Total Knee Replacement

Total Knee Replacement

Why is a Knee Replacement Performed?

Approximately 80,000 knee replacements are performed annually in the UK and these numbers are increasing each year. The commonest reason to perform a TKR is for osteoarthritis of the knee where the patient’s symptoms are now severe and interfering with quality of life (pain and disability).

X-Ray showing knee osteoarthritis (OA)

What does the procedure involve ?

Knee replacement involves a 3-day stay in hospital. You are admitted to hospital on the day of surgery (you will have had a pre-assessment within 2 weeks for blood tests and a medical examination). The operation is usually performed with a combination of spinal anaesthetic (legs numb from the waist down) and sedation (made to feel sleepy). The operation itself takes approximately 1 hour and you start walking when the spinal anaesthetic has worn off (usually the next day). The operation involves placing resurfacing the femur and tibia and placing implants with a plastic spacer between them.

X-ray showing right total knee replacement

The Aim of Surgery

  • A successful knee replacement will achieve the following;
  • Relief of pain
  • Increased level of activity (walking, leisure activities)
  • Good range of movement allowing full extension and a good amount of bending in the knee (0-115 degrees)
  • Last a long period of time (no early loosening requiring revision surgery)
  • No other complications (e.g. infection, nerve injury)

The knee joint acts as a hinge between the bones of the leg and is effectively two joints. The major joint is between the thigh bone of the upper leg (femur) and the shin bone of the lower leg (tibia). The smaller joint is between the knee cap (patella) and the upper leg (femur).
A smooth, tough tissue called articular cartilage covers the ends of the bones, allowing them to slide smoothly over each other. The synovial membrane that covers the other surfaces of the knee joint produces synovial fluid, which lubricates the joint, reducing friction. 
If the articular cartilage becomes damaged or worn, the ends of the bones rub or grind together, causing pain and difficulty moving the knee joint.

 

Knee Osteoarthritis

Replacing the damaged knee joint with an artificial one can help reduce pain and increase mobility.

What Does the Procedure Involve ?

Total knee replacement comprises resurfacing the bones of the tibia, femur and patella with a metal implant and then placing a high-grade plastic spacer to create a gliding surface.

Knee replacement involves a 3-day stay in hospital. You are admitted to hospital on the day of surgery (you will have had a pre-assessment within 2 weeks for blood tests and a medical examination). The operation is usually performed with a combination of spinal anaesthetic (legs numb from the waist down) and sedation (made to feel sleepy). The operation itself takes approximately 1 hour and you start walking when the spinal anaesthetic has worn off (usually the next day). The operation involves placing resurfacing the femur and tibia and placing implants with a plastic spacer between them.

tkr

Recovery

Physiotherapy starts on the first day after the operation. You will get up and be able to put all your weight on the operated leg (on day one you will use a Zimmer frame for balance). You will have regular physiotherapy whilst in hospital and will be discharged once you are safely using crutches, and are able to walk up and down stairs.

Physiotherapy will continue as an out-patient and you will b discharged once your physiotherapist is happy with your progress. Patients can use crutches for 4-6 weeks afterwards, I recommend using them as long as you need them. You can drive once you are safely off the crutches.

Full recovery is around 3-6 months.

Complications

Knee Replacement is a safe operation that dramatically improves the quality of one’s life. The are some complications;

  • Infection – the overall risk is around 1%. Antibiotics cannot penetrate an artificial material so the worst-case scenario is that the implant will need to be removed if infected.
  • Clots – Deep Vein Thrombosis and Pulmonary Embolism may occur in 2-3% of patients. All patients are placed on anticoagulants (blood-thinners) for 15 days after surgery to minimise the risk.
  • Damage to nerves or blood vessels – This is very rare (less than 1%) and may result in a foot drop if the common peroneal nerve is damaged.
  • Bleeding – Excessive bleeding may occur at the time if surgery and this may require a blood transfusion. Sometimes there can be bleeding after surgery (due to the blood thinners) and this can cause swelling around the knee.
  • Loosening – Knee replacements do not last forever. Rough estimates of around 15 years are quoted, the newer implants and bearing surfaces should last longer, although long-term data is required. One of the best guides is to ask your surgeon the ODEP rating of the implant. Detailed information and implant survivorship can be given using this rating.
  • Ongoing pain – sometimes there can be on-going pain following a knee replacement. This may be due to structures around the knee, e.g. the muscles, or referred pain from the hip or spine.
  • Stiffness – sometimes a knee replacement remains stiff after surgery and there can be a loss of full straightening (extension) and bending (flexion).

 

Which Implant is best ?

Your surgeon will decide whether you are suitable for a partial or total knee replacement. All total knee replacements have an ODEP rating which tracks the survival of a particular type of implant. I use a 10A* rated implant for indicating that 95% of these implants survive at least 10 years. The implant I choose is the Genesis II system and this has the added advantage of alternate low wear bearing surfaces for younger patients (Oxynium).

Components that make up a total knee replacement.

Posted in Knee Surgery.