The Xi-Cleft acupoints are the sites where qi and blood from the meridians are deeply converged. Each of the twelve meridians and the four extraordinary vessels (Yin heel vessel, yang heel vessel, Yin link vessel and Yang link vessel) has a Xi-Cleft acupoint on the limbs, amounting to sixteen in all. All the Xi-Cleft acupoints, except Liangqiu (ST 34) on the stomach meridian, are all situated below the knees and elbows.
Clinically Xi-Cleft acupoints are used to treat severe acute disorders of the meridians. The Xi-Cleft acupoints on the yin meridians are usually used to treat various blood syndromes and the Xi-Cleft acupoints on the yang meridians are often used to treat various pain syndromes.