Thromboembolic disease refers to a group of conditions which involve blood clots to the leg or lung, Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE).
These can occur after surgery and happen in around 1 in every 100 procedures. Most DVTs cause calf pain and swelling which may require a period of treatment with blood thinning medications. However one patient in ten with an untreated DVT can develop a severe pulmonary embolism which in the worst cases can be fatal.
If you or a close family member has suffered from Deep Vein Thrombosis or Pulmonary Embolism, you should tell your surgeon and anaesthetist before surgery. You will also have risk assessments at the time of surgery. 
If you are higher risk then you can be prescribed a blood thinning injection to help reduce the risks after surgery.
For more information about Thromboembolic disease please visit:
https://www.nhs.uk/conditions/deep-vein-thrombosis-dvt/complications/