Knee Replacement Surgery

What is knee replacement surgery?

The two main types of knee replacement are:

  • Total knee replacement (TKR) – involves replacing the end of the thigh bone (femur) and the top of the shin bone (tibia).
  • Partial knee replacement (PKR) – half or part of the knee is replaced, usually the inside of the knee.

How common is knee replacement surgery?

  • This is a very common procedure – over 100,000 people have this procedure each year in the UK. The average age of people getting a knee replacement is 69 years (1).

Should I worry?

  • No.
  • Most knee replacements reduce pain and restore function. 80% of total knee replacements last for 25 years (4).

Who is most likely to suffer from knee replacement surgery?

Commonly associated conditions:

  • Osteoarthritis (OA) is the reason for replacements in 99% of cases; 56% of these are women (2).

Other causes include:

  • Rheumatoid arthritis or other similar inflammatory arthritis.
  • Severe trauma to the knee bones.
  • Bone death due to abrupt loss of blood supply to them.
  • Gout.
  • Haemophilia.
  • Deformed knee.

What are the common symptoms?

Post-surgery symptoms include:

  • Pain, swelling and stiffness in and around the knee.
  • Stiffness in the knee – meaning walking and driving can be difficult after your surgery.

What can I do?


  • Physiotherapy – the stronger the muscles are before surgery should improve the outcome of the replacement.


  • Medications – to relieve symptoms post-surgery.
  • Ice packs for knee and elevation of affected leg helps with pain and swelling.
  • Use of walking aids to help with mobility issues.
  • Physiotherapy to restore range of motion, reduce pain and swelling, and return strength to your muscles.

How long will it take to recover?

  • Usually in hospital for 3-5 days post-surgery, although recovery times can vary.
  • Most people stop using walking aids after 6 weeks.
  • You can start driving after 6-8 weeks.
  • Full recovery can take up to 2 years – a small minority will experience pain after 2 years.

1. Introduction

Knee replacement is a common operation that an orthopaedic surgeon will perform to replace the worn or damaged knee surfaces with an artificial joint. Both partial knee replacements (PKR) and total knee replacements (TKR) are common and vary based on individual considerations. The most common reason for undergoing a knee replacement is osteoarthritis (OA). OA is a common and potentially debilitating condition. In the end stages of OA, knee replacements are the mainstay of treatment and are effective in many cases (1). The aim of knee replacement surgery is the long-term relief of pain and restoring function.

Usually, your GP or physiotherapist will consider sending you for an orthopaedic examination if you have already exhausted other non-operative pathways. This includes extensive physiotherapy, painkillers, walking aids and injections. A clinician will also consider the nature of your pain and function before making the decision to refer you to an orthopaedic surgeon. They will make this decision in light of whether the pain is affecting your quality of life, mental wellbeing and sleep.


2. Signs & Symptoms

After surgery, common symptoms include pain, stiffness and inflammation. Usually, you will be in hospital for 3 to 5 days but recovery times can vary. Once you are able to be discharged from hospital you will be given advice about looking after your knee at home. Walking can be difficult so you will need to use a frame or crutches at first and a physiotherapist will teach you exercises to help strengthen your knee.

Most people can stop using walking aids around 6 weeks after surgery and start driving after 6 to 8 weeks. Full recovery can take up to 2 years as scar tissue heals and your muscles are restored by exercise. An exceedingly small amount of people will continue to have some pain after 2 years.

3. Causes

It is reported that 99% of knee replacements are due to osteoarthritis. Other less common conditions include rheumatoid arthritis or other similar inflammatory arthritis, severe trauma to the knee bones, bone death due to abrupt loss of blood supply to them, gout, haemophilia and knee deformation (2).


4. Risk Factors

This is not an exhaustive list. These factors could increase the likelihood of someone needing a total knee replacement. It does not mean everyone with these risk factors will have a knee replacement.

Other causes include:

Knee replacement surgery is common and most people do not have complications. However, as with any operation, there are risks as well as benefits.
Complications are rare but can include:

In some cases, the new knee joint may not be completely stable and further surgery may be needed to correct it. Another risk of knee replacement surgery is the failure of the artificial joint. Daily use wears on even the strongest metal and plastic parts. Joint failure risk is higher if you stress the joint with high-impact activities or excessive weight-bearing. The most common indications for revision include aseptic loosening, infection and pain (6).

You must inform your doctor immediately if you notice:

An infected knee replacement usually requires antibiotics to kill the bacteria and/or surgery to remove the artificial parts. After the infection is cleared, another surgery is performed to install a new knee.


