There are two types of thigh capillary purple, pathological and physiological, and there are various reasons, mainly as follows. 1, thin body, thin and fair skin, less subcutaneous fat, capillaries are naturally more superficial, so they appear on the skin surface, which is a normal physiological phenomenon. 2, capillary dilation, the patient has no obvious capillaries in the legs before, and suddenly more capillaries appear, due to capillary dilation and 3, vascular blockage, capillary blood flow is slow or even unable to flow, resulting in local capillary dilation, tortuous, purple, such as diabetic vasculopathy. 4, disease precursors, such as varicose veins in the lower extremities, saphenous varicose veins can have purple capillaries in the early stage. 5, local soft tissue injury, capillary rupture bleeding, resulting in part of the capillary purple. 6.Hematological diseases, such as purpura, hemophilia, etc.