Knee replacement surgery

A total knee replacement, or total knee arthroplasty, is an operation to remove damaged parts of the knee joint and replace them with artificial parts. The aim of the surgery is to relieve pain and restore function to the joint.

This is a common operation undertaken in New Zealand as elective (non-urgent) surgery in both public and private hospitals, typically involving a few days’ hospital stay.

Why have knee replacement surgery?

Severe knee pain or stiffness that limits daily activities (e.g. walking, climbing stairs, getting in and out of chairs) is the main reason that knee replacement surgery may be recommended. Other reasons are knee pain even while stationary, and knee deformity. These problems are likely the result of osteoarthritis or rheumatoid arthritis.

Most people who undergo total knee replacement surgery are between 50 and 80 years of age. However, eligibility for knee replacement surgery is primarily based on a person’s level of pain and disability, not their age.

An orthopaedic surgeon will assess the need for a knee replacement taking into account a person’s medical history and symptoms, physical examination (especially knee range of motion, stability, strength, and alignment), and imaging of the knee.

Risks of surgery

As with any surgical procedure, there are risks involved with a total knee replacement. As well as general risks of infection and risks associated with anaesthesia, risks specific to this surgery include:

• Blood clots can form in one of the deep veins in the leg (deep vein thrombosis or DVT)
• Nerves can be injured from swelling or pressure resulting in permanent pain, numbness, or loss of function
• The knee prosthesis may become loose and require further surgery.

The surgery

An artificial knee joint (prosthesis) has smooth surfaces that replace the worn surfaces within the knee joint. The prosthesis is made of metal alloys and hard plastic components that are fitted together during surgery.

Knee replacement surgery can be performed under a spinal or general anaesthetic. This will be discussed with the surgeon and anaesthetist prior to surgery and a decision made as to which is most appropriate.

Surgery begins with an incision being made over the front of the knee joint, loosening of the muscles and ligaments surrounding it, and turning the kneecap out of its place. The worn surfaces within the joint are removed and the ends of the bones are precisely cut. The components of the artificial knee joint are then attached to the bone ends. The muscles and ligaments are repositioned and, if necessary, the ligaments are adjusted to achieve the best possible knee function. The surgeon then closes the layers of tissue and the skin with stitches and a dressing is placed around the knee.

Antibiotics are usually given during and after the operation to prevent the development of infection in the new joint.

Measures to prevent the formation of blood clots and reduce leg swelling may be prescribed. These may include compression stockings, inflatable leg coverings (compression boots), and blood thinning medication. Foot and ankle movement is encouraged following surgery to boost blood flow in the leg muscles, which also helps to prevent leg swelling and blood clots.

Following surgery

After surgery, your surgeon and a physiotherapist or physical therapist will provide recovery and movement guidelines. The success of the surgery depends on following these recovery and movement instructions.

Crutches may need to be used in the initial period after the operation. After 6 weeks, most people should be able to return to a range of normal activities, including driving.

It is usual to see the surgeon 2 to 6 weeks after surgery to assess recovery. Long-term follow up may also be recommended. It may be that replacement (revision) of the artificial knee joint is required if complications occur.

Excessive activity or weight speeds up the normal wear of the replacement joint and may cause it to loosen and become painful. Low-impact activities, such as walking, swimming, playing golf, light hiking, cycling, and dancing, may be recommended.

References

American Academy of Orthopaedic Surgeons (2020). Orthoinfo: Total knee replacement (Web Page). Rosemont, IL: American Academy of Orthopaedic Surgeons. https://orthoinfo.aaos.org/en/treatment/total-knee-replacement [Accessed: 30/06/21]
Mayo Clinic (2020). Knee replacement (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/tests-procedures/knee-replacement/about/pac-20385276 [Accessed: 30/06/21]
NHS (2019). Knee replacement (Web Page). Redditch: National Health Service (NHS) England. https://www.nhs.uk/conditions/knee-replacement/ [Accessed: 30/06/21]
Palmer, S.H. (2020). Total knee arthroplasty (TKA) (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/1250275-overview [Accessed: 30/06/21]

Last Reviewed – June 2021

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