5. Prevalence

In 2017, there were 106,334 knee replacement procedures carried out in England, Wales and Northern Ireland. The average age of patients undergoing this surgery was 69 years (4). The incidence between gender is evenly split but is slightly higher in women at 56% (2).

6. Assessment & Diagnosis

Musculoskeletal physiotherapists and other appropriately qualified healthcare professionals can provide you with a diagnosis by obtaining a detailed history of your symptoms. A series of physical tests might be performed as part of your assessment to rule out other potentially involved structures and gain a greater understanding of your physical abilities to help facilitate an accurate working diagnosis.

Your treating clinician will want to know how your condition affects you day-to-day so that treatment can be tailored to your needs and personalised goals can be established. Intermittent reassessment will ascertain if you are making progress towards your goals and will allow appropriate adjustments to your treatment to be made. Imaging studies like MRI or ultrasound scans are usually not required to achieve a working diagnosis but in unusual presentations, they may be warranted.

A knee replacement will be considered based on the individual circumstances of each person. It is a major surgery so it is normally only recommended if other treatments, such as physiotherapy or steroid injections, have not reduced pain or improved mobility.

You may be offered knee replacement surgery if:

  • You have severe pain, swelling and stiffness in your knee joint and your mobility is reduced.
  • Your knee pain is so severe that it interferes with your quality of life and sleep.
  • Everyday tasks, such as shopping or getting out of the bath, are difficult or impossible.
  • You are feeling depressed because of the pain and lack of mobility.
  • You cannot work or have a social life.
  • You have exhausted all other treatment options.

You will also need to be well enough to cope with both a major operation and the rehabilitation afterwards.

7. Self-Management

Before your knee replacement takes place, you will undergo pre-operative physiotherapy. Exercise promoting strength and flexibility of the knee can improve the outcome of the replacement. In a review of the literature, it was found that patients undergoing knee replacements had significant improvements in function, quadriceps strength and length of hospital stay (5).

Most people return home within 3-5 days. Upon returning home, you may feel extremely tired at first and the tissues surrounding your new knee will take time to heal. Follow the advice of the surgical team and call your GP if you have any worries or queries. You may be eligible for up to 6 weeks of home help and there may be aids that can help you. You may also want to arrange for someone to help you for a week or so.

Post-operative wound healing is critical to the outcome of a knee replacement. Therefore, it is vital to keep the wound clean and dry during this time. Each surgeon will have different protocols in managing wounds, so it is important to find out the surgeon’s specific wound care protocols.

The exercises your musculoskeletal physiotherapist gives you are an important part of your recovery. It is essential you continue with them once you are at home. Your rehabilitation will be monitored by a physiotherapist. Most people can manage without walking aids after 6 weeks (about 1½ months) but it is important that you adhere to the prescribed home exercises during this time. Most hospitals will give you an advice leaflet which contains all home exercises. You may also be referred to an outpatient department to see a physiotherapist where they will progress walking and other exercises. You can start driving after 6-8 weeks. Full recovery can take up to 2 years and a small number of people experience pain after 2 years.


8. Rehabilitation

After surgery, you will be under the care of a multidisciplinary team at the hospital which consists of your surgeon, ward nurse (who deals with the pain management side), musculoskeletal physiotherapist (deals with the progression of your mobility and exercises) and occupational therapist (they help you by assessing your home environment and may help you have some assistive aids to help with daily activities).

During your stay in the hospital, a physiotherapist will teach you exercises to help with symptoms and to start to strengthen your knee. You can usually begin these the day after your operation. It is important to follow the physiotherapist’s advice to avoid complications or dislocation of your new joint. You will also be provided with walking aids to help with mobility for the first 6 weeks.

It is normal to have initial discomfort while walking and exercising, and your legs and feet may be swollen. You may be put on a passive motion machine to restore movement in your knee and leg. This support will slowly move your knee while you are in bed. It helps to decrease swelling by keeping your leg raised and helps improve your circulation.

After being discharged from the hospital, you will be provided with an exercise programme to improve the mobility, strength and flexibility of the knee. Here are three rehabilitation programmes created by our specialist physiotherapists for recovery post-knee replacement. In some instances, a one-to-one assessment is appropriate to individually tailor targeted rehabilitation. However, these programmes provide an excellent starting point as well as clearly highlighting exercise progression.

