Are lines of bruises on the left leg a sign of anything?  

Some trauma? Bruises are from blood leaking out of capillaries (tiny blood vessels) in the skin. Having bruises means there was trauma to the area. If there was no trauma, the bruises mean either the blood vessels are abnormally fragile and break easily, there are too few platelets to help blood clot, or the blood is "thin" and not clotting fast enough. A doctor's evaluation may be needed to figure things out.
Trauma? Sometimes a bruise at the groin will show spread down the tissue planes all the way to the ankle. Like after an angio or cath or repeat local trauma can give multiple bruises like kicks from an infant. Think back?