Knee Replacement

Do I have to be 60 years before I have a knee replacement? How about body weight?

There is no specific age limit to have a knee replacement. Obviously the later you have one, the better. There is generally no harm in delaying your operation and this would not make surgery any more difficult. High body mass index poses problems during anaesthesia and there are higher postoperative risks.

Are there different types of knee replacements?

The two main types are partial replacement and total knee replacement. Each of these has options of bearings like fixed and mobile bearing surfaces. Your knee replacement design would depend on your clinical needs, age and surgeon experience.

What constitutes a total knee replacement?

The commonest form of knee replacement is a Total Knee replacement. The damaged end of the femur is reshaped to fit a curved metal prosthesis. The damaged tibia surface is carefully cut flat to accept a metal tray. A high-grade plastic spacer is placed between the two metal components that reduce friction between the two surfaces. The damaged surface of the knee cap (patella) may be replaced by a plastic button but is done selectively by most surgeons.

What is a Half knee Replacement?

If the arthritis is localised to one half of the knee, then a partial or half knee replacement can be performed. The aim is to save one’s own normal part of the knee thereby retaining more of the patient’s bone and ligaments. They can be performed through a smaller muscle cut (minimal invasive); the postoperative recovery can be quicker and the functional improvement can be superior to total knee replacements.

What happens while I wait for surgery?

It takes physical and mental preparation to go through a big operation like a knee replacement. It is normal to attend a preassessment clinic where you would have blood tests, ECG and general medical assessment to make you ready for your operation. You would be given leaflets and further information about your operation and some centres have a knee preoperative school run by physiotherapists and occupational therapists. The aim is to give you adequate information and understand your needs postoperatively. You may also be requested to complete knee outcome scoring sheets that help assess your progress with your operation.

Do I take my normal tablets before I come for surgery?

Yes, you should be taking your tablets unless advised differently. Please remind the preassessment team and your surgeon if you are on any blood thinning tablets like Aspirin, Clopidogrel (Plavix) or Warfarin as these may have to be stopped 5-7 days before surgery. Similarly certain new anti-rheumatoid arthritis medication may have to be stopped before surgery.

What is the normal hospital stay and what should I expect when I arrive in Hospital?

Average hospital stay is 3-5 days for TKR and 2-3 days for half knee replacements. This may vary between hospitals. Your surgeon and physiotherapist would see you on the morning of your surgery and this gives you another opportunity to ask any questions. You would have a mark on your leg to identify the knee needing the operation and be asked to sign a consent form. You may be surprised to see the amount of paperwork but these are for patient safety. The anaesthetist would speak to you about anaesthesia and postoperative pain relief using any special techniques like nerve blocks.

What would happen after surgery?

Your surgery would take 60-90 minutes. You would then be transferred to a recovery ward until your anaesthetic wears away. Please don’t be surprised to feel your leg numb as this may be due to spinal anaesthesia or nerve blocks. They help controlling your pain. You are likely to have a bulky bandage and may have a tube coming out of your knee as a drain. The blood that is collected in the drain may be transfused back in to your system. This tube is removed the morning after your surgery. The physiotherapist would give you an early exercise regime. You are likely to start sitting in a chair and walk with a frame the day after your surgery. Subsequently you would progress with crutches and sticks including walking up stairs.

How should I protect my wound?

After the first few days your wound may be left exposed. You are allowed to take a shower as long as there are no wound problems. Blot the scar dry after the shower. Your wound may be closed using skin clips and these would require removal by your GP surgery or community nurse at 14 days. Donot take a bath or swim until the wound is well healed- generally atleast 4 weeks. It helps to massage the scar with an emollient cream to reduce scar sensitivity.

What should I anticipate with my new knee?

Numbness around the scar is common. Most patients regain preoperative knee movements. Expect to regain a straight knee and knee bend to enable sit in a normal chair. Knee replacements can click- this is due to metal articulating with plastic is not due to complications. Kneeling can be uncomfortable and needs practice but is not harmful. Swelling can persist for a few months.

Dos and Don’ts

You are allowed to do a lot of walking. Don’t overdo it if there is swelling. You can get back to hill walking, doubles tennis, exercise bike, Golf and Swimming. Breast-stroke can pose certain problems with both hips and knees and is best avoided. Kneeling is not contraindicated but may need practice. Do not do any impact running or impact sports.

When can I drive after a knee replacement?

Minimum 6-8 weeks after surgery. You would need to be able to get in and out of your car seat comfortably and be able to do an emergency stop. Make sure you have come off any narcotic pain killers. Please inform your insurer when you recommence driving.

What about travel?

You are allowed to take short distance air travel after 3 months. Long-distance flight are best avoided for 6 months. Your new knee may activate metal detectors required for security in airports.

Minimal Invasive surgery. What is it?

A smaller cut is made protecting the quadriceps (thigh) muscle whilst doing the knee replacement. There is no long-term benefit in a minimal invasive technique but short term recovery can be quicker.

What about computer assisted knee replacement?

You would have a Xray of your knee after the operation. You are likely to have an appointment to see your surgeon about 6 weeks after surgery and if progressing well a further review 1year with Xrays. The British Orthopaedic Association recommend that the knee replacements should have a check xray at 5 years and 10 years. Individual hospitals may have limitations on such follow-ups. Remember to see your doctor if there is any persistent pain or new onset swelling.

You should see your doctor urgently if you:
  • Have pain, swelling or tenderness in the joint which is getting worse,
  • Develop a high temperature,
  • See fluid, pus or blood coming from the incisions, or
  • Develop numbness or tingling near to the joint

Contact your hospital ward nurse or your physiotherapist who would liaise with your Surgeon. If it is at late hours in the night, you may have to attend the emergency department and see the on call Orthopaedic Doctor who would assess your knee and speak to your surgeon.