Castor seed can only cure knee pain caused by carbuncle (a kind of poisonous sores, acute suppurative diseases occurring on the surface of the body, limbs and internal organs), and has no obvious effect on knee pain caused by other reasons. Castor seed is calm, sweet and pungent in taste, can enter the large intestine and lung meridian, both good diarrhea and stagnation, but also can reduce swelling and pull out the poison, can be used for stool dryness, paralysis of the larynx (pharynx red, swollen and painful, or dry, with a sense of foreign body, or pharyngeal itching discomfort and swallowing difficulties), scrofula (mainly refers to the cervical lymph nodes tuberculosis), carbuncle swelling and poison, and so on. Pregnant women and those with weak spleen and stomach, large intestine not solid stool slippery, prohibit this drug; this product is toxic, should not be over-served, long service. However, not all knee pain can be treated with castor beans, such as knee pain caused by bumps and bruises. Castor has a certain degree of toxicity, improper use may be poisonous, patients should not be used indiscriminately, must be guided by a professional Chinese medicine.