Purpose:
A knee replacement surgery is usually performed in the following cases:

1.Osteoarthritis: 
This type of arthritis (inflammation of the joint) is age-related.
It is caused by the normal wear and tear of the knee joint.
It usually affects people over 50 years of age, but younger people may also have it.
The condition is caused by inflammation, breakdown, and gradual and eventual cartilage loss in the joints.
The cartilage wears down over time and the bones tend to rub together. The bones often grow thicker to compensate for this, but this may cause more friction and pain.

2. Rheumatoid arthritis:
This condition is also known as inflammatory arthritis.
The membrane around the knee joint becomes thick and inflamed in this condition.
Chronic or long-term inflammation causes damage to the cartilage, leading to stiffness and soreness.

3. Post-traumatic arthritis:
This type of arthritis occurs due to a severe knee joint injury.
When the bones surrounding the knee joint break or the ligaments tear, it affects the knee cartilage.

Symptoms:
Knee surgery may be needed in patients who experience:

• Severe knee stiffness or pain that prevents a person from carrying out daily activities, like walking, getting up from a chair, going upstairs, and getting in and out of cars.
• Moderate, continuous knee pain that occurs even while sleeping or resting.
• A knee deformity, where a noticeable arch is seen on the inside or outside of the knee.
• Chronic or long-term knee inflammation and swelling that does not improve even on resting or taking medicines.
• Depression, due to an inability to carry out social or other daily activities.
• If other treatment methods fail to work

Diagnostic procedure:

1. Physical examination: The surgeon will assess the symptoms of the patient. The complete medical history of the patient is evaluated. The surgeon will also assess the soft tissues and the mobility of the knee joint.
2. Blood tests: These tests help to check for infections and check for the presence of certain medical disorders, along with the blood clotting time and presence of inflammation in the body.
3. Urine tests: These tests help to check for infection, diabetes, and other medical diseases.
4. Electrocardiogram (ECG): This test is done to check the electrical activity of the heart and check for other heart conditions.
5. Chest x-ray: It helps to check the heart and lung condition.
6. Imaging tests: X-rays, CT scans, and MRI scans help in providing a clear image of the bone defect present in the knee area, which may influence the type of implant that should be used in the knee replacement surgery.
   

The procedure is generally performed under general anesthesia (the patient is made unconscious during the procedure) or epidural anesthesia (the patient is numbed waist downwards).
The surgical site is cleansed with an antiseptic solution.

The knee joint can be approached by the doctor using any one of the following techniques:

1. Traditional open surgery: The procedure involves the doctor making an 8-to 12-inch incision or cut to enter the knee area.

2.Minimally-invasive surgery: The procedure involves making a small 3-to 4-inch incision and pushing the kneecap to the side rather than turning it over. This requires a smaller incision and lesser trauma than open surgery. It also causes fewer complications and has a quicker recovery than open surgery. The different types of minimally-invasive surgeries are:
a) Quadriceps-sparing approaches: After making a small incision, the surgeon shifts the patella to the side to cut away the arthritic bone without cutting through the quadriceps tendon and causing less trauma to the quadriceps muscle (muscles present in the leg region).
b) Lateral approach: It is a rarely used technique performed in patients whose knees tend to bend outwards. The surgeon will approach the knee from the side rather than the front.
c) Computer-assisted surgery: The procedure involves entering the patient’s anatomical data into a computer, a procedure known as registration, and allowing the computer to generate a 3D model of the knee joint to provide the surgeon with a more precise image of the knee joint and help in a more accurate alignment of the knee joint.

• The doctor then removes the damaged surfaces of the knee joint and the knee joint is resurfaced with the prosthesis.
• The knee prosthesis is usually made up of plastic or metal.
• The most common type of artificial knee joint prosthesis used is a cemented prosthesis. Uncemented prosthesis are usually not used.
• A cemented prosthesis is attached to the bone with surgical cement.
• An uncemented prosthesis is attached to the bone with a porous surface onto which the bone tends to grow and attach to the prosthesis.
• Sometimes, the doctor may use a combination of cemented and uncemented prosthesis to replace a knee.
• The incision is then closed using stitches or surgical staples.
• The doctor may place a drain in the incision site to remove the fluid.
• A sterile bandage or dressing is then applied to the incision site.

The following complications are associated with knee replacement surgery:

• Infection
• Deep vein thrombosis (blood clot formation in the legs)
•  Pulmonary embolism (blood clot in the lungs)
• Continued stiffness or pain
• Nerve damage, causing weakness or numbness
• Fracture during or after surgery
• Allergic reaction to the bone cement
• Excess bone formation around the artificial knee joint, causing restricted movement in the knee
• Excessive scar tissue, which restricts the movement of the knee joint
• Kneecap instability, causing painful discoloration to the outer portion of the knee
• Dislocation of the kneecap
• Artery, ligament, or nerve damage around the knee joint
• Bleeding in the knee joint
• Wearing down of the implant surfaces, leading to the loosening of the components
• Need for a further surgery of the replacement wears out or becomes loose, if the person has a fall, or in case of a severe infection

• The patient is usually kept in the hospital for one to three days after the procedure.
• It is normal to have some pain after the surgery, but it is advisable to walk around with a walking aid as much as possible.
• Physiotherapy sessions aim at strengthening the knee. Although these sessions may be painful, they significantly reduce the risk of developing future complications.
• The patient can usually drive again four to six weeks after the surgery.
• The patient can usually resume work and other daily activities six to eight weeks after the procedure.
• Physiotherapy sessions may be needed for up to three months.
• Complete recovery from the surgery takes approximately three months. The muscles and scar tissues may still be healing for the next two years.
• The patient may be recommended iron supplements in the interim to help in wound healing and improving muscle strength.
• It is advisable to avoid heavy lifting and bending down for a few weeks after the surgery.
• Avoid standing still for long periods, as it may cause ankle swelling.
• The patient is advised to use crutches, a walker, or a walking stick until the knee is strong enough to take the person’s body weight.
• The patient needs to take all the medications advised by the doctor regularly.
• It is advisable to keep the affected leg raised on a footstool when sitting.
• Avoid soaking the wound until the scar heals completely, to prevent infection.
• It is advisable to monitor the symptoms of infections or blood clots and visit the doctor immediately if these symptoms are noticed.
• Take precautions to avoid a fall or injury, as it may lead to the need for further surgery. 
• Avoid extreme sports during the recovery period. Low to moderate-impact sports or activities, like walking swimming, and biking can be done.