Knee replacement surgery
(partial and total)

Deciding whether to have knee surgery can feel overwhelming. This guide will help you understand your knee surgery options, benefits, risks, and recovery so you can make an informed decision about the right treatment for your condition.

Knee replacement (also called knee arthroplasty), is a commonly performed operation to treat established arthritis of the knee (link to knee arthritis). It replaces the worn out bearing surfaces of the knee with metal and plastic, to improve pain and restore function.
The knee joint comprises three smaller joints (or ‘compartments’) - the medial compartment on the inner side of the knee, the lateral compartment on the outer side, and the patellofemoral (kneecap) joint on the front. When all three parts of the knee are damaged with arthritis, all three parts are replaced using a total (full) knee replacement. If only one of three compartments is arthritic, then it does not make sense to replace the whole knee, as most of it is still normal and healthy. In this situation, only the arthritic part is replaced, leaving the rest of the healthy knee alone. This is a partial (or unicompartmental) knee replacement.
Studies show that a partial joint replacement will feel more like your normal knee and function better than a total knee replacement. However, because some of the cartilage remains there is a chance of developing arthritis in that later, and subsequently needing further surgery.

A total knee replacement may feel more ‘mechanical’ than your normal knee, but will have less chance of requiring further surgery in the future.

In summary, both are good procedures, and are performed for different patterns of arthritis.
Knee replacements comprise metal implants that are fixed to the bone with cement, and plastic inserts to form the new knee bearing surface. The commonly used metals contain cobalt, chromium, titanium and some nickel. The plastic is a high density polyethylene. For patients with nickel allergy, ceramic alternatives are available.
The metal plates are made of titanium, which, although not magnetic, may trigger walk-through metal detectors, especially in more sensitive security systems.

Newer scanners (millimetre wave or body scanners) often detect the implant visually instead of relying solely on metal detection, so alarms may be less common than in the past.
Although routinely performed, knee replacement is major surgery, and is associated with real risks of having a complication. Every effort must therefore be made to exhaust all non-operative treatments prior to considering a replacement procedure. These can be found here.
The surgery will be explained to you by Mr Smith in clinic, the alternatives, likely recovery period and any associated risks discussed. You will have a pre-operative clinic appointment to ensure that you are safe for surgery, and that there is no aspect of your health that can be optimised prior to having surgery. You will be informed at this stage when to stop any regular medications, and what time you can eat and drink until prior to the surgery.

On the day of surgery you will see Mr Smith and the anaesthetist prior to the surgery, to ensure that all questions have been addressed. The consent form will be checked with you, and the correct leg marked. You will often see a physiotherapist prior to your surgery also.
Prior to the surgery, Mr Smith will plan the position and alignment of your knee replacement from your x-rays, to ensure that it best matches your anatomy.

The procedure is usually performed under a general anaesthetic (fully asleep), with a nerve block in the thigh for pain relief.

You will be given antibiotics into the vein at the time of surgery to reduce the risk of infection.

An incision is made on the front of the knee from the bump at the top of the shin bone (tibial tuberosity) to just above the kneecap (patella). The patella is moved to the side to allow access to the knee joint.

Using jigs to achieve the correct angles, the ends of the tibia and femur are cut and shaped to accept the metal implants. This is where the arthritis is removed. The ligaments, tendons, nerves and blood vessels are protected throughout the surgery.

Trial implants of the correct size for your knee are inserted, and the ligament tension and the movement within the replacement are then checked carefully too ensure it functions as well as possible. Any changes can be made at this point.

The definitive impacts are subsequently cemented onto the prepared bone for stability.

