This is a complication that most people are warned about when signing up for knee surgery.

It is not that it is particularly common, but it can be pretty serious if it happens.

This video is explains what you can do about it.




You have done a good job getting to the end of the 5-Day Challenge. The challenge was all about ordinary practical things related to getting ready for surgery. 

Of course, the real job of rehabilitation only just now begins. This will be the topic of several follow-up challenges, but because you have stuck with this one so diligently, our bonus video is about the very first issue in rehabilitation - maintaining good circulation for those important first few days.

Let’s look at some of the reasons why.

A knee procedure may often last for an hour or two. You will have had food restriction from the night before and fluid restriction for several hours before surgery. This is because it is important to empty the stomach so that you have nothing in it that might ‘whoops up’ and be inhaled when you are not in full control of your reflexes. So you may be a bit dehydrated.

Then you will be put into a flimsy robe and taken to the operating room, where the temperature is set for the comfort of the surgical team, but which takes little consideration for a dehydrated and barely-dressed person lying still on the operating table. So you may become a bit chilled.

Although many patients are unaware of this, you may be given chemicals to totally paralyse your body, while the anaesthetist breathes for you via a machine and a tube that feeds into your lungs. So you will be totally still during this time on the operating table.

The heart is beating oxygenated blood to the extremities but it may not be reaching the legs. Firstly the body chilling may have closed down the peripheral circulation, but also a rubber bandage may have squeezed all the blood from the operated leg and a tourniquet may have been applied at the top of the thigh and pumped up to totally prevent blood reaching your leg. So the tissues will be oxygen deprived.

The tissues under the tourniquet will also be subject to increased pressure, and may be a bit traumatised at a micro level.

Now the operation is performed, and tissues are cut and ‘bleeders’ are cauterised or burned closed. The tourniquet is released, and any remaining bleeders are sealed with the cautery, and the wound is closed and a tight bandage applied.

What do you think all this has done to the normal circulation of the leg?

A critical thing to know is that, although there is oxygenated blood being pumped out by the heart, there is no equivalent pump in the legs to return the blood. The legs rely on a series of valves in the veins that ensure that blood flows in only one direction, and it is the action of the leg muscles - the so-called ‘muscle-pump’ that forces the blood back to the heart.

But your muscles have been kept still, even paralysed for a while, chilled, deprived of oxygen, and circulation is further compromised by cautery, dehydration, peripheral shutdown from being cold. The body does not know that this is all ‘elective’ and it responds as if your body has been assaulted - it tries urgently to heal. Red blood cells become more sticky, expecting to have to clot to close the wound. White cells migrate into the tissues expecting to remove germs. Chemicals cause local irrigation so the tissues swell. So there is a lot going on, and not all of it good.

This is where you have to help your leg. Get up and going as early as you are allowed - to get that muscle pump working again. When confined to bed, use those bed raisers to raise the foot of the bed. Wear your tight stockings to decrease the swelling and increase the pressure in the legs. Take the aspirin or other blood-thinner medication you may have been prescribed. And do foot-pump exercises whenever you can to get some muscle activity even while in bed.

Why does all this matter? Well, these first days are danger days for a blood clot in the leg veins - what we call a ‘thrombosis’ or ‘deep vein thrombosis’. Sometimes this is abbreviated to DVT. A problem is that little clots may shoot up into the heart and get stuck in the tiny vessels of the lungs, decreasing lung efficiency and compromising the heart’s attempts to oxygenate the blood. 

The real danger, though, is of a large clot suddenly breaking free from the vein wall and shooting up into the lungs and blocking the vessels there to such an extent that the lung tissue itself is deprived of oxygen. This is called an embolus. The full medical name is pulmonary embolus or shortened to PE. This can be catastrophic and needs emergency attention, and can even result in sudden death. So the take-home message is that little steps can help to prevent a big catastrophe.



Deep Vein Thrombosis