Final answer:
A high ankle sprain is an injury to the syndesmotic ligaments of the distal tibiofibular joint, a syndesmosis joint that allows for slight movement but is held together by ligaments.
Step-by-step explanation:
A high ankle sprain involves an injury to the syndesmotic ligaments that connect the tibia and fibula above the ankle. This type of joint is known as a syndesmosis, and it is a slightly movable joint held together by ligaments or an interosseous membrane. The sprain occurs when there is a lateral twisting of the leg with the foot planted, leading to over-stretching or tearing of these ligaments, causing pain and instability in the distal tibiofibular joint.