Inexplicable bruises on the legs may be caused by accidental bumps and bruises, or they may be caused by thrombocytopenia, coagulation disorders and other factors. 1. Knock: patients are not careless knock, but because of the low pain caused by it, patients do not realize that there may be inexplicable bruises on the legs. 2. Thrombocytopenia: Thrombocytopenia can affect the aggregation of platelets, and the patient’s hemostatic function decreases, showing inexplicable bruises on the skin. 3. Coagulation dysfunction: when coagulation factors are reduced, coagulation dysfunction is manifested in skin bruises, spots and other symptoms. 4. Increased vascular fragility: when vascular fragility increases in old age, it is easy to bleed after minor trauma, and the phenomenon of bruising occurs. When there are inexplicable bruises on the legs continue to be unrelieved or aggravated, you should consult a doctor in a timely manner, a comprehensive examination, a clear cause of the disease, and then active treatment.