The sudden bruise on the thigh may be pressure purpura, which is a disease caused by capillary rupture and red blood cell exudation under the action of external force, and is usually treated as follows: 1. You need to check the blood routine to see if the platelets are abnormal. Check the coagulation series to see if there is any significant change in the coagulation status. If there are no special changes in the above conditions, it can be temporarily observed, generally about 7 days to completely improve and subside; 2, in ordinary life, patients need to pay attention to avoid trauma, extrusion and destruction, and at the same time can take a certain amount of oral vitamin C capsules or rutin tablets to improve the permeability of blood vessels, and avoid spicy and stimulating food, avoid strenuous exercise.