The purpose of this study is to determine whether daily use of a lower limb venous-return assist device, "Venowave', improves leg symptoms, ability to perform activities of daily living, and quality of life in subjects with severe PTS.

Eligible consenting patients will be randomly allocated to receive either the veno-device (active or placebo for 8 weeks and crossed over for a further 8 weeks (active or placebo) following a 4 week 'wash out' period.( A randomized controlled 'crossover' study}

Inclusion Criteria:

• Past History of objectively documented deep vein thrombosis
• Daily leg swelling with discomfort (i.e. report at least one of the following symptoms: heavy legs, aching legs and/or throbbing) for a minimum of 6 months
• Over 18 years of age (and of either gender).
• Villalta score of greater than 14(i.e.severe post phlebitic syndrome)

Exclusion Criteria:

• Episode of objectively documented deep vein thrombosis occurred less than 6 months before recruitment
• Subjects report that their symptoms have been unstable (worsening, improving or variable over the previous month).
• Active venous ulceration
• Baseline leg circumference greater than 50 cm (cuff will not fit subject)
• Symptomatic peripheral arterial disease Peripheral neuropathy