A knee replacement involves replacing the worn end of both the thigh bone (femur) and shin bone (tibia). When the entire surface is replaced, this is called a Total Knee Replacement and when only one side of the joint is replaced (i.e half the end of the femur and half the end of the tibia), this is called a Partial or Unicondylar Knee replacement. Partial knee replacements are used when the wear is confined to one side of the knee only and are not an option for all patients. Rarely only the portion of the knee under the kneecap (patella) is involved and in this case, a Patellofemoral replacement is performed. The various pros and cons of each of these options can be discussed with your consultant if relevant.
Most knee replacements involve a strong metal cap (cobalt chrome) on the end of the femur and a metal plate on the tibia and these are separated by a plastic tray (polyethylene).
The most common reason for a knee replacement is pain that has failed to respond to non-operative measures such as simple analgesia & activity modification.
Increasing deformity i.e bowing of the leg, may also be a factor particularly if it is limiting normal day to day activities. Stiffness may play a role but usually in association with pain.
We routinely use a technology known as Computer Navigation when performing a knee replacement. Rather than traditional jigs to guide the bony cuts, special markers fixed to both the thigh and shin bones allow the cuts to be performed extremely accurately. This should ensure that your knee is not only well aligned but also well balanced at the end of the procedure.
Most knee replacements are performed under a spinal anaesthetic, where the legs are numbed from an injection of local anaesthetic into the back. This can be combined with sedation if you prefer not to be aware of the surgery. Occasionally a general anaesthetic is used for various medical reasons, but ultimately this is the decision of the Anaesthetist looking after you and can be discussed with them prior to surgery.
The bulky wool & crepe bandage can be removed 24 hours after surgery. The dressing underneath can remain in place for several days & only if it leaks blood will the nurse change it. As a general rule, the less the wound is interfered with, the better. It is fine to shower but avoid getting too much water directly on the dressings. The paper stitches can remain in place for 2 weeks. At this point, you can shower without the dressing on & the paper stitches will peel off easily when wet.
A scar will run down along the front of the knee, slightly to the inside of the kneecap. This is closed with a dissolvable suture under the skin with additional paper stitches (like pieces of tape) on top. It is normal to have an area of numbness especially on the outer part of the knee but this should diminish over 12 - 18 months. The scar itself is quite red and raised initially and matures over 6 - 12 months when it will be flat and slightly lighter than the surrounding skin.
At the end of the procedure, some local anaesthetic is injected around the knee joint. This will usually ensure minimal pain following the surgery. As the local anaesthetic begins to wear off (usually after 12 - 24 hours), discomfort can return. This can be minimised with a combination of simple analgesia such as paracetamol, an anti-inflammatory & a stronger morphine-like tablet or injection (depending on patient tolerances / allergies). If you are in significant pain, call the nursing staff to help get some more analgesia.
When patients return home, they often forget to continue using ice packs. These when combined with a few minutes elevation can really help reduce pain & swelling. Try to adopt the motto “work hard, rest hard”, by performing your exercises regularly as directed by the physiotherapist but then getting the leg up on a couple of pillows with an icepack. A frozen bag of peas wrapped in a towel works fine.
You will usually be reviewed 4 weeks following surgery. This allows us to ensure that the incisions are healing and check the motion. It is often the best time to have a talk about the procedure and ask any questions regarding returning to normal activities.
Bleeding, infection & clot (deep vein thrombosis) are the most common complications. A clot can travel to your lungs (pulmonary embolism) and this could result in death. Every effort is taken to minimize this risk with injections to thin your blood and stockings/foot pumps to maintain circulation. There is also a risk that you will require a blood transfusion. During surgery, there is a small risk of fracture or damage to the main artery or nerve in the leg. Ongoing pain and stiffness can both occur. In addition, you will notice a patch of numbness over the knee. Finally any implant can loosen with time and may require further surgery in the future.
It must be stressed that recovery from a knee replacement is not easy. Beginning to bend a swollen, bruised leg involves a degree of discomfort and determination. Your physiotherapist will be there to supervise and encourage you & rapidly you will start to notice improvements. Exercises should be performed regularly and diligently as directed by the physiotherapist. It is often useful to take some simple analgesia 30 minutes before your exercises.
Long term, this will be fine but because of the incision, the front of the knee will feel quite numb. Patients often find that it may be up to 12 months after a knee replacement before they can kneel on it.
This is obviously dependent on the nature of the work. Office based workers may be able to return after 6 weeks but for manual workers, 3 months is a more realistic goal. Don’t forget to think about how you normally get to & from work when contemplating returning.
Roughly 6 weeks following surgery is reasonable. If you have an automatic car and it is your left leg, then perhaps you can start earlier. Bear in mind that sitting in a car involves a significant knee bend and anything longer than a few minutes can be very uncomfortable.
🏊🏼 Swimming is not recommended for the first 3 weeks after surgery until the wounds have healed. You can go for short walks 1 - 2 days after surgery & begin to build this up over the next week.
🚴🏻 After 2 weeks, you can begin to use a stationary bike with the seat raised. This can be slowly lowered over the next few weeks as the knee bend improves. It is best to leave a road bike for 3 months after surgery.
You should seek advice if the pain dramatically worsens after discharge. Also call if the knee becomes a lot more swollen or you get a large amount of bleeding. Any symptoms such as calf swelling or tenderness or simply feeling unwell or shortness of breath should also be assessed.
Compiled October 2015
Review date: March 2016
Review date: March 2016