What is Knee Replacement Surgery

Knee replacement surgery, medically known as knee arthroplasty, is a procedure to replace the weight-bearing surfaces of the knee joint. The surgery involves cutting away damaged bone and cartilage from the thighbone, shinbone, and kneecap and replacing it with an artificial joint made of metal alloys, high-grade plastics, and polymers. The goal is to relieve pain and restore function in severely diseased knee joints.

Knee replacement is considered when conservative treatments, such as medication and walking supports, are no longer effective. This surgery is primarily used to alleviate pain caused by arthritis. Other conditions, such as knee injury or rheumatoid arthritis, may also necessitate a knee replacement.

Indications for Knee Replacement Surgery

Individuals experiencing knee pain and mobility issues are candidates for knee replacement surgery. Indications for this procedure include:


This is the most common reason for knee replacement. Osteoarthritis is a degenerative joint disease that causes the cartilage in the knee joint to wear away, leading to pain and stiffness.

Rheumatoid Arthritis

This is an autoimmune condition that causes inflammation of the synovial membrane and can lead to the destruction of both cartilage and bone within the joint.

Post-traumatic Arthritis

This can follow a serious knee injury. Fractures of the bones around the knee or tears of the knee ligaments may damage the articular cartilage over time, causing knee pain and limiting knee function.

Severe Knee Injury

Previous injuries to the knee, such as fractures or ligament tears, can necessitate knee replacement if they result in chronic pain and functional impairment.


Individuals may have a pronounced bowing in or out of the knee, causing discomfort and difficulty with movement.

Limited Movement and Chronic Pain

Patients for this procedure often have substantial pain and limited mobility, which affects their quality of life. This includes difficulty in walking, climbing stairs, and getting in and out of chairs.

Preparing for Knee Replacement Surgery

Proper preparation is necessary for the success of knee replacement surgery.

  • Medical Evaluation: Patients typically undergo a thorough medical evaluation, including blood tests, and possibly a cardiogram and chest X-ray, to ensure they are healthy enough for surgery.
  • Medications: Patients should inform their surgeon about all the medications they are taking. Some medications may need to be stopped or adjusted before surgery.
  • Physical Preparation: Strengthening the muscles around the knee through physical therapy before surgery can aid in recovery.
  • Home and Lifestyle Preparations: Arrange for assistance at home, modify the living space to avoid stairs, and install safety devices like handrails.
  • Fasting: In many cases, patients will be instructed to not eat or drink anything after midnight before the day of surgery.

Knee Replacement Surgery Procedure

The knee replacement surgery procedure involves several steps:

  1. Anaesthesia: The surgery begins with the administration of anaesthesia, which can be either general (patient is fully asleep) or spinal/epidural (patient is awake but numb below the waist).
  2. Incision: The surgeon makes an incision at the front of the knee to access the joint.
  3. Removal of Damaged Cartilage and Bone: Damaged cartilage surfaces at the ends of the femur and tibia, along with a small amount of underlying bone, are removed.
  4. Implant Positioning: The removed cartilage and bone are replaced with metal components that recreate the surface of the joint. These metal parts are cemented into the bone.
  5. Resurfacing the Patella: The undersurface of the kneecap (patella) may be cut and resurfaced with a plastic button.
  6. Inserting a Spacer: A medical-grade plastic spacer is inserted between the metal components to create a smooth gliding surface.
  7. Closing the Incision: The incision is closed with stitches or surgical staples.

Recovery and Rehabilitation

Recovery and rehabilitation can aid the success of a knee replacement surgery.

  • Immediate Postoperative Period: Patients typically begin mobilising within 24 hours of surgery. Hospital stays usually last from 1 to 4 days, depending on the individual’s health and recovery progress.
  • Physical Therapy: Starting physical therapy early can help regain strength and mobility. This usually begins in the hospital and continues at home or a rehabilitation facility.
  • Pain Management: Pain and swelling are common after surgery. Pain can be managed with prescribed medications and should gradually decrease as the knee heals.
  • Exercise and Activity: Activities should be gradually resumed. Walking should start with the help of crutches or a walker before progressing to unassisted walking.
  • Wound Care: Proper care of the surgical wound can prevent infection. Instructions on how to care for the wound will be provided.

Risks and Complications

Like all major surgical procedures, knee replacement surgery carries risks and potential complications. These risks are generally outweighed by the potential benefits.

  • Infection: Infection can occur at the wound site or around the prosthesis. It may require antibiotics or further surgery.
  • Blood Clots: Clots can form in the leg veins after surgery. It may cause serious complications if they travel to the lungs (pulmonary embolism).
  • Implant Problems: Although rare, there can be issues with the implant, such as loosening or wear over time, possibly necessitating a revision surgery.
  • Continued Pain: Some patients may continue to experience pain in the knee after surgery.
  • Nerve Damage: There is a small risk of nerve damage during surgery, which can cause numbness or weakness.
  • Stiffness: Some people may not achieve the expected range of motion after surgery.
  • Anaesthesia Risks: As with any surgery requiring anaesthesia, there are risks associated with reactions to the anaesthesia or breathing problems.
  • Medical Complications: These can include heart attack, stroke, and kidney failure, although they are rare.

Long-term Outcomes and Prognosis

The long-term outcomes and prognosis are typically favourable. Modern knee prostheses are designed with durability in mind, often lasting 15 to 20 years. Following the surgery, many patients experience pain alleviation and enhanced mobility, facilitating their return to routine daily activities. Though high-impact activities may be restricted post-surgery, patients can usually engage in low-impact exercises like walking, swimming, and cycling.

Some patients may require revision surgery in the future, as the longevity of implants has its limits.

Regular follow-up ensures the knee replacement remains in good condition and any concerns are promptly addressed.


Knee replacement surgery offers pain relief and improved mobility for those suffering from severe knee conditions. It involves replacing the damaged parts of the knee with artificial components, aiming to restore function and quality of life. The procedure is generally effective and long-lasting, particularly when coupled with comprehensive recovery and rehabilitation processes.