Hold on, this is related to travel. Bear with me. Having just had total knee replacement surgery I am the proud owner of a pair of anti-embolism stockings designed to prevent blood clots. While none too attractive, I'm thinking they might be useful on trans-atlantic flights to keep my ankles from swelling and to prevent blood clots. Is this a reasonable preventive measure or am I wrong on my theory here?

I just read a Prevention Magazine article that recommended doing that, plus getting up at regular intervals and walking, and drinking plenty of fluids.

The embolism risk comes from the fact that blood tends to pool in the dependent (hanging down) limb, especially when sitting, as the bend at the waist and knee can futher impede the ability of venous blood to return to the heart. Walking does help; a "milking" effect as the leg muscles work and eliminating the pinching off from the sitting position encourages venous circulation.
Anti-embolism stockings are made in such a way that there is greater pressure at the furthest end which gradually lessens toward the top of the stocking - the theory being that the blood will flow to the area of lesser resistance. They can be helful, but be sure that they are properly sized and worn correctly. If too tight - as with too small a size or when worn with bunching up - they can actually make things worse by creating another impediment to circulation.

I joined the DVT (deep vein thrombosis) club two weeks ago, for reasons the experts still can't ascertaine. I'll be seeing my haemotologist this Tuesday the 7th and I plan to ask him his opinion on the efficacy of these stockings. I can post here what the man says, but since every individual case is different, I do hope you'll consult your own specialist. For example, the length of time between your surgery and your planned flight date will be a factor. I do wish you luck.

Good advice Sue. I am a haematologist and suggest the advice given by Marty about walking and fluids (water, NOT alcohol or coffee). Taking a small dose of aspirin is also useful, but you must take medical advice on this because I assume that there is a possibility that, after your surgery, you take warfarin - if you do, then NEVER take aspirin.
Litigation against the airlines is going to open up a huge can of worms, and the traveller may come off worst. Here in the UK, many doctors are testing far too often by asking for a "Thrombophilia Screen". This checks a person's clotting state but also performs tests of a genetic nature which will be on your medical records (called Factor V Leiden mutation, Prothrombin Mutation and MTHFR). These mutations indicate a greater risk to thrombose - therefore resulting in a DVT (or even worse, a pulmonary embolism). If you then add other risk factors such as contraceptive pill, post surgery, smoking, immobilisation or dehydration then the risk of DVT can be 30 times greater. Most people who have this thrombophilia screen in the UK are not told that part of it is genetic and if the airlines demand that people with a greater risk of DVT either indemnify themselves or do not travel, then the can of worms has been opened. In my opinion, it is like having a HIV test without councelling or your consent.
Seek medical advice for all the best ways to avoid thrombosis, but moving around, fluid intake and embolism stockings are excellent for starters.

thanks for all the useful replies. good advice. I'll discuss with my doctor at my next appointment.