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Knee replacement

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What it is?

Knee replacement is the surgery done to replace the affected parts of the knee joint with a manmade implant. The affected generally degenerated joint surface of the bones of thigh and leg (femur, tibia, and patella) which form the knee joint are replaced along with the adjacent bone by an implant with a structure similar to natural knee joint.

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Who are the candidates for knee replacement?

The patients of arthritis who don’t get significant relief in pain or improvement of knee function after using the medical treatment and lifestyle modifications (weight loss, exercise, physiotherapy, etc ) are considered as a candidate for knee replacement.

It is important to try non-surgical options first because knee replacement can also wear out with time and can have complications as seen in other surgeries.


Age limit is not an absolute criterion, rather the severity of symptoms is the most important criterion to decide a candidate for knee replacement. Most replacements are done in the age group of 50-80 years.

Knee replacement can also be required in young patients however it is rarely needed as only a few young people suffer from severe knee problems that require replacement. Knee replacement can be done in young patients who develop severe knee problems because of hemophilia, juvenile idiopathic arthritis, post-traumatic arthritis, and skeletal dysplasia.

How long does the knee replacement last?

It generally lasts for 10-20 years on average. However, with improvement in the implant quality and surgical techniques, it is considered that 85% of knee implants last longer than 20 years.

What is the aim of knee replacement?

To relieve pain, improve knee function, and improve quality of life,.

How common it is?

According to Frost and Sullivan research approx. 70,000 joint replacement surgeries were done in 2011 which has been expected to grow at a rate of 26.7% during 2010-17 in India. Whereas, in the US, approximately 700,000 knee replacement procedures are performed each year.

What is the success rate of knee replacement?

According to AAOS, more than 90% of people after replacement experience a remarkable improvement in their symptoms. They experience significantly less pain and considerable improvement in the ability to perform common daily activities.

National TKA registry reported the post total knee replacement survival rates of approx. 95% at 10 years and just below 90% at 20 years for patients of osteoarthritis.

What are the tests/examinations done to assess the condition of the knee?

An evaluation with an orthopedic surgeon consists of several components:

• A medical history. Your orthopedic surgeon will gather information about your general health and ask you about the extent of your knee pain and your ability to function.

• A physical examination. This will assess knee motion, stability, strength, and overall leg alignment.

• X-rays. These images help to determine the extent of damage and deformity in your knee.

• Other tests. Occasionally blood tests, or advanced imaging such as a magnetic resonance imaging (MRI) scan, may be needed to determine the condition of the bone and soft tissues of your knee.

Your orthopedic surgeon will review the results of your evaluation with you and discuss whether total knee replacement is the best method to relieve your pain and improve your function. Other treatment options — including medications, injections, physical therapy, or other types of surgery — will also be considered and discussed.

In addition, your orthopedic surgeon will explain the potential risks and complications of total knee replacement, including those related to the surgery itself and those that can occur over time after your surgery.

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What are the tests/examination needed to be done to consider you fit for undergoing knee replacement? 

Physical examination:

It is done to assess the physical condition of the body to assure sustenance during surgery and proper recovery after it. People with chronic conditions like heart disease, diabetes, etc may also be assessed by a specialist.

Laboratory tests:

Blood tests- haemogram, TLC, DLC, PT, INR

Urine routine


Urinary Evaluations: indicated in persons with a recent or frequent history of UTI. Older persons with urinary complaints should also be evaluated and managed accordingly for any problem related to the prostate.

Dental Evaluation: is done to assess for any source of infection which is then managed accordingly.

Medications: It is important to inform your doctor about the medicines that you are taking and discuss with him which one to stop or continue.

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How knee replacement surgery is done?


Knee replacement is done in OT after giving anesthesia. The aim of the anesthesia is to enable a person to go through the surgery without feeling pain or any discomfort.

When anesthesia is given to make you lose consciousness, it is called General anesthesia. Whereas, when the anesthesia is given into the spine it causes loss of sensation below the waist called as called Spinal/epidural anesthesia. Sometimes, anesthesia is also given in a nerve receiving sensation from the knee called a Nerve block.

The type of anesthesia used will be decided by the doctor according to the general condition of the person also considering his/her preference too.


The doctor makes a cut about 6-10 inches in front of the knee. The knee cap is pushed aside and the affected part of the joint is removed and replaced by the implant.

In general, this can be broken down into the following steps:

Removal of the damaged part: The damaged cartilage forming joint surface of the femur (thigh bone) and tibia (shin bone) are removed along with a small part of the adjacent bone.

Fixation of the implant: The metal implants are then fixed in place by means of press-fit or with the help of adhesive material called bone cement.

Implantation of the spacer: Then a plastic spacer is inserted between the metallic parts of the implant to form a smooth surface where these metal components can glide.

Knee cap resurfacing: In some cases, the undersurface of the kneecap is removed and replaced with a plastic surface.

Checking and skin closure: Before closing the skin again the doctor checks for proper functioning of the implant by bending and rotating the knee.

The surgery generally takes around 1-2 hours.

Recovery: After surgery, the person is shifted from OT to a recovery area where he/she is monitored for several hours while recovering from the effects of anesthesia. After this, the person is shifted to the hospital room.

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How long you have to stay in hospital and what treatment you would get?

After the surgery, you would stay in the hospital for several days. Generally, for 2-4 days before you can be considered fit to go to your house. The main aim of the hospital stay is to monitor the recovery of the person and to prevent any immediate complications after surgery.

During the stay, you would receive medicines and physical therapy to relieve your symptoms and allow early recovery. The doctor would also teach you how to take certain precautions and do several exercises to attain better and early functionality without any complications.


Antibiotics– given before, during, and after surgery to avoid infection.

Pain killers– to manage pain felt after surgery. Preferable to give non-opioids medicines to avoid addiction associated with opioids pain killers. Sometimes opioids are given in the initial period.

Antacids and other medicines to control acidity.

Blood thinners– to prevent formation of clots in the blood vessels of the legs.

Physical therapy and exercises:

It starts immediately after surgery. The doctors would encourage you to move your foot and ankle. Following this on the same day or day after you would be also encouraged to stand and walk.

Doctor might also use a device that covers your leg and compresses it to push the blood back towards the heart and thus prevent blood clotting. This device is used while the person is lying down and is called a compression boot.

When the person starts walking, the doctor may provide with anti-embolism stocking that covers foot, ankle, leg, and knee-tight enough to prevent stagnation of blood and formation of the clot.

Rehabilitation program:

The physical therapist will start your rehabilitation program by showing you some exercises and asking you to perform them regularly.

The aim of rehabilitation is to increase the strength of the muscles and to attain a good range of motion. This in turn allows the best functioning possible with the replaced knee. It also guides you in what not to do like avoiding overstraining the knee during the recovery period and to set achievable goals during this period.

A person can start with regular daily activities in 3-6 weeks like walking, going for shopping, etc, and after few months one is able to live an active lifestyle doing more complex activities like swimming and riding a bicycle.

High-impact activities and sports such as running, or playing football are to be avoided which could result in early implant failure and other complications.

Following a healthy lifestyle with a good diet, keeping weight under control, and avoiding smoking helps in minimizing implant-related complications.

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What studies suggest about the success rate of a hospital/expert for knee replacement?

Studies suggest that the success of joint replacement partially depends on the experience of the surgeon and the care facility. One study showed better results in people who operated by a surgeon who had performed more than 6 knee replacements every year and in a hospital setup where more than 25 replacements were performed per year. Surgery with good results is indicative of better knee functioning and less chances of complications.

What are the risk factors/complications associated with knee replacement and how common they are?

The complications associated with knee replacement are low with serious complications seen in less than 2% of patients. Life-threatening conditions like heart attack and stroke occur in even less number of patients.

Blood clots

Clot formation in veins of the leg is one of the commonest complications of knee replacement. The person develops pain and swelling in the leg. This generally happens as a result of stagnation of blood within the leg vessels due to immobility.

This can get further complicated and become life-threatening when the clots detach itself from the leg veins and travel to the lungs. The person would develop difficulty in breathing, chest pain, or cough.

To prevent this doctor would ask to do the following:

• Periodic elevation of legs
• Lower leg exercises/physiotherapy to increase the flow in the leg vessels
• Support stockings to prevent stagnation of blood and
• Medicines to keep the blood thin

In case a person feels any of these symptoms, he/she should immediately consult the doctor


can happen during the hospital stay in the post-op period or several days to years after surgery at home also. It can happen in the wound or around the prosthesis within the bone. Superficial infection in the wound can be treated with antibiotics and regular wound care. Whereas deep infection within the bone may need repeated surgery with removal of the prosthesis.

Signs of infections

– Fever more than 100 F

– Fever with chill and shivering

– Local changes around the knee joint with the development of swelling, redness, and pain getting worse with time.

– Oozing of fluid/pus from the surgical site.

– These signs should be taken seriously and should warrant consultation with the doctor.

Other complications

• Injury to vessels and nerves around the knee- Rarely seen.

• Heart attack- very rare.

• Stroke- very rare.

• Continued pain. A small proportion of people experience pain continuing even after knee replacement or feel dissatisfied. However, the majority of them, approx. 90% suggest significant relief in their symptoms.

Implant problems

– Stiffness: Occasionally, despite physical therapy, a patient’s knee may get stiff and may not bend or straighten properly. If this occurs, then the patient may return to the operating room in order to bend and/or straighten the knee under anesthesia.

– Early failure: Although most studies demonstrate that 80 to 90 percent of total knees will last between 15 to 20 years, early failures may occur due to a variety of reasons. These include loosening of the implants, infection, fractures of the bone around the implants, and instability. When early failures occur, revision surgery may be necessary.

