What are common causes of random bruising and leg pain?

Aging: Easy bruising is common with age. Although most bruises are harmless and go away without treatment, easy bruising can sometimes be a sign of a more serious problem. Aging capillaries. Thinning skin. Blood-thinning drugs. Topical and systemic corticosteroids. Blood-clotting problem or a blood disease. Domestic violence or abuse. Consult your doctor if you have unusually large or painful bruises.