Total Knee Replacement
The numbers of total knee replacements (TKR) being performed yearly now exceed total hip replacements. This reflects how common knee arthritis is and how disabling it can be. Osteoarthritis is a degenerative condition which occurs when the joint cartilage covering the femur and the tibia wear away. This damage occurs over time but certain conditions like a previous knee injury or fracture can speed up the process.
Knee osteoarthritis presents with knee pain and stiffness which affects walking distance and activities of daily living. Night pain can be a major issue. Patients often note that their knees seem to appear more “bowed” or “knock-kneed.” This reflects progression of the disease.
The diagnosis is usually made on weightbearing x-rays but early changes can sometimes only be detected by MRI or a knee arthroscopy.
Initial management
Initial measures include activity modification such as avoiding impact activities like running, analgesics like Panadol Osteo (paracetamol) and anti-inflammatories like Nurofen (ibuprofen) or Mobic (meloxicam). Injections can give some medium term improvement in pain and can help delay surgery.
Procedure information
When conservative measures fail, it is then appropriate to consider a TKR. This operation involves replacing the worn joint surfaces and provides the benefit of reducing pain.
As TKR is major surgery, it is important to discuss the benefits and risks of surgery prior to making a decision to go ahead.
Knee replacements are performed using very accurate jigs in theatre but occasionally computer navigation or even patient specific jigs are used.
It is important for the patient to work hard on knee conditioning and range of motion post–operatively. This is extremely important in achieving the optimal result as one of the problems after a knee replacement can be loss of range of motion. Most patients find that it takes 3-6 months to recover fully from a total joint replacement.
Most complications are temporary setbacks. The results of knee replacements are generally considered to be excellent and the strong likelihood is that you will undergo the operation without any problems.
Some complications of total knee replacements include:
- blood clots
- postoperative infection
- loosening of the prosthesis from bone
- knee stiffness – this complication can be avoided by careful observance of post-operative instructions and rehabilitation protocols
- fracture
- residual pain and stiffness can occur
- damage to nerves or blood vessels
- allergy to the prosthesis (rare)
- anaesthetic issues
The experienced and cautious surgical team use special techniques to minimise all the above risks. Adverse events following knee surgery are extremely rare but they cannot be completely eliminated.
What to expect
How long will I be in hospital?
This procedure is a moderately large orthopaedic procedure and usually requires 3-4 days in hospital as well as a further in-patient period of rehabilitation.
When can I walk on the leg?
Patients are encouraged to get up and walk on the leg within 24 hours of your surgery. This may be aided with crutches or a frame; guided by our surgeon and physiotherapist.
Will I have a splint on my knee?
A Zimmer knee splint is sometimes used in the early post operative recovery period to aid in controlling the leg when walking. Your quadriceps muscles may be a little bit weak in the early post operative days requiring support. The knee splint can be discarded as soon as you can hold your leg straight against gravity.
What are the risks of surgery?
This operation, as with any others, requires an anaesthetic which in a fit, healthy young person is relatively straight forward. Specific anaesthetic risks will be discussed with your anaesthetist.
Risk of deep infection following this procedure is about one in 200. This is minimised by antibiotics given in your drip for 24 to 48 hours following your surgery.
A blood clot in the veins of the calf (deep venous thrombosis) is a potential risk but a blood thinning injection (heparin) will be given to you at the time of your operation to thin the blood enough to minimise this risk. If a blood clot should form, break off and go to the lungs, it can be serious and you must report any shortness of breath, coughing up of blood or severe chest pain. These are the signs of a pulmonary embolus.
What happens if I get an infection?
This is a major problem and may require further surgical procedures.
Will there be anybody else involved in my care?
Your surgeon has a strong team involved in managing your operation including a fully qualified consultant anaesthetist, surgical assistant and physician to help manage associated medical issues.
When can I drive?
Following a large procedure like this, a 6 week period will elapse before you are safe to drive. The key to the decision on driving is whether you can safely stop in an emergency situation. You can be guided by sitting in a stationary vehicle sitting in your driveway, imagining an emergency situation and attempting to make the appropriate avoidance procedures. If this is uncomfortable, you will know it is not safe to begin driving at this stage.
What is my prosthesis made from?
The prosthesis is made from a stainless steel metal alloy that is fixed to the bones with bone cement and impregnated with antibiotics to minimise infection risk. A polyethylene (plastic) bearing surface and spacer is attached to the tibial (shin bone) component to allow free movement between the components. The knee cap may need to be replaced when severe arthritis affects the kneecap as well.
Adapted with permission from https://orthoinfo.aaos.org