Huanjian San is a traditional Chinese medicine formula that can be used externally to treat old injuries to the tendons, but the exact effect varies from person to person. It is made of papaya, Boswellia serrata, red peony, Angelica sinensis and Zijinzhuang, etc., which are ground into powder according to a certain dosage ratio. It can relieve tendon pain, activate blood circulation and remove blood stasis. External application of Huajin San is mainly used for the treatment of old injuries of tendons. Generally speaking, the way to use Huanjian San is to mix it with appropriate amount of vinegar and then apply it externally on the injured area. The adverse effects and contraindications of Huanjian San are not known. If you need to use Huanjian San, it must be used under professional medical supervision.