A bruise on the leg is not leukemia in most cases. Because there are three most common causes of bruises on the legs, one is allergic purpura, two is thrombocytopenic purpura, and three is simple purpura. The most common causes of bruises on legs are allergic purpura, thrombocytopenic purpura, and thrombocytopenic purpura, which is caused by the decrease in the number of platelets and the decrease in hemostatic function. Simple purpura is common in women of childbearing age and is related to estrogen concentration. Unexplained purpura appears on the legs and tends to recur. If the purpura on the legs is caused by leukemia, in addition to purpura on the legs, there will be anemia, infection, fever and other symptoms, and the routine blood tests are not normal. So there is no need to worry about bruises on the legs, in most cases it is not leukemia.