Purple bruises in the bend of the leg can be treated with hot compresses or medication. However, it is necessary to clarify the etiology of the bruise, whether it is related to trauma, thrombocytopenic disease and so on, so as not to delay the condition. 1. Trauma: when playing or working, not paying attention to the bend of the leg by the impact, subcutaneous capillary rupture bleeding, not timely treatment, blood pooling in the subcutaneous. Hot compresses can be used to promote local blood circulation and the absorption of hematoma. 2 Thrombocytopenia (1) Idiopathic thrombocytopenic purpura: Reduced platelet count or platelet dysfunction, leading to coagulation dysfunction. It may lead to bruising at the bend of the leg even without trauma. You should consult the doctor in time, check the platelets, coagulation function and other related tests, apply glucocorticoids and other drugs under the doctor’s guidance, and need to transfuse platelets and so on if necessary. (2) Acute leukemia: It can also lead to thrombocytopenia and subcutaneous bleeding. When there is severe bleeding, it is necessary to apply drugs such as glucocorticoid and platelet transfusion under doctor’s supervision. Purple bruise at the bend of the leg may also be hemophilia, etc. If the above symptoms occur, you should go to the regular hospital to find out the cause of the disease and get timely treatment according to the cause.