The most common cause of chronic knee pain and disability is arthritis.There are three kinds of arthritis:
Osteoarthritis - commonly known as 'wear and tear arthritis' or degenerative arthritis since the cartilage simply wears out. When cartilage wears away, bone rubs on bone causing severe pain and disability.
Rheumatoid Arthritis - occurs due to inflammation of the joint lining, resulting in erosion of the articular cartilage and eventually damaging the knee joint surface. Traumatic Arthritis - is caused by a serious knee injury or severe tears of the ligaments in the knee.

In a Total Knee Replacement process, the implanted prosthesis is made up of four parts:
The tibial component has two elements that replace the top of the shin bone or tibia.The prosthesis is formed of metal tray which is attached directly to the bone and a high-density plastic spacer that provides the bearing surface. The femoral component replaces the bottom of the thigh bone or femur and the groove where the patella or knee cap rides. This component is made of cobalt chrome, a metal alloy known for its toughness and biocompatibility. The patellar component substitutes the surface of the knee cap, which rubs against the femur. The resurfaced patellar button slides smoothly on the front of the joint and also protects it. The surgeon determines during the surgery if it requires a replacement or not. The patellar component is made up of a durable plastic.

If all other conservative measures have failed and there is severe arthritic pain, you should seriously consider Total Knee Replacement Surgery. It also effectively improves joint stability, corrects bone deformity and alignment, and significantly enhances your quality of life. While the idea of getting an artificial knee joint may be frightening to some, it is one of the safest and most effective medical procedures performed on more than 600,000 people worldwide each year. It has, in fact, become one of the routine procedures, especially with the recent advancements in surgical techniques and implant design. What's more, your implant can now last for two decades or more, giving you years of active, healthy and pain-free life.

You'll be instructed by your surgeon to perform pre­admission activities such as pre-operative X-rays and a thorough investigation into your past medical history. This will be followed by a complete physical examination and a physical therapy programme to ensure you are fit for surgery.Your surgery may require blood replacement through transfusion and you can opt to donate your own blood a few days prior to surgery. If the surgeon feels you will benefit from an evaluation with the anaesthesiologist ahead of time, it will be arranged before your surgery. Further, you'll be advised not to eat or drink anything in the night before the day of surgery.

A number of activities will take place on the day of surgery. You will most likely be admitted to the hospital, a day prior to the surgery. A final assessment of vital signs will be made and you'll be given a clean hospital gown. An intravenous (IV) will be fitted to give you fluids and medication during and after the surgery. An elastic stocking may be given to you to reduce the chances of blood clots. All jewellery, dentures, contacts and nail paint would be removed and you'll be instructed to empty your bladder.Your surgical leg will be scrubbed and shaved to prepare you for surgery. And  before taking you  into the operation theatre, your anaesthesiologist will evaluate which type of anaesthesia will be best for you.

After your surgery, you will be shifted to the recovery room for close observation of your vital signs, circulation and sensation. Initially, you will have a bulky dressing around the knee and a drain placed near your incision in order to record the amount of fluid being lost from the wound. You may be wearing an elastic hose and/or a compression stocking sleeve designed to minimise the risks of blood clots. Your doctor may prescribe a PCA (Patient Controlled Analgesia) through an intravenous (IV) connection so that you can regulate the amount of pain relief medication you need. You may be fitted with a urinary catheter in the bladder as the side effects of anaesthesia often make it difficult to urinate for a few hours after the surgery. And a knee immobiliser may be given to protect your knee when you stand up.

Following surgery, you will be evaluated and treated by a physical therapist. You need to diligently work on the rehabilitation process, to achieve optimal clinical and functional goals.You should adhere to following goals during rehabilitation process:
In the hospital:
A Continous Passive Motion (CPM) machine if required will be attached within a day or two after surgery to aid in the progressive flexion of your knee. You will start walking, using a walker and crutches (weight-bearing status will be determined by the surgeon). You'll be instructed to perform a variety of motion exercises. An edema control (ice, compression, elevation) will be performed and you will get the guidelines for home exercise program.
Discharge from hospital:
Before you go home, you should be independent in getting in and out of bed.You should be able to walk independently with walker or crutches and comfortable in walking up and down 3 steps without assistance. You should be at ease in doing your home exercise by yourself. You should also be able to fully straighten your knee and bend it upto 90 degrees.
Outpatient physical therapy:
A physical therapist will teach you specific exercises to strengthen your leg and restore knee movement. These exercises will include advanced strengthening programme, adding weights along with stationary cycling, walking programme and aquatic therapy programme.
Long-term rehabilitation goals:
The long-term aim of rehabilitation is to ensure the range of motion of knee flexion from 100-120 degrees. There should be minimal or no pain while walking or doing other low-impact physical activities and you should be independent to perform all activities of daily life.