A high ankle sprain refers to tearing of the connective tissue that connects the lower part of the tibia to the fibula. The tibia is the larger of the two bones in the lower leg. Your shin is the front of the tibia.
The fibula is the smaller bone (along the outside of the leg). Syndesmosis is the name of the connecting tissue between these two bones. Another word used to describe high ankle sprains is syndesmotic.
The syndesmosis is actually more than just a single layer of connective tissue between the tibia and fibula. That’s certainly part of it but there are also four strong ligaments involved (anterior inferior tibiofibular ligament, posterior inferior tibiofibular ligament, interosseous ligament, transverse tibiofibular ligament).
With that much ligamentous support, you can imagine the kind of force it takes to tear them. Most of these high ankle sprains occur when the player collides with another player or gets hit with enough speed and force to fracture one or both of the bones and the ligaments. In all cases, the foot is planted on the ground while load is applied above the ankle.
A similar mechanism (pathway to injury) occurs in skiers or skaters who have the foot planted firmly, then twist or torque suddenly. Pressure applied along the top of the rigid boot from the sudden force is enough to tear the stabilizing soft tissues (ligaments and connective tissues) just described.
Without a normal, healthy, intact syndesmosis, the ankle becomes unstable. Of course the athletes who need a stable ankle the most are the very ones who injure this area: ice hockey players, soccer players, and football and rugby players.
Recovery takes time. As the tissues are healing, the skater (or other injured athlete) must be careful not to strain or overstrain the injured area. A carefully controlled and monitored rehab program is usually supervised by