Brief Answer:
likely venous stasis but several other possibilities can be there..

Detailed Answer:
Hello XXXX, Welcome to HCM,

I've gone through your query and understand your concern,

Now from your description, the first possibility is of a venous stasis, which is accumulation of blood in certain dependent parts of your body (based on your posture, which in this case is prolonged standing or sitting), somewhat the effect of gravitation force is also responsible for this..

The other possibilities are much less significant, so i'm not going in those details..

The main reason for this is slowing of blood flow inside the venous system of the body due to several factors(increasing age, gradual increase of the viscosity of the blood, gradual hardening of the walls of the veins and several others)..

However, not everybody develops this and symptoms and severity varies from person to person..

Please note the it is a risk factor for developing blood clots and even Deep Vein Thrombosis in the venous system, so you should schedule an appointment with a Cardiologist to get yourself physically examined and some relevant investigations as per the findings (Color doppler study of the venous system, coagulation profile etc.).

Please let me know if there's any further queries, i'll be glad to clarify..

Take Care
Kind Regards

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