I wear a 30-40 mm thigh high stocking for a dvt ten inches above knee 4.5 months ago. is thigh high the right length? how long should i wear 30-40?

Post Thrombotic Syn: Within two years of their diagnosis, 27% - 47% of patients with a history of DVT develop post thrombotic syndrome, of which approximately 10% are associated with ulceration. The use of 30-40mm hg calf-high compression stockings for two years after DVT development will help reduce the risk of post thrombotic syndrome.

Varies: Since your clot was in the femoral vein above the knee, thigh high stockings would be appropriate since you want to compress the veins around the clot to increase the venous return in that area. The amount of compression and duration of compression varies. I like to do a follow up ultrasound 6 months after the onset of treatment to reevaluate the clot and then determine continued treatment.