The incisions are then washed with sterile water, and closed with stitch that absorbs. Adherent dressings are applied, with a bandage over the top.
The replacement surgery itself takes approximately an hour, but there is additional time required for the anaesthetic and recovery. One can expect to be away from the ward for 2 - 3 hours.
Most patients will go home the day after surgery, but some take a little longer, This allows for good pain relief for the night following the surgery, and the opportunity to work with the physiotherapists to ensure that you are safe and confident on your feet prior to leaving hospital. If you have stairs at home, then your ability to use these will be assessed prior to discharge.
Having a knee replacement can be tough, and people experience it very differently. Some will be walking unaided faster than others, and some will experience more pain than others. This is normal, and everyone recovers in their own time. Even if you have had a previous replacement on the other knee, your subsequent replacement may be different.

The first few days can be a uncomfortable, but you will be discharged with appropriate pain relief. I suggest that you take this regularly for a week following the operation, then start weaning it down. It is best to be comfortable and able to do your early rehabilitation rather than playing ‘catch up’ with pain relief. Regular icing of the knee will help to bring dow the swelling, and this may need to continue for weeks.

The quadriceps muscles often go to sleep after the surgery, and the key to the early recovery is getting them contracting again. This will allow you to start weaning off crutches, and returning towards walking unaided. The knee will be swollen, and can remain so for a up to a year. This is normal.

You will be seen for a wound check at two weeks, and a follow-up clinic appointment will be arranged for 6-8 weeks following the surgery. Most people start to really turn the corner in terms of pain relief and function at this point, and are subsequently doing well by approximately 3 months. Improvement in the knee function however will continue gradually all the way until 12 months.

The key to successful recovery is engagement in the post-operative physiotherapy programme. This is a structured, evidence-based rehabilitation regimen that ensures that the muscles and knee control are restored after surgery, to allow you to ultimately return to activities of your choosing. This must be guided by a qualified physiotherapist. An outline of the rehabilitation timeline and goals can be found here.
Regards returning to work or studies, I advise to return when ‘no longer distracted by either the pain or pain killers’. If you have an office or home based job, this can be as early as one or two weeks. For more physically demanding jobs, return to work can take longer, but you can be provided with an appropriate fitness to work (sick) note for the period.

With regards to returning to activities, this will be dictated by how the knee is recovering with physio. Cycling and swimming are good rehabilitative activities are can be commenced from as early as 4 - 6 weeks. Low impact activities (golf, padel, doubles tennis) will realistically be resumed after approximately 3-4 months. Driving can normally be resumed by approximately 4 weeks. I advise you inform your car insurer prior to doing so.

What are the potential risks?

Knee replacement surgery is generally safe and effective, but it is still a major operation, and as such it carries certain risks.Every effort will be made to minimise these risks, but to allow this it is important that you mention any health issues at the pre-operative assessment. Below is a breakdown of the risks by frequency and approximate percentages, based on medical literature and clinical studies. Mr Smith will speak to you in detail about these prior to any surgery.

Risk	Partial Knee Replacement	Total Knee Replacement	Comments
Pain and stiffness	5–10%	5–10%	Stiffness and discomfort can occur in both; may be more pronounced in total knee replacement
Swelling	5–10%	5–10%	Common in both types; typically resolves with time
Wound infection (superficial)	1–5%	1–5%	Similar risk; managed with oral antibiotics
Numbness	5–10%	5–10%	Due to superficial nerve irritation; slightly more common in total knee
Blood loss requiring transfusion	0.5–1%	1–5%	More common in total due to larger surgical area
Blood clot (Deep vein thrombosis/Pulmonary embolus/heart attack/stroke)	0.5–1%	0.5–1%	Risk present in both; You will be prescribed a blood thinner after the surgery to reduce this risk
Deep joint infection	0.1–0.5%	0.1–1%	Higher risk in total knee; may require washout or revision
Instability or dislocation	0.1–0.5%	0.5–1%	More common in total knee, especially with soft tissue imbalance
Fracture during surgery	0.1%	0.5–1%	More likely in total due to greater bone preparation
Persistent pain	0.5–1%	0.5–1%	May occur in both despite technically successful surgery
Need for further surgery	0.5–1%	1–5%	Total knee has higher long-term revision rate than partial
Nerve or vessel injury	<0.1%	<0.1%	Extremely rare in both; more likely in complex total knees
Complex Regional Pain Syndrome (CRPS)	<0.1%	<0.1%	Chronic pain syndrome can occur after any surgery
Anaesthetic complication	<0.1%	<0.1%	Serious allergic or cardiorespiratory reaction to anaesthetic
Patellar tendon injury	<0.1%	0.1%	More likely in total knee replacement if patella is resurfaced
Life threatening or altering complication	<0.1%	<0.1%
Prosthesis wear or loosening	1–2% per year	0.5–1% per year	Partial knees often last 10–15 years; totals may last 15–20+ years
Revision surgery	10–20% at 15 years	5–10% at 15 years	Total knee has higher survivorship in the long term
Progression of arthritis	10–20%	Not applicable	Affects other compartments in partial knees; not an issue in totals
Kneeling discomfort	10–20%	20–40%	More common in total knee due to anterior incision and patellar work
Residual functional limitation	10–20%	10–30%	More likely in total; partial knees retain more natural function

