What is a knee replacement?
When the cartilage lining the knee joint has worn down to the extent that there is severe pain, a replacement knee joint may be the only solution. There are many current designs and manufacturers of knee replacement joints but the basic principle is to remove the joint and fix a new metal-on-plastic bearing onto the femur and tibia bones. We use the PFC Sigma implant, which has well-published excellent results over many years.
Why is it performed?
Pain is by far the main reason for performing a TKR, but you may also be suffering swelling, stiffness and deformity in the joint. If you do not have significant pain, it is probably not appropriate to undergo a TKR, due to the risks involved.
Caution is also advised if you are under 60 yrs old, as having a TKR at a young age will almost certainly mean you will require revision surgery at some stage, when the artificial joint wears out and/or loses its fixation to the bones. The decision to operate is taken jointly, between you and your surgeon.
What does the operation involve?
You will first be “pre-assessed” to ascertain whether you are fit enough to undergo the operation.
The surgery is undertaken with special precautions to avoid infection – a special system of airflow in the operating theatre, prophylactic antibiotics, and sterilisation of all the instruments, implants and surgical area. Precautions are also taken against deep vein thrombosis, such as stockings and blood-thinning injections into your stomach.
The operation is usually done under general anaesthetic with an average 7-day stay in hospital. An incision is made over the front of the knee, through which all the surgery is performed. A tourniquet is used to minimise loss of blood during surgery, but some blood is usually lost into a special drain in the first 24 hours after surgery. Rarely, you may require a blood transfusion post-operatively.
What about pain?
Whilst you are in hospital you will be monitored and the medical staff will give you painkilling infusions, injections or tablets as required and prescribed. When you are at home you may find Paracetamol-based analgesics and/or Ibuprofen useful for controlling any pain. Instructions on management of pain will be given by the nursing staff before you leave the hospital.
How long does recovery take?
You should expect considerable swelling in the knee and lower leg for some time. You will be encouraged to walk with the help of physiotherapists as soon as possible after surgery, usually the second day. Gradually during your inpatient stay, the pain subsides, the movement in the joint improves and your confidence grows. When it is felt that you are “safe” to go home, you will be discharged.
Your wound dressing will be changed and stitches removed (if applicable) at the clinic during your follow up appointment, which is usually 10 days after the operation.
With the guidance of the physiotherapist, you will enter a stepwise period of rehabilitation. The emphasis in the first few weeks is in recovering range of movement. You can expect to need a walking stick or crutch for a few weeks, and patients vary greatly in their speed of recovery. You should also expect swelling for several months, but as long as things are slowly improving, there is no need to worry.
Swimming will be possible once the sutures are removed and the wound has healed satisfactorily. You are advised not to fly after surgery for about 6 weeks. Driving is usually possible after 6 weeks.
What can go wrong?
All operative interventions have an inbuilt risk and complication rate. The risks following TKR include:
- Complications of the anaesthetic procedure.
- Infection (in the wound or the joint replacement itself).
- Excessive bleeding / blood vessel damage.
- Injury to a nerve.
- Deep vein thrombosis (clot in a vein).
- Pulmonary embolus (clot in the lungs).
- Stiffness (inadequate range of movement).
- Residual pain.
- Loosening or wear requiring revision surgery.
The above complications are rare but can occur.
