Total knee replacement

With total knee replacement surgery, the damaged parts of your knee that need repair will be removed and replaced with artificial parts called prostheses. During surgery an implant, specially selected to match your needs, will be affixed to the underlying bones.

Implants

For some patients, an acrylic cement called polymethylmetrate (PMMA) will be used for fixing the prosthesis in place. It is a strong material, which sets within fifteen minutes after it is mixed and is well tolerated by the body. Before setting, the cement is pressure injected and the implants are positioned. As the bond is strong, most patients are able to bear weight on the leg that was operated on within several days after surgery.

For other patients, the implants can be affixed to the bones without cement. Special surgical instruments are used to prepare the bones so as to enable an exact fit. To supplement this joining, supportive screws or pegs are often used. If an implant is coated with metallic beads to form a porous under surface, and is placed very close to living bone, tissue can grow into the pores, further locking the implant in place.

Preparing for surgery

  • The evening before surgery
  • Do not eat or drink for eight hours before your operation.
  • Before bedtime or early in the morning, shower and scrub the leg that will be operated on with the special soap provided.
  • Intravenous (IV) therapy will either be started the night before or the morning of surgery.
  • You may be given a sedative to help you sleep.
  • Anti-embolism stockings may be provided to promote circulation to the legs. A sequential compression device may also be used for the same purpose.
  • You will be instructed in breathing exercises that will help reduce chest congestion.
  • The morning of surgery
  • The nursing staff will wake you to take your temperature, pulse, respiration and blood pressure.
  • You may brush your teeth and rinse your mouth, but do not swallow any water.
  • A hospital gown and theatre pants will be provided.
  • An elastic stocking may be applied to the leg that will not be operated on.
  • Going to surgery
  • You will be asked to empty your bladder.
  • Remove all jewellery, dentures, contact lenses and nail polish.
  • Rings not removed will be taped.
  • An orderly will take you on a cart to the pre-operative waiting area.
  • The leg that will be operated on will be scrubbed and shaved in preparation for surgery - this usually takes place in the theatre.
  • The anaesthesiologist will discuss the type of anaesthesia to be used.
  • You will be taken into the operating room.

What to expect after surgery

  • Following surgery you will be moved to the recovery room. As soon as your blood pressure, pulse and respiration are stable, you will be moved to the orthopaedic ward or the general high care ward.

The first days

  • Your blood pressure and pulse will be taken frequently during the first 24 hours following surgery. The nursing staff will check the bandage on your leg, and the colour, warmth, movement, and sensation of your leg and foot. Report any pain, numbness or tingling in your leg, foot or heel.
  • For the first couple of days after surgery, you will be given fluids intravenously. Once you can tolerate liquids, your diet will be increased accordingly. If an antibiotic is prescribed as a preventive measure against infection, it may be given intravenously.
  • One or two plastic suction tubes may be used to draw excess fluid from the area around your incision. The tubes are usually removed within 24 to 48 hours when the drainage decreases.
  • A moistened oxygen mask may be used to soothe your throat and loosen secretions in your lungs. This mask can be removed for short periods of time.
  • The trapeze attached to your bed frame will assist you in moving more easily and the side rails of your bed may be raised for your safety. Inform the nursing staff if you experience pain or discomfort, as your operated leg may be swollen.
  • Ice packs may be placed on your knee for 24 hours.

CPM machine

Your leg may be positioned in a continuous passive motion (CPM) machine after surgery. Keep the centre of your kneecap at the bend of the CPM machine and do not adjust the machine yourself. While you are in bed, this machine will continuously bend and straighten your leg. The CPM machine keeps your joint from becoming stiff and speeds up recovery.

Basic guidelines and instructions

  • You will be told how far you can bend your knee.
  • Avoid movements such as kneeling, jumping or strenuous exercises that could twist the knee or cause pain.
  • Put only the amount of weight on your leg as instructed by your physician or physiotherapist.
  • Walk as often as directed by your surgeon.

Pain

Before you leave the hospital, your surgeon will prescribe pain-relieving medication. While some discomfort is normal, you should contact your surgeon if you experience increased discomfort or pain.

Warning signs

Keep an eye open for changes around your incision and contact your surgeon if you develop any of the following symptoms:

  • drainage and/or foul odour from the incision;
  • fever/temperature above 38°C for two days; or
  • pain, redness or swelling.

Remember

Before undergoing any of the following procedures, you will need to take antibiotics to help protect the replaced joint against possible infection:

  • Cystoscopy, colonoscopy, proctoscopy.
  • Dental work, including teeth cleaning.
  • Surgery of any kind.
  • Urinary catheterisation.

If you experience an infection in any part of your body, contact your physician.

Note: A prosthetic device may set off the alarm at airport security checkpoints. Your surgeon may provide you with a special airline card to identify you as a person with a prosthesis.

Results

Results of total knee replacement surgery are generally excellent. Most patients are pain-free and are able to bend their knees from 90° to 100°, resuming daily activities without restriction.

However, it is important to remember that the replaced knee is artificial and there may be occasional discomfort in the area, including some numbness in the skin around the surgical scar.