Based on long-term evidence and registry data, 80–90% of patients are satisfied with the outcome of their replacement at one year. That means that up to 10–20% may have some ongoing pain, stiffness, or “not quite right” feeling, even if the implant looks fine on X-ray.

Pain relief: 90-95% of patients report major improvement in pain, especially night pain and pain on activity. The knee may not feel “completely natural”, and many describe it as a “mechanical” feeling, even though pain is gone.

Function and mobility: Walking, climbing stairs and standing are much easier. Return to low impact activities like golf, swimming, cycling, hiking and tennis are realistic. Most patients will achieve a bend of 110–120°.

Longevity of the implant: Modern total knee implants last a long time. 98% are still working well after 15 years, and will likely last well beyond 20 years with good function. The partial joint replacement used by Mr Smith is relatively new, but but 98% are functioning well at 5 years. Older implants with similar design have shown 92% lasting well beyond 15 years.
Please contact the hospital where your surgery was performed, and they will easily be able to get in contact with Mr Smith on your behalf.

Knee replacement (also called knee arthroplasty), is a commonly performed operation to treat established arthritis of the knee (link to knee arthritis). It replaces the worn out bearing surfaces of the knee with metal and plastic, to improve pain and restore function.
The knee joint comprises three smaller joints (or ‘compartments’) - the medial compartment on the inner side of the knee, the lateral compartment on the outer side, and the patellofemoral (kneecap) joint on the front. When all three parts of the knee are damaged with arthritis, all three parts are replaced using a total (full) knee replacement. If only one of three compartments is arthritic, then it does not make sense to replace the whole knee, as most of it is still normal and healthy. In this situation, only the arthritic part is replaced, leaving the rest of the healthy knee alone. This is a partial (or unicompartmental) knee replacement.
Studies show that a partial joint replacement will feel more like your normal knee and function better than a total knee replacement. However, because some of the cartilage remains there is a chance of developing arthritis in that later, and subsequently needing further surgery.

A total knee replacement may feel more ‘mechanical’ than your normal knee, but will have less chance of requiring further surgery in the future.

In summary, both are good procedures, and are performed for different patterns of arthritis.
Knee replacements comprise metal implants that are fixed to the bone with cement, and plastic inserts to form the new knee bearing surface. The commonly used metals contain cobalt, chromium, titanium and some nickel. The plastic is a high density polyethylene. For patients with nickel allergy, ceramic alternatives are available.
The metal plates are made of titanium, which, although not magnetic, may trigger walk-through metal detectors, especially in more sensitive security systems.

Newer scanners (millimetre wave or body scanners) often detect the implant visually instead of relying solely on metal detection, so alarms may be less common than in the past.
Although routinely performed, knee replacement is major surgery, and is associated with real risks of having a complication. Every effort must therefore be made to exhaust all non-operative treatments prior to considering a replacement procedure. These can be found here.
The surgery will be explained to you by Mr Smith in clinic, the alternatives, likely recovery period and any associated risks discussed. You will have a pre-operative clinic appointment to ensure that you are safe for surgery, and that there is no aspect of your health that can be optimised prior to having surgery. You will be informed at this stage when to stop any regular medications, and what time you can eat and drink until prior to the surgery.

