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Total knee joint replacement surgery

 
A total knee joint replacement (also known as total knee arthroplasty) is an operation to remove a severely impaired knee joint and replace it with an artificial joint. 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 3-6 day hospital stay.  If the operation is undertaken privately (i.e in a private hospital and paid for by the patient or through health insurance), the cost is likely to be between $15,300 and $28,000 inc GST(Health Funds Association 2013).  

General information

In a healthy knee, smooth cartilage covers the ends of the femur (thighbone) and the tibia (shinbone). The cartilage acts as a cushion between these weight-bearing surfaces and allows the bone ends to glide easily over one another, allowing for painless movement. Muscles and ligaments give side-to-side stability. A synovial membrane lines the joint and produces synovial fluid (a clear lubricating fluid) in order to lubricate the joint.

Knee pain and stiffness can be caused by factors such as wear and tear or injury which cause the progressive degeneration of cartilage (osteoarthritis) reducing its ability to serve as a cushion. The bone ends are allowed to rub together and become roughened and irregular. This causes pain and limits movement. Rheumatoid arthritis (inflammatory arthritis) can cause the joint to become inflamed and swollen as well as damaging the cartilage. Other problems with the knee, including poor alignment of the leg bones, can also lead to deterioration of the knee joint.

An orthopaedic surgeon will assess the need for a knee replacement taking into account medical history, physical examination and x-rays of the damaged knee. A knee replacement is a major operation and there are many things to discuss with the surgeon, including the risks and benefits of the surgery.   

The surgery

An artificial knee joint (prosthesis) has smooth surfaces which replace the worn surfaces within the knee joint. The prosthesis is made of metal and hard plastic components that fit together during surgery. The surgeon chooses the most appropriate prosthesis design for each individual.

There are three main components of an artificial knee joint – the femoral component (to replace the end of the femur), the tibial component (to replace the end of the tibia) and the patellar component (to replace the back of the kneecap). In total knee joint replacement surgery, all of these components are used. 

Knee joint 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. The surgeon will expose the knee joint, loosen the muscles and ligaments surrounding it, and turn the kneecap out of its place. The worn surfaces within the joint, including the back part of the kneecap, are removed and the ends of the bones are precisely reshaped. The components of the artificial knee joint are then attached to the bone ends using specialised bone cement, and fitted together. The muscles and ligaments are repositioned and, if necessary, the ligaments are readjusted to achieve the best possible knee function.

At the completion of the surgery a drainage tube will be inserted to drain excess fluid from the new joint. The surgeon then closes the layers of tissue and the skin with stitches and a dressing is placed around the knee.

Antibiotics are given during and after the operation to prevent the development of infection in the new joint. A blood transfusion may also be required. This will be discussed by the surgeon prior to surgery.
 
A knee prosthesis
 
 Total knee joint replacement 1

Recovery

After surgery your surgeon and a physiotherapist will work together to set recovery and movement guidelines. Initially these include passive exercises, before progressing to gentle knee bending exercises and walking. Ongoing exercises are designed to increase the range of motion of the new joint and to strengthen the surrounding muscles, particularly the thigh muscle (quadricep). Strength in the quadricep will help to keep the knee joint stable, therefore protecting the new joint.

The success of the surgery depends on following the recovery and movement instructions while in hospital and on carrying out the prescribed exercises when at home.

The time spent in hospital can vary from about three to six days. The healthcare team (surgeon, physiotherapist and nurses) will make an ongoing assessment of recovery and will recommend when going home is appropriate. A part of the healthcare team’s assessment will be to discuss if special equipment needs to be installed to assist at home or if home help needs to be arranged.

Crutches will need to be used for up to six weeks after the operation. By six weeks, the majority of people should be able to return to a range of normal activities, including driving.  

Risks of surgery

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

  • The legs may not be the same length after the operation
  • Nerves may 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.

Follow up

It is usual to see the surgeon two to six weeks after surgery to assess recovery. Long-term follow up may also be recommended in order to monitor the wear of the artificial knee joint. It may be that replacement (revision) of the artificial knee joint is required if it loosens and becomes painful. The average artificial knee joint replacement lasts 10 – 15 years before revision is required.   

References

American Academy of Orthopaedic Surgeons (2011) total Knee Replacement.  Illinois: American Academy of Orthopaedic Surgeons. http://orthoinfo.aaos.org/topic.cfm?topic=A00389
Davidson, T. (2006) Joint Replacement. The Gale Encyclopaedia of Medicine. Third Edition. Jacqueline L. Longe, Editor. Farmington Hills, MI. Thomson Gale.
Everybody (2013) Knee Joint Replacements. Everybody. UMBMedica (NZ) Ltd. www.everybody.co.nz
Palmer, S.H., (2012). Total Knee Arthroplasty. Medscape References: Drugs, Diseases & Procedures. WebMD, LLC. http://emedicine.medscape.com/article/1250275
 
Last Reviewed – 26 April 2013 
 
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