The knee is one of the complex joints in the body. It connects the thighbone (femur) and the shinbone (tibia). The knee joint is actually two joints. The major joint is between the thigh bone (femur) and the shin bone (tibia). The smaller joint is between the kneecap (patella) and the thigh bone (femur).
A smooth, tough tissue called articular cartilage covers the ends of the bones, allowing them to slide smoothly over each other. The synovial membrane is a bag that covers the surfaces of the knee joint and produces synovial fluid that lubricates the joint.
If the articular cartilage becomes damaged, the ends of the bones rub together, causing pain and difficulty in moving the knee joint. A severely damaged joint may become stiff, and difficult to move. The combination of pain and stiffness may impact the quality of life. Painkillers may provide temporary relief but may not improve the joint function. This dysfunctional knee may need replacement in order for the person to be able to walk again.
The knee joint, like all other tissues in the body, is subjected to the normal wear and tear that over time may damage the bones and their surfaces. In addition, conditions such as arthritis may also affect the joint by causing changes due to inflammation.
Knee replacement or arthroplasty is surgery to replace a damaged, worn or diseased knee with an artificial joint. The goal of knee replacement is to relieve pain, restore proper function of the knee joint and improve the quality of life.
Knee replacement surgeries are of two types the choice of which is decided by the degree of dysfunction of the joint.
- Total knee replacement
- Partial knee replacement
In this procedure, the complete knee joint is replaced with an artificial joint, made of metal and plastic components. The procedure may be chosen for obese patients and those who have a severe joint dysfunction.
The damaged ends of the thigh bone (femur) and shin bone (tibia) are carefully cut away. The ends are precisely measured and shaped to fit the appropriately sized prosthetic replacement. The end of the femur is replaced by a curved piece of metal, and the end of your tibia is replaced by a flat metal plate. These are fixed using special bone ‘cement’, or are specially treated. A plastic spacer is placed between the pieces of metal. This acts like cartilage, reducing friction as the joint moves. The back of the knee cap may also be replaced, depending on the condition of the joint.
The joint should last around 15-20 years.
If only one side of the knee is damaged, a partial knee replacement (PKR) may be recommended. PKR is a less extensive operation, with a smaller incision, and involves less bone being removed.
The advantages to PKR include a shorter hospital stay and recovery period. PKR often results in more natural movement in the knee and you may be able to be more active than after a total knee replacement.
However, the pain relief with PKR is not always as good as with a total knee replacement and it does not usually last as long, which is likely to mean further surgery at a later date. It is less suitable for a young, active person.
The surgeon may use the latest technology such as computer assisted surgical treatment. The surgeon performs this operation using computerized images tracked on infrared cameras in the operating theatre. This will enable the new knee joint to be positioned more accurately. During this procedure, the surgeon makes minor incisions to help access the joint. With this, the recovery is quicker with a shorter hospital stay.
Minimal Incision Surgery: The surgeon makes a smaller cut than in standard knee replacement surgery. Specialized instruments are then used to manoeuvre around the tissue, rather than cutting through it. This should lead to a quicker recovery.
All surgeries have their own risks and complications. The risks associated with the knee replacement surgery include:
- Though anaesthesia is generally safe, there are risks associated with it.
- There is the risk of developing VTE or venous thromboembolism because of reduced movement around the time of surgery. Precautions will be taken to prevent this with special support stockings and anticoagulant medicines.
- Risk of developing an infection of the wound
- Risk of unexpected bleeding, ligament or nerve damage around the joint
- There may be a fracture caused in the bone around the joint
- There may be an allergic reaction to the cement
Stay as active as you can. Strengthening the muscles around your knee with gentle exercise such as walking and swimming, in the weeks and months before surgery, will aid your recovery. Your physiotherapist will give you helpful exercises.
There are some things that you need to do before surgery. These include:
- Getting a medical checkup and tests such as blood and urine tests, ECG, x ray and any other test to make sure you are healthy enough for an anaesthetic and surgery.
- Have a list of any medication you are taking, as these may need to be stopped on your doctor’s advice and alternatives prescribed if required. They include some rheumatoid arthritis medications that suppress the immune system, which can affect healing as well as any anticoagulant medication.
After surgery you will be moved to the Recovery Room where you will be closely monitored for a few hours. You may feel some after effects of anaesthesia such as a sore throat, vomiting and drowsiness but you will be made as comfortable as possible.
You will have pain for a few hours after the surgery which be relieved with painkillers that may be given either through an epidural injection or as injectable medication.