On the day of surgery you will see Mr Smith and the anaesthetist prior to the surgery, to ensure that all questions have been addressed. The consent form will be checked with you, and the correct leg marked. You will often see a physiotherapist prior to your surgery also.
Prior to the surgery, Mr Smith will plan the position and alignment of your knee replacement from your x-rays, to ensure that it best matches your anatomy.

The procedure is usually performed under a general anaesthetic (fully asleep), with a nerve block in the thigh for pain relief.

You will be given antibiotics into the vein at the time of surgery to reduce the risk of infection.

An incision is made on the front of the knee from the bump at the top of the shin bone (tibial tuberosity) to just above the kneecap (patella). The patella is moved to the side to allow access to the knee joint.

Using jigs to achieve the correct angles, the ends of the tibia and femur are cut and shaped to accept the metal implants. This is where the arthritis is removed. The ligaments, tendons, nerves and blood vessels are protected throughout the surgery.

Trial implants of the correct size for your knee are inserted, and the ligament tension and the movement within the replacement are then checked carefully too ensure it functions as well as possible. Any changes can be made at this point.

The definitive impacts are subsequently cemented onto the prepared bone for stability.

The incisions are then washed with sterile water, and closed with stitch that absorbs. Adherent dressings are applied, with a bandage over the top.
The replacement surgery itself takes approximately an hour, but there is additional time required for the anaesthetic and recovery. One can expect to be away from the ward for 2 - 3 hours.
Most patients will go home the day after surgery, but some take a little longer, This allows for good pain relief for the night following the surgery, and the opportunity to work with the physiotherapists to ensure that you are safe and confident on your feet prior to leaving hospital. If you have stairs at home, then your ability to use these will be assessed prior to discharge.
Having a knee replacement can be tough, and people experience it very differently. Some will be walking unaided faster than others, and some will experience more pain than others. This is normal, and everyone recovers in their own time. Even if you have had a previous replacement on the other knee, your subsequent replacement may be different.

The first few days can be a uncomfortable, but you will be discharged with appropriate pain relief. I suggest that you take this regularly for a week following the operation, then start weaning it down. It is best to be comfortable and able to do your early rehabilitation rather than playing ‘catch up’ with pain relief. Regular icing of the knee will help to bring dow the swelling, and this may need to continue for weeks.

The quadriceps muscles often go to sleep after the surgery, and the key to the early recovery is getting them contracting again. This will allow you to start weaning off crutches, and returning towards walking unaided. The knee will be swollen, and can remain so for a up to a year. This is normal.

You will be seen for a wound check at two weeks, and a follow-up clinic appointment will be arranged for 6-8 weeks following the surgery. Most people start to really turn the corner in terms of pain relief and function at this point, and are subsequently doing well by approximately 3 months. Improvement in the knee function however will continue gradually all the way until 12 months.

The key to successful recovery is engagement in the post-operative physiotherapy programme. This is a structured, evidence-based rehabilitation regimen that ensures that the muscles and knee control are restored after surgery, to allow you to ultimately return to activities of your choosing. This must be guided by a qualified physiotherapist. An outline of the rehabilitation timeline and goals can be found here.
Regards returning to work or studies, I advise to return when ‘no longer distracted by either the pain or pain killers’. If you have an office or home based job, this can be as early as one or two weeks. For more physically demanding jobs, return to work can take longer, but you can be provided with an appropriate fitness to work (sick) note for the period.

With regards to returning to activities, this will be dictated by how the knee is recovering with physio. Cycling and swimming are good rehabilitative activities are can be commenced from as early as 4 - 6 weeks. Low impact activities (golf, padel, doubles tennis) will realistically be resumed after approximately 3-4 months. Driving can normally be resumed by approximately 4 weeks. I advise you inform your car insurer prior to doing so.

What are the potential risks?

Risk	Partial Knee Replacement	Total Knee Replacement	Comments
Pain and stiffness	5–10%	5–10%	Stiffness and discomfort can occur in both; may be more pronounced in total knee replacement
Swelling	5–10%	5–10%	Common in both types; typically resolves with time
Wound infection (superficial)	1–5%	1–5%	Similar risk; managed with oral antibiotics
Numbness	5–10%	5–10%	Due to superficial nerve irritation; slightly more common in total knee
Blood loss requiring transfusion	0.5–1%	1–5%	More common in total due to larger surgical area
Blood clot (Deep vein thrombosis/Pulmonary embolus/heart attack/stroke)	0.5–1%	0.5–1%	Risk present in both; You will be prescribed a blood thinner after the surgery to reduce this risk
Deep joint infection	0.1–0.5%	0.1–1%	Higher risk in total knee; may require washout or revision
Instability or dislocation	0.1–0.5%	0.5–1%	More common in total knee, especially with soft tissue imbalance
Fracture during surgery	0.1%	0.5–1%	More likely in total due to greater bone preparation
Persistent pain	0.5–1%	0.5–1%	May occur in both despite technically successful surgery
Need for further surgery	0.5–1%	1–5%	Total knee has higher long-term revision rate than partial
Nerve or vessel injury	<0.1%	<0.1%	Extremely rare in both; more likely in complex total knees
Complex Regional Pain Syndrome (CRPS)	<0.1%	<0.1%	Chronic pain syndrome can occur after any surgery
Anaesthetic complication	<0.1%	<0.1%	Serious allergic or cardiorespiratory reaction to anaesthetic
Patellar tendon injury	<0.1%	0.1%	More likely in total knee replacement if patella is resurfaced
Life threatening or altering complication	<0.1%	<0.1%
Prosthesis wear or loosening	1–2% per year	0.5–1% per year	Partial knees often last 10–15 years; totals may last 15–20+ years
Revision surgery	10–20% at 15 years	5–10% at 15 years	Total knee has higher survivorship in the long term
Progression of arthritis	10–20%	Not applicable	Affects other compartments in partial knees; not an issue in totals
Kneeling discomfort	10–20%	20–40%	More common in total knee due to anterior incision and patellar work
Residual functional limitation	10–20%	10–30%	More likely in total; partial knees retain more natural function

Based on long-term evidence and registry data, 80–90% of patients are satisfied with the outcome of their replacement at one year. That means that up to 10–20% may have some ongoing pain, stiffness, or “not quite right” feeling, even if the implant looks fine on X-ray.

Pain relief: 90-95% of patients report major improvement in pain, especially night pain and pain on activity. The knee may not feel “completely natural”, and many describe it as a “mechanical” feeling, even though pain is gone.

Function and mobility: Walking, climbing stairs and standing are much easier. Return to low impact activities like golf, swimming, cycling, hiking and tennis are realistic. Most patients will achieve a bend of 110–120°.

Longevity of the implant: Modern total knee implants last a long time. 98% are still working well after 15 years, and will likely last well beyond 20 years with good function. The partial joint replacement used by Mr Smith is relatively new, but but 98% are functioning well at 5 years. Older implants with similar design have shown 92% lasting well beyond 15 years.
Please contact the hospital where your surgery was performed, and they will easily be able to get in contact with Mr Smith on your behalf.

Knee replacement surgery
(partial and total)

Deciding whether to have knee surgery can feel overwhelming. This guide will help you understand your knee surgery options, benefits, risks, and recovery so you can make an informed decision about the right treatment for your condition.

Book a consultation

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Knee replacement surgery (partial and total)

Deciding whether to have knee surgery can feel overwhelming. This guide will help you understand your knee surgery options, benefits, risks, and recovery so you can make an informed decision about the right treatment for your condition.

Knee replacement surgery
(partial and total)