Knee Replacement and Deep Vein Thrombosis - What You Need to Know Before Your Operation!

Deep vein thrombosis or DVT is a blood clot that forms on the walls of veins in the extremities, most common in the calf. The risk factors for DVT include: Surgery - particularly orthopaedic surgery to the lower limb Immobility Advanced age Obesity Active cancer Infection Previous DVT Oral contraceptive pill Clotting disorders.

With most people undergoing knee replacement over the age of sixty, they have multiple factors increasing their risk of DVT. The thrombosis itself causes pain and swelling, but the major risk is that the clot will break free and travel via the heart to the lungs where it causes a pulmonary embolism. A Pulmonary embolism (or PE) is where the clot from the legs blocks an important artery in the lung and prevents the exchange of oxygen and carbon dioxide.

A large pulmonary embolism can be immediately fatal so precautions are taken to protect patients from DVT. Clots form when the blood pools in the calf. The lack of blood movement allows it to get 'sticky' and attach to the wall of the vein. Preventative measures aim to keep the blood moving and decrease the 'stickiness' of the blood itself. Compression stockings help the blood return to the heart and prevent pooling. Intermittent pneumatic calf compression can be provided via a pump at the end of a hospital bed that squeezes the legs to maintain blood movement.

Ankle movement also turns the leg muscles on and off creating a pump effect inside the leg. Unless their medical history makes it unsafe, most patients are given a blood thinning medication after their operation to help prevent clots. This is usually what is called a Low Molecular Weight Heparin, and is often administered by injection. It is not given before the operation as it can lead to excessive blood loss.

In the event of a clot being diagnosed in the calf, higher doses of blood thinning drugs are given to break the clot up. Often patients will be required to continue taking blood thinners via tablet form an extended period after the clot or even for life. Your hospital will organize preventative measures and treatment if required, but everyone should remember that moving your ankles up and down does not hurt (even immediately after the operation) and is a very simple thing that can reduce your risk of complications. Remember - there is no such thing as too many ankle movements!