The term ‘total knee replacement’ is actually quite confusing for patients, because we don’t actually replace your entire joint. The muscles, major ligaments and tendons around your knee joint are preserved. We don’t remove or replace them. In fact, we need them to continue to work normally after your surgery.
What is a Total Knee Replacement?
All we are really doing is providing you with a new joint surface to walk on. Just like when the rubber on a car tyre wears out, we don’t replace the entire metal rim of the wheel, and the axel, brake pads and everything else. We just replace the worn-out rubber tyre.
A knee replacement is a very similar concept, we are literally putting some more rubber tread back on your worn-out knee joint, so to speak. We are not replacing the whole wheel.
Total Knee Replacement Surgery
Knee replacement surgery takes place through a single incision on the front of your knee joint.
Firstly, we remove just a few millimetres of this diseased, worn out, bone and cartilage from the end of the thigh bone and the top of the shin bone. This does require your surgeon to make some cuts into you bone, but this is done carefully and with precision.
The two surfaces of bone then end up with flat cuts on the bones. This enables us to securely position the prosthesis into your knee.
On the end of the femur, we place a metal cap like this. This effectively becomes the artificial cartilage of the femur. It protects the bone beneath and provides a smooth surface for the joint to glide upon.
We also place a metal prosthesis into the top of the shin bone. Attached to the top of this metal prosthesis there is a very smooth and strong piece of medical-grade plastic. Technically it’s called ‘high molecular weight polyethyelene’ but you can think of it as acting just like the Teflon in your non-stick frypan. This acts like the artificial cartilage of the shin bone, and the thigh bone prosthesis can now smoothly glide over it, with minimal friction.
Most joint replacement surgery occurs with a spinal anaesthetic. But this does not mean you will be awake during the surgery; your anaesthetist will provide some gentle sedation so you will feel drowsy and not remember the procedure. You also have the choice of having a general anaesthetic, where you would be fully asleep. Your anaesthetist will discuss the different options with you, but my recommendation is that you choose spinal anaesthesia.
Total Knee Replacement Recovery Time
Full recovery from a knee replacement may be up to 18 months after surgery. This is how long it could take for your knee to be as ‘good as it will ever be’. In other words, there can still be ongoing improvement in your knee function for up to 18 months after surgery.
Most patients will spend 3-5 nights in hospital after a knee replacement. The high majority of my patients choose to go straight home after their stay. The safest place for most patients to recover from their surgery is in their own home. If you have specific health needs, or just require a little bit more support, you have the option of an extended period of rehabilitation within a hospital.
You are allowed to stand up and walk on your new knee as soon as your pain control and strength allows you to. Most patients will aim to at least sit out of bed, stand and shower the day after their surgery. A physiotherapist will work with you every day in hospital to get you up and moving, and also to provide a basic game plan for your rehabilitation in the weeks after you leave hospital.
In the first 2 weeks after surgery most patients will be in significantly more pain that they were prior to surgery. Your pain will be manageable with the medication and other supports we provide to you. You can expect your knee to be significantly swollen during this time. Most patients will require the use of a frame for the first few days after surgery, and then a walking stick for several weeks after.
Driving a car can usually occur from 4 weeks. Most occupations would require 4 weeks off work completely, but a return to light or office duties could occur from 4-6weeks. I would strongly encourage a transition period of working from home if possible. Your knee will be sore and swollen if you spend long periods of time walking around and on your feet.
Returning to manual duties would be a minimum of 6-8 weeks after surgery, and possibly longer depending on your occupation.
By 8-12 weeks the majority of patients will be 50% recovered and beginning to feel that their knee is feeling better than it was prior to surgery.
By 6 months the majority of patients will be 70-80% recovered, and back into all usual activities. Most patients are not taking any pain medications during this time.
The final 20% of your recovery occurs slowly but gradually from 6 months after surgery, right up until the 18-month mark. During this period of time your body is still very much healing and recovery from the surgery.
As with all surgery, there are some risks with knee replacement. All patients will have some degree of mild, ongoing bleeding and oozing inside the knee for a few days after surgery. This is one of the reasons your knee is swollen.
Scar Tissue Formation
Scar tissue formation after your surgery will limit movement. If we don’t get your knee moving, the scar tissue with set in your knee like concrete and permanent stiffness will result. All knee replacements are initially painful and stiff after surgery, and it does take time to regain this movement. This is one of the reasons that it is important to take regular pain medications after your surgery. Many patients don’t like taking regular pain medications, but if you don’t take them you will be unable to participate in your rehabilitation and get your knee moving.
Blood Vessel Damage
Injury to a major blood vessel is a very rare complication, but if it occurred you may require additional surgery to repair the blood vessel.
Damage to a major nerve is also very rare, but if it did occur you could be left with some permanent weakness.
Infection is thankfully a rare complication, occurring in less than 1% of patients. However, if you do have a deep infection inside your joint it can be challenging to treat. It will require further surgery to wash out the infection, several weeks of antibiotics, and sometimes a number of operations to remove the infected knee prosthesis and replace it with a new one.