Had post op dvt, now gone told to wear surgical stockings for 2 years , do they mean 2years after it cleared or from beginning .

From the diagnosis: The stockings are meant to reduce congestion and swelling. If there is not swelling during the usual upright day then one may not need them. Follow up ultrasound may be useful in making a recommendation.

Probably from beginn: They likely meant from the beginning of treatment. The real answer is that once you have had one dvt, especially a bad one, you are at increased risk for another one for the rest of your life. It is a good idea for you to wear some form of support stockings forever. This doesn't mean the high compression ones but you should wear some form of knee high stockings to prevent future dvt.

Time to wear changes: A post op DVT is not the same as a DVT without a specific cause. The reason for the stockings is to compress the veins to increase the venous return and decrease any swelling. I rely on post DVT ultrasounds to determine the duration of treatment with compression and type of anticoagulation. The location of the dvt(upper or lower leg) also influences further treatment.