Total Knee Replacement (TKR)
Other popular names
X-ray of inserted implant
Who does it affect?
Generally older people suffering from Arthritic conditions.
Why is it recommended?
Types of Knee Replacement
Depending on the distribution of areas of cartilage loss within the knee the treatment could be of a total knee replacement, as shown in this picture:
Or it could be of a partial knee replacement, as shown in this picture:
Total Knee replacements will predictably reduce pain because the areas of bony contact due to cartilage loss are obliterated by metal and plastic. However, range of motion after knee replacement is less predictable. The biggest predictor of range of motion after knee replacement is the amount of range of motion in the knee before the operation. Effectively, if you start with a stiff painful knee you should end up with a painless knee with a similar range of motion.
A total knee replacement is an effective way of relieving the pain of an arthritic knee. The replacement is actually a resurfacing of the worn out joint surfaces with artificial surfaces comprising a metal shell coating the ends of the femur and tibia with a high density polyethylene bearing in between. By removing the worn out joint surfaces of bone the source of the pain is removed.
Some patients develop a deformity / bend as a result of their arthritis. Any such deformity can be corrected as part of the knee replacement operation.
Modern knee replacements have been evolving over the last 30 to 40 years and are now very effective at relieving pain and improving function and as long-lasting as hip replacements.
The symptoms and conditions of arthritis are complex. The more commonly associated, wear and tear, osteoarthritis is a degenerative condition, starting from gonarthrosis and progressing through a number of stages to acute arthritis. Your consultant will, through examination, determine the extent of your arthritis and discuss options for treatment available to you.
Arthritis can be diagnosed from plain x-rays. However, on occasions it may be necessary to obtain detailed information on the knee prior to surgery and therefore you may be asked to attend for an MRI or CT scan.
Arthritis is progressive and therefore lifestyle changes, for example to avoid impact exercise will elongate the time before a total knee replacement is necessary.
Physiotherapy can give increased joint movement.
Eventually it is likely the pain will become unbearable or quality of life will be such that the only option is to have a knee replacement.
The operation is normally performed under a spinal anaesthetic as this is generally safer and provides excellent post-operative pain relief. Some patients are worried about being awake; however the level of sedation can be varied such that patients can be as awake or asleep as they wish.
The operation involves an incision over the front of the knee. The patella (Kneecap) and muscles attached to it are moved out of the way to expose the joint surfaces. The worn out bearing surfaces of the knee are resurfaced with metal implants and a polyethylene lining is inserted to separate the 2 metal components and provide a low friction bearing surface.
As little bone as possible is removed to allow an implant that closely matches the size and shape of the patient’s bones to fit accurately. If the knee has become deformed as arthritis has developed then the bones are cut in a way to correct this deformity, making the knee straight again.
The skin is normally closed with staples as these allow full flexion of the knee with minimum risk of the wound opening up. The knee is wrapped in a soft padded bandage for comfort and to minimise swelling. This is removed the day after surgery but the wound is kept covered with a sterile dressing until it is completely dry - normally one to three days following surgery.
The aim is to mobilise patients as soon as possible after surgery - on the same day or the next day as this helps speed recovery.
Most patients remain in hospital for up to three or four days but there is no fixed limit and patients can go home as soon as they can walk safely with elbow crutches and manage whatever tasks they need to perform at home.
Physiotherapy is an integral part of the recovery process and we have physiotherapists who are specifically trained in the rehabilitation of knee replacement patients. They will guide you through the recovery process and assess that you are safe for discharge.
Recovering from a knee replacement is hard work in the first few weeks. The knee will feel stiff and sore. This is normal and nothing to worry about and it is important to recognise this and the need to get the knee bending and straightening despite the discomfort.
Patients should aim to increase the range of movement they can achieve on a daily basis and that the only way to increase the range of movement is to push the knee in to the uncomfortable zone as in general whatever movement is achieved in the first few weeks is kept for life and it is extremely difficult to increase the range of movement after his time.
Most patients do not require out-patient physiotherapy but for patients who are finding the recovery process more difficult then further physiotherapy can be of great assistance and will be arranged if necessary.
Key rehabilitation points:
- Remember that walking will come back naturally and does not need to be pushed.
- The range of movement will not and this needs to be worked at.
- Patients who try and do too much walking in the weeks after a knee replacement tend to find that this irritates the knee and it becomes more swollen - this swelling can then restrict the range of movement of the knee in the vital few weeks after surgery when the window of opportunity to regain range of movement is still open.
- 3 to 4 days in hospital
- most patients are able to drive 3 to 6 weeks after surgery and discard their elbow crutches during this period.
- most patients feel better than they did prior to surgery within 6 weeks
- It takes a year to get the best out of a knee replacement
Return to normal routine
Bathing and showering
The wounds should be kept clean and dry until the wound has sealed. Showering is fine and the waterproof dressings can be changed afterwards. Bathing is best avoided until the wounds are sealed, typically 10 days after surgery.
In summary, whilst the wounds are wet - keep them dry and when the wounds are dry, you can get them wet!
Surgery is followed by a prolonged course of physiotherapy. This requires a commitment to undertake this rehabilitation in order to achieve the best possible result (at least half an hour per day for 6 months). It is vitally important to stay within the post-operative activity restrictions and physiotherapy guidelines to avoid damaging stretching your replacement knee.
Return to work
The timing of your return to work depends on the type of work and your access, however, the following is a general guide:
- Desk work: as soon as pain allows and you can travel easily to and from work (2 weeks)
- Light duties: if the job allows partial use of crutches or limited walking (2-5 weeks). If the job involves standing for prolonged walking, bending, lifting, stairs but no squatting (7-8 weeks)
- Heavy duties: full squatting, heavy lifting, digging, in and out of heavy machinery, ladder work etc (3-4 months)
When you can walk without crutches or a limp and be in control of your vehicle (about 3-6 weeks).
The risks of knee replacement are very similar to those of hip replacement, namely blood clots in the leg and infections around the time of surgery and in the long-term if the knee replacement has been successful for a long time but then becomes painful this is due to either a wearing of the polyethylene insert or loosening of the components from the bone and this can be associated with bone loss.
A knee replacement is successful in relieving all or most or the pain from an arthritic knee in about 90% of cases.
This means that 10% of patients have some pain although most of these feel better off than they did before.
Overall more than 90% of patients are happy with the result of their knee replacement.
A small percentage of patients sustain a complication that can potentially leave them worse off. In general the level of this risk is approximately 2%.
The aim is to provide each patient with a knee replacement to last their life. Statistics suggest that 90% of knee replacements are still working well ten years down the line. However they are mechanical devices and will therefore wear out.
The length of time a knee replacement will last in any one individual is very difficult to predict but a good analogy is that of asking how long a new car will last and of course this depends on how far you go and how well you drive it!