Total knee replacement surgery, also called total knee arthroplasty (TKA), replaces the damaged surfaces of the knee joint with artificial components. It is commonly performed when advanced arthritis has caused persistent pain, stiffness and difficulty with movement that has not improved sufficiently with non-surgical treatment.
During the operation, the surgeon removes the damaged surfaces at the ends of the thighbone and shinbone and replaces them with carefully sized artificial components. The underside of the kneecap may also be resurfaced depending on the condition of the joint and the surgical plan.
The aim is to create a stable, well-aligned knee that can move smoothly and reduce the pain caused by the damaged joint. If you want to understand the broader treatment, you can also explore our guide to Knee Replacement Surgery.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
What happens before total knee replacement surgery?
The operation begins before you enter the operating room. Your orthopaedic and anaesthesia teams review your medical history, medicines and general health. The surgical team confirms the knee being operated on and discusses the planned procedure with you.
You may also undergo preoperative tests to make sure you are medically prepared for surgery. The surgeon reviews your knee imaging and plans the size and positioning of the replacement components based on your individual anatomy.
Step 1: Anaesthesia is given
Total knee replacement can be performed under general anaesthesia, where you are asleep, or under spinal anaesthesia, which numbs the lower part of your body. Sedation may also be used with spinal anaesthesia. The choice depends on your health, the anaesthetist's assessment and the circumstances of the operation. Your heart rate, blood pressure, oxygen levels and other vital signs are monitored throughout the procedure.
Step 2: The knee is prepared for surgery
Once anaesthesia has taken effect, the leg is positioned and the skin around the knee is thoroughly cleaned with an antiseptic solution. The surgical area is covered with sterile drapes so that the operation can be performed under controlled conditions.
In some operations, a tourniquet may be used around the thigh to temporarily reduce blood flow to the surgical area. Its use depends on the surgeon and the individual procedure.
Step 3: The surgeon makes an incision
The surgeon makes an incision at the front of the knee to gain access to the joint. The tissues around the knee are carefully moved aside so the damaged joint surfaces can be reached.
The kneecap, or patella, is moved to the side to provide access to the joint behind it. This allows the surgeon to see and prepare the ends of the thighbone and shinbone.
Step 4: The damaged surfaces of the thighbone are removed
The lower end of the femur, or thighbone, forms the upper part of the knee joint. In severe arthritis, this surface may be worn and irregular. The surgeon removes the damaged portion using specialised surgical instruments and bone-cutting guides.
The bone is shaped carefully so that it can accommodate the femoral component of the artificial knee. The amount of bone removed is carefully controlled. The surgeon also considers alignment and the balance of the surrounding soft tissues when preparing the knee.
Step 5: The damaged surface of the shinbone is prepared
The upper end of the tibia, or shinbone, forms the lower part of the knee joint. The damaged surface is removed and the bone is shaped to receive the tibial component of the replacement.
The surgeon uses measurements and alignment guides to prepare the bone for the correct size and position of the implant. Proper positioning is important because the components need to work together as the knee bends and straightens.
Step 6: The kneecap may be resurfaced
The underside of the kneecap can also be affected by arthritis. Depending on the patient's knee condition and the surgeon's approach, the underside of the patella may be resurfaced and fitted with a plastic component.
This is not identical in every total knee replacement. Whether the patella is resurfaced depends on factors such as the condition of the kneecap and the surgical plan.
Step 7: Trial components are positioned
Before placing the final implants, the surgeon may insert trial components. These temporary components allow the surgical team to assess how the new knee fits and moves before the permanent implants are inserted. The surgeon checks factors such as:
- Knee alignment
- Stability
- Range of movement
- Balance of the surrounding soft tissues
- How the components move together
Step 8: The artificial knee components are inserted
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Once the knee has been appropriately prepared and the trial components provide satisfactory movement and stability, the final implants are positioned. A typical total knee replacement includes:
- Femoral component: a metal component that replaces the damaged surface at the lower end of the thighbone
- Tibial component: a component that covers the prepared upper surface of the shinbone
- Polyethylene insert: a durable plastic bearing positioned between the femoral and tibial components
- Patellar component: a plastic component that may be placed on the underside of the kneecap when resurfacing is performed
How are the implants fixed to the bone?
The components can be secured to the bone using different fixation methods. One commonly used approach involves bone cement, which helps secure the implant to the prepared bone.
Some implants are designed for cementless fixation. Their surfaces allow bone to grow onto or into the implant over time, helping establish fixation. The choice depends on factors such as bone quality, implant design, patient characteristics and the surgeon's assessment.
Step 9: The new knee is tested
After the final components are placed, the surgeon moves the knee through its range of motion and assesses its stability.
This is an important part of the procedure because the new joint needs to function properly not only when the leg is straight but also when the knee bends.
The surgeon checks that the components are appropriately aligned and that the surrounding tissues provide suitable stability. If necessary, adjustments can be made before the wound is closed.
Step 10: The incision is closed
Once the surgeon is satisfied with the position and function of the replacement, the tissues are repaired and the skin incision is closed. Depending on the surgical technique, the incision may be closed with stitches, staples or another closure method. A sterile dressing is placed over the wound.
What happens immediately after the operation?
After surgery, you are taken to a recovery area where the medical team monitors you as you wake from anaesthesia. You may receive medicines to control pain and nausea. The surgical team also checks your wound and overall condition.
Once you are stable, you are transferred to the appropriate hospital ward or recovery area. Recovery does not wait until the next day. Physiotherapy and gentle movement generally begin early after total knee replacement.
What happens to the original knee joint?
A total knee replacement does not mean that the entire knee is removed. Instead, the surgeon removes and resurfaces the damaged joint surfaces of the femur and tibia and replaces them with artificial components.
The ligaments and other soft tissues are managed according to the implant design and the surgical technique. The aim is to preserve or appropriately balance the structures needed to provide a stable, functioning knee.
Is the kneecap always replaced during total knee replacement?
No. The underside of the kneecap may be resurfaced with a plastic component, but this is not performed identically in every patient. The decision depends on the condition of the patella, the patient's anatomy and the surgeon's assessment.
Does total knee replacement completely restore a natural knee?
The goal of total knee replacement is to relieve pain and improve function, but an artificial knee is not identical to a natural knee. Many patients experience substantial improvement in pain and mobility after recovery, but the knee may feel different from a natural joint.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Some people notice sensations such as clicking or awareness of the artificial components, particularly during certain movements. Recovery and rehabilitation also influence how well the knee functions after surgery.
The Bottom Line
Total knee replacement is a carefully planned procedure in which the damaged surfaces of the knee are replaced with artificial components. The surgeon prepares the femur and tibia, may resurface the underside of the kneecap, tests temporary components, places the final implants and checks the new knee for appropriate movement and stability before closing the incision.
The operation itself commonly takes around one to two hours, but the overall surgical experience includes preparation, anaesthesia and postoperative monitoring. Recovery begins soon afterward, with patients usually starting gentle movement and walking with assistance.
The replacement is designed to provide a stable, functional joint with substantially less pain from the damaged arthritic surfaces. However, the artificial knee is not identical to a natural knee, and the final result depends not only on the surgery but also on rehabilitation and gradual strengthening.
Understanding each stage of the procedure can make total knee replacement feel less unfamiliar. The operation may involve several technical steps, but the overall purpose is straightforward: remove the damaged joint surfaces, accurately position the replacement components, restore a stable moving joint and begin the process of rehabilitation.
