With time and physical activity small capillary veins can appear on the skin surface, mostly of the lower limbs, due to congestion and lack of strength of the vein system.
In many cases it is a problem related to the superficial vein system, although in some cases it can be an indirect sign of lack of function of the deep venous system.
For this reason, before any aesthetic treatment, your surgeon will ask for a Doppler examination to exclude any major issue with the main venous circulation and treat only the esthetic problem.