To avoid the risk of blood clots you should start moving around as soon as possible. Lying in bed for too long can cause some of your blood to pool in your legs. Try to exercise your legs in simple ways such as by flexing your ankle and rotating your foot. You may be given special support stockings to wear after surgery to help your blood circulation. Some people are given an injection to thin the blood slightly to help reduce the risk of clots.
You will be given passive motion exercises 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.
The earlier you get out of bed and start moving the faster the recovery. Your physiotherapist will assist you with this. You can start walking within 24 -48 hours after the surgery by using an assistive device and with the help of the physiotherapist. It is normal to experience initial discomfort while walking and exercising, and your legs and feet may be swollen.
The exercises your physiotherapist gives you are an important part of your recovery. It is essential you continue with them once you are at home.
Swelling may appear after the surgery, and it may last for as long as six months. Stiffness may partly be because of the swelling. Ice packs 5 times a day for 5 minutes each time would help as well as the anti-inflammatory medication prescribed by your doctor.
Before discharge you will be advised about exercises you need to do, how to care for your wound, how to manage the pain, and any equipment you may require, such as dressings, bandages, crutches and splints.
Your discharge will be affected by how quickly you recover after the surgery, generally patients are discharged between 4-6 days after surgery on one knee and between 8-10 days after surgery on both joints.
Do not stand for long periods as this may cause ankle swelling and avoid stretching up or bending down for the first six weeks.
You should be able to stop using your crutches or walking frame and resume normal leisure activities six weeks after surgery. However, it may take up to three months for the pain and swelling to settle down. It can take up to a year for any leg swelling to disappear.
Even after you have recovered, it is best to avoid extreme movements or sports where there is a risk of falling and avoid sitting on the floor and keeping the legs crossed.
The knee is the most used and therefore stressed joint in the body. The common causes of pain in the knee are injury, arthritis and infection.
This depends entirely on the nature of the problem. Sometimes knee pain can be treated through rehabilitation, and on occasion surgery may be required. It is important to consult a doctor for proper advice as soon as the symptoms are evident.
Total Knee Replacement is a procedure in which the parts of the bones that rub together are resurfaced with metal and plastic implants. Precision instruments are used to remove and replace damaged parts of the bone with implants. The surface of the femur is replaced with a rounded metal component that matches closely the curve of your natural bone. And the surface of the tibia/leg bone is substituted with a smooth plastic component
If your knee pain is so severe that it causes difficulty in walking and performing daily activities, knee replacement might be called for. However it is mandatory that these symptoms be taken to a doctor for an accurate diagnosis. Doctors try and delay the procedure for as long as possible by using non-invasive treatment. However if the disease is in an advanced stage, knee replacement is a means to achieve relief from pain as well as return to daily activities.
A complete physical check-up is required to rule out any medical problems that may interfere with your surgery. At this time the doctor will also review your medical history. Do not forget to inform the doctor about any medication that you may be taking. A few routine pre-surgery tests will also be performed. The surgery can result in blood loss which will require transfusion. So you might be asked to donate a few units of your own blood prior to surgery.
Prior to surgery an IV line will be inserted into your arm to administer medication during the operation. Thereafter anesthesia is administered in the OT. Once anesthesia has taken effect, the knee is scrubbed and sterilized. The surgery then begins with an incision to expose the knee joint. The surgeon then uses precision guides and instruments to remove damaged surfaces. The ends of the bones are then shaped to accept the implants. The implants are then fixed, and the incision closed. A sterile bandage is applied to the wound and routine post operative care will follow as anesthesia wears off.
Bone cement is used to secure the knee implants.
A specially designed rehabilitation routine will be started to help regain strength, balance and movement in the knee. 24 hours after surgery, you will be asked to stand. And in 48 hours, you will start to walk with support. You can expect to stay in hospital for 3 days after surgery. Your sutures will usually be removed before discharge, and you will be advised on exercises to continue at home.
On an average, patients walk with a cane in 6 weeks, and start to drive in 2 months. While the surgery will relieve you of pain and allow you to resume most normal activities, this does not include contact sports and activities that put excessive strain on your knees.
Patients can resume sexual activity as soon as they feel able. Again, the important consideration is avoiding excessive strain on the knee.
Longevity of the prosthesis depends on the patient’s activity levels, weight as well as the accuracy of the implant placement. Recent studies have found common implants to be functional in 96% patients even after 20 years. However it must be understood that implants are not as durable as the natural knee, and will eventually wear out and no assurance can be given about its longevity.