9. Knee Replacement Surgery Rehabilitation Plans

Early Plan

The early plan is designed to provide you with some exercises to help increase movement and begin the process of getting the thigh muscles to re-engage. Pain should not exceed 3/10 on your self-perceived pain scale whilst completing this exercise programme.

Early Plan - Rating

Intermediate Plan

Here our focus becomes regaining strength in the hips and legs. It is expected that you would be carrying on some of the movement-based exercises from the early programme and add in these exercises. Pain should not exceed 4/10 on your self-perceived pain scale whilst completing this exercise programme.

Intermediate Plan - Rating

Advanced Plan

In this plan, the exercises increase in difficulty as well as becoming more functional (whole-body) movements. Pain should not be any greater, but we would expect some increase in fatigue when performing these exercises Pain should not exceed 4/10 on your self-perceived pain scale whilst completing this exercise programme.

Advanced Plan - Rating

10. Return to Sport/Normal Life

For patients wanting to return to physically demanding activities or sport, we would encourage a consultation with a physiotherapist as you will require further progression beyond the advanced rehabilitation stage. There is no restriction once you recover from your knee replacement, which can take up to 2 years. Many people do not feel comfortable kneeling for more than brief periods but any form of sport that does not cause significant pain or swelling is permitted.

As part of a multi-modal treatment approach, your musculoskeletal physiotherapist may also use a variety of other pain-relieving treatments to support symptom relief and recovery. Whilst recovering you might benefit from a further assessment to ensure you are making progress and establish the appropriate progression of treatment. Ongoing support and advice will allow you to self-manage and prevent future reoccurrence.

11. Other Treatment Options

A knee replacement is only considered if all other treatment options are exhausted. These treatments include:

  • Intensive physiotherapy programme.
  • Lifestyle changes – including weight loss and smoking cessation.
  • Steroid injections.

There are other types of surgery which are an alternative to knee replacement but results are often not as good in the long term. Your doctor will discuss the best treatment option with you. Other types of surgery may include:

  • Arthroscopic washout and debridement – a tiny telescope (arthroscope) is inserted into the knee, which is then washed out with saline to clear any bits of bone or cartilage.
  • Osteotomy – the surgeon cuts the shin bone and realigns it so that your weight is no longer carried by the damaged part of the knee.
  • Mosaicplasty – a keyhole operation that involves transferring plugs of hard cartilage, together with some underlying bone from another part of your knee, to repair the damaged surface.

12. Links for Further Reading
Arthritis Research UK information booklet – click here.


  1. Carr AJ, Robertsson O, Graves S et al. (2012). Knee replacement. Lancet. 2012; 379: 1331-1340.
  2. Kassam AM, Dieppe P, Toms AD. (2012).An analysis of time and money spent on investigating painful total knee replacements. Br J Med Pract. 2012; 5: a526.
  3. Rooks, D.S., Huang, J.I.E., Bierbaum, B.E., Bolus, S.A., Rubano, J., Connolly, C.E., Alpert, S., Iversen, M.D. and Katz, J.N., (2006). Effect of preoperative exercise on measures of functional status in men and women undergoing total hip and knee arthroplasty. Arthritis Care & Research: Official Journal of the American College of Rheumatology, 55(5), pp.700-708.
  4. Evans JT, Walker R, Evans W et al. How long does a knee replacement last? A systematic review and meta-analysis of case series and national registry reports with more than 15 years of follow-up. Lancet. 2019;393:655-63.
  5. Moyer, Rebecca PT, PhD1,a; Ikert, Kathy PT2; Long, Kristin PT3; Marsh, Jacquelyn PhD4 The Value of Preoperative Exercise and Education for Patients Undergoing Total Hip and Knee Arthroplasty, JBJS Reviews: (2017) – Volume 5 – Issue 12 – p e2 doi: 10.2106/JBJS.RVW.17.00015.
  6. Khan M, Osman K, Green G, Haddad FS. The epidemiology of failure in total knee arthroplasty: avoiding your next revision. Bone Joint J. (2016 Jan);98-B(1 Suppl A):105-12. doi: 10.1302/0301-620X.98B1.36293. PMID: 26733654.
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Structural knee injury, triggered either by a tear or through wear and tear.

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Degenerative Meniscus

Seen to be normal as we age, but in some situations can result in knee aches, pain or joint swelling.

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Patellar Tendinopathy

Knee pain at the lower border of the kneecap which is also known as ‘jumper’s knee’.

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Fat Pad Impingement

A rare condition affecting the adipose (fat) tissue that sits under the kneecap (patella) between the joint spaces of the knee.

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