.
Who should usually stage
Older patients, people with heart, lung or kidney disease, those with diabetes that isn’t well controlled, or anyone the anaesthetist has concerns about. Staging is also sensible if one knee is clearly worse.
If you stage them, how long should you wait between knees?
Staged bilateral knee replacements are commonly spaced from about six weeks to several months apart, once the first knee has recovered enough to take your weight confidently. Many surgeons prefer to wait until the first knee is comfortable, bending well and strong, rather than following a fixed calendar.
What “ready” looks like
You can walk confidently on the first knee, bend it well, and you’ve recovered from the anaesthetic and blood loss. Your recovery timeline on the first side is the best guide to when the second can happen.
Why not wait years?
The second worn knee often holds back your recovery on the first side. Leaving it too long means limping on it, which can slow the overall result.
Planning around life
Staging lets you plan around work, family events and weather. Many people time the second operation for a quieter period a few months later.
What does recovery look like after both knees are done at once?
After simultaneous bilateral knee replacement, recovery is more demanding in the first two to three weeks because neither leg is a “good leg”. Most patients need a walker and more physio support early, sometimes a short stay in rehab. After that, the two knees recover together, and overall time to full recovery is often similar to one knee.
| Phase | Same day | Staged |
| First week | Hardest, two sore knees | Manageable, one sore knee |
| Weeks 2 to 6 | Building up both at once | First knee recovering |
| Months 2 to 3 | Both improving together | Second operation, then repeat |
| Overall | One combined recovery | Two shorter recoveries plus a gap |
Pain relief
You’ll have pain from two knees at once, so good pain control is essential to keep physio on track.
Physio is non-negotiable
Bending both knees early prevents stiffness. Missing physio after a bilateral replacement is how people end up with two stiff knees instead of one.
Does robotic surgery or insurance change the decision?
Robotic-assisted knee replacement can improve implant positioning, but it doesn’t remove the medical risks of operating on two knees at once, so it doesn’t change who should stage. Insurance coverage depends on your policy, and some insurers have specific rules on bilateral surgery, so check before you decide.
Robotics
Robotic systems help with precision in knee replacement surgery. They don’t change your heart or lung risk, which is what drives the same day vs staged decision.
Insurance
Check whether your policy covers both knees in one admission, has sub-limits per joint or requires pre-authorisation for each. Our cashless insurance and TPA list is a good starting point.
Both hips?
The same logic applies to hips, with its own pros and cons. We’ve covered it in our guide to bilateral hip replacement.
Wrapping up
If both knees need replacing, there’s no single right answer. Same-day surgery gets it over in one go with one recovery and usually lower total cost, but carries more risk, especially for older or less healthy patients. Staged surgery is two operations and two recoveries, but it’s the safer route for many people. Your health, not your impatience, should decide.
At Kaushalya Hospital, a 150-bed trust hospital in Thane West with intensive care on site, the orthopaedic team performs both simultaneous and staged knee replacement and works with the anaesthetists to assess heart, lung and clot risk before recommending either. If both your knees are wearing out, book an arthroplasty consultation and get a plan built around your own health.
FAQs
Can both knees be replaced at the same time?
Yes, it’s called simultaneous bilateral knee replacement. It suits younger, healthy patients best. Older patients or those with heart, lung or kidney problems are usually advised to have the knees done separately.
Is it better to have both knees replaced at once?
It depends on your health. Same-day surgery means one recovery and often lower cost, but large studies show higher risks of clots and death. Staged surgery is generally safer for higher-risk patients.
How long should you wait between knee replacements?
Commonly six weeks to several months, once the first knee is comfortable, bending well and strong enough to take your weight confidently. Your surgeon will judge readiness rather than follow a fixed calendar.
Is recovery harder after bilateral knee replacement?
Yes, in the first two to three weeks, because neither leg is a “good leg”. You’ll need more physio support and a walker early. After that, both knees usually recover together.
What are the risks of simultaneous bilateral knee replacement?
Compared with staged surgery, the main risks are higher rates of blood clots, lung clots and death in published studies, plus more blood loss. Deep infection was actually lower in one large meta-analysis.
Does insurance cover both knees at once?
Often, but it depends on your policy. Some policies have per-joint sub-limits or specific bilateral rules. Check coverage and pre-authorisation requirements with your insurer or TPA before surgery.