– Artificial knees can wear out: Another risk of knee replacement surgery is the failure of the artificial joint. Daily use wears out even the strongest metal and plastic parts. Joint failure risk is higher if you stress the joint with high-impact activities or excessive weight.

– Implant problems: Although implant designs and materials, as well as surgical techniques, continue to advance, implant surfaces may wear down and the components may loosen. Additionally, although an average of 115° of motion is generally anticipated after surgery, scarring of the knee can occasionally occur, and motion may be more limited, particularly in patients with the limited motion before surgery.

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What are other treatment options available before opting for knee replacement surgery?

It is advisable to go for non-surgical methods before opting for a knee replacement which is considered when these treatment options fail to give substantial relief in symptoms.

Nonsurgical treatment

These are the first line of treatment given for patients presenting with chronic knee pain:

• Weight loss – This is one important way of reducing ongoing continuous wear and tear on the knees inflicted by the body weight. It can be very helpful in overweight and obese people having knee problems. The fact that knee bears about 4 pounds of pressure for every pound of bodyweight indicates the role of body weight in managing knee problems. Thus, even a slight proportion of weight loss can be really helpful to reduce pain and progression of the knee problem.

• Exercise/physiotherapy– another way of reducing physical stress on the knee joint is to strengthen the muscles around the knee which act as an important pillar for bearing weight. Thus, it helps to take off pressure from the cartilage and bones of the knee joint. Movement of the joint also prevents the joints from getting stiff.


• Oral: These include oral pain killers and anti-inflammatory drugs. These include drugs like acetaminophen/ paracetamol, ibuprofen, or naproxen. These can cause side effects seen commonly associated with oral NSAIDs and pain killers especially if taken for a long duration and without any medical supervision.

• Local applicants: Some local applicant cream and gel are also available which has pain-relieving and anti-inflammatory effects. These have benefits over oral drugs in terms of side effects as they are applied over the knee joint from where they are directly absorbed.

• Injections: This involves injecting a steroid to reduce inflammation and to relieve associated pain. The doctor may inject hyaluronic acid derivative or platelet-rich plasma to support healing.

Support and mechanical aid to knee joint:

Knee brace:: these are the devices worn around the knee joint which may help relieve symptoms. They may help by providing mechanical support to the knee, by aligning the knee and shifting the weight from the most damaged portion of the joint.

• Shoe inserts – There are lateral wedge insoles available that are put inside the shoe to tilt the outer part of the foot. These are used for the purpose of reducing the load on the inner part of the knee joint where the degeneration usually begins and tends to be more severe.

According to a review published in JAMA (Journal of the American Medical Association) in 2013, the shoe inserts have little than any substantial effect to relieve pain in patients of already established osteoarthritis. Harvard health letter suggests considering flexible shoes with flat heels which more closely imitate the movement of walking barefoot, with a cane to boost your stability.

• Cane or walker can be used to provide stability and support.

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What are the different types of knee replacement surgery that can be done?

When we say knee replacement the commonest type of surgery performed is total knee replacement where both inner and outer components of tibial and femoral joint space are replaced with or without patellar surface. This can have further variations:

• Posterior cruciate ligament (PCL) substituting: One of the most commonly done procedures. This surgery is done when PCL (the ligament that supports knee joint when bent) is not healthy enough to support an artificial implant. Instead of PCL, an implant component called “camp and post” is used to support the knee on bending.

• Posterior cruciate ligament (PCL) retaining: is done when PCL is healthy enough to support an artificial implant. This is thought to provide more natural bending.

• Bicruciate (ACL and PCL) retaining: both ACL and PCL are retained to try to achieve knee functioning close to the original knee. Bicruciate-retaining components are relatively new and there are not yet many studies to suggest the pros and cons.

• Partial knee replacement/Uni-compartmental replacement: less commonly done. It is done in some patients where only one of the three compartments of the knee joint (two between tibia and femur and one between patella and femur) is affected which can be replaced by smaller implant put in the concerned compartment. There is controversy regarding its advantage over total knee replacement, however, some studies have shown favorable results.

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What different materials are used in implants and how it impacts implant selection?

Implants can be made of metal, ceramic, and high-grade plastic. There are different types of implants based on the material used for making different components of an implant.

In general, it has femoral and tibial components at two ends with a spacer in between two provides a smooth surface for gliding. In some cases, the plastic component is put along the joint surface of the knee cap (patella). The implants are as follows:

1. Metal on plastic: This is the commonest type of implant used. It consists of a metal femoral and tibial component with a plastic spacer placed in between attached to the tibial component. Metals implants are commonly made of cobalt-chromium, titanium, zirconium, and nickel. It is the least expensive and considered highly safe and durable.

2. Ceramic on plastic: Femoral component is made of ceramic or metal covered with ceramic. The spacer is made of plastic. It can be used in patients sensitive to nickel.

3. Ceramic on ceramic: The femoral and tibial components are made of ceramic. Ceramic amongst all components is least likely to react with the body.

4. Metal on metal: Both the components- the femoral and the tibial components are made of metal.


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