Which point lies between the medial malleolus and the Achilles tendon?

The correct answer is K-3, which is known as Taixi (Great Stream). This point is located in the depression between the medial malleolus and the Achilles tendon on the inside of the ankle. Its anatomical position is significant in Chinese medicine, as it corresponds to the Kidney meridian, which is often associated with foundational energy and essence in the body.

K-3 is used for a variety of conditions including issues related to the Kidney Qi, Yang, and Yin, as well as for strengthening the lower back and reducing symptoms such as fatigue and tinnitus. The precise location of K-3 makes it easily accessible for needling during acupuncture treatments.

The other points listed do not occupy this exact location. K-5 is found more anteriorly and superiorly relative to the medial malleolus, BL-64 is located more on the lateral side of the foot and is not in the vicinity of the medial malleolus or Achilles tendon, and BL-63 is situated in a different area as well, thus not aligning with the specified location in the question.