I have visible blue veins on the back of my knees and some on my upper thighs. I want to know if that is normal? I am 16 (Photo)

When I turned 16 I started to notice these changes in my legs. Before I have never had this problem. I am really worried about this since I am still so young to be showing sighs of varicose veins etc Is it normal to have such visible veins or does it point to something else. If so do you think that at my age I should be going for a sclerotherapy treatment to stop the veins from getting worse?