Knee replacement is one of the most common types of major surgery in the UK. It’s also considered to be very safe. As the NHS puts it: “Most people who have a knee replacement have no complications. If there are any, they are usually minor and can be treated.”
But of course, like all surgery, knee replacement isn’t totally immune from all risk. You may have heard that one of these is deep vein thrombosis (DVT), a condition that’s often talked about in relation to long-haul flights.
Let’s look at why DVT can affect people who undergo surgery, and what knee replacement patients can do to prevent it.
What is DVT?
Deep vein thrombosis is when the blood thickens and forms a clot inside your body, often in one of the deeper veins in the legs. In the right circumstances, clotting is a good thing – it’s the body’s defence against a continuous bleed when we cut ourselves. But if blood clumps together inside a vein, it can be potentially dangerous – especially if the clot travels up to the lungs (a pulmonary embolism).
Why does surgery increase the risk of DVT?
There are a few reasons why major surgery increases the risk of DVT. Two of the main ones are:
- Lack of movement – lying still for a prolonged period slows the flow of blood around the body, potentially causing it to settle as it passes through the deeper veins
- Tissue trauma – blood can sometimes collect around the tiny particles that are released by the incisions during an operation, or where a vein has been damaged
How can patients avoid getting DVT?
Although good treatments are available for DVT if it occurs, the potential risks attached to the condition mean it’s important to take the right measures to avoid it if possible. In medical-speak, this is known as prophylaxis – treatment that aims to prevent a disease or complication. Some of these treatments will depend on factors like your age, medical history and overall state of health. So your medical team will discuss these with you say they can put a plan in place for your operation.
But, in general terms, these are some of the key approaches:
Aspirin
Best-known as an over-the-counter painkiller, aspirin also has “antiplatelet” properties. This means it helps to prevent blood cells from sticking together. It’s why your medical team may prescribe you a daily dose of aspirin after your knee replacement. The standard recommendation (based on NICE guidelines) is from 75mg to 150mg per day, taken for two weeks after surgery.
Movement
Exercise is about the last thing we feel like doing after an operation. But getting mobile, as early as possible, is important for improving blood flow. Even flexing the toes up and down while you lie in the hospital bed, or moving the ankles in gentle circles, makes a difference. When you go home to continue your recovery, you’ll want to build up the movement as you’re able to.
Water
Dehydration heightens the risk of DVT because it can slow the circulation and lead to thickening of the blood. So it follows that drinking plenty of fluids is very important after a major operation. Bear in mind that not all fluids are created equal: coffee and alcohol have a dehydrating effect, so are best avoided.
Anticoagulants
Anticoagulants are medicines that act on proteins in the blood, essentially making it more difficult for the blood cells to stick together. Common types include warfarin and apixaban. Although anticoagulants are prescribed for some knee replacement patients, however, they aren’t appropriate for everybody because they can lead to more bleeding than normal.
Compression socks
Compression stockings are designed to fit more tightly around your legs than regular socks; some types even have graduated compression, so they get progressively tighter down to the ankles. The idea is that the tightness creates gentle pressure on the legs, which encourages blood flow up through the veins towards the heart.
Compression devices
Using the same principles as compression socks, these are specialist sleeves that fit around the lower legs and automatically tighten / relax at intervals (they’re also known as intermittent pneumatic compression devices, or IPCs). They can be particularly helpful for people who struggle with mobility.
Interested in reading more about this topic? You may find these articles helpful:
DVT (deep vein thrombosis): NHS overview
3 Resources to give you confidence about knee replacements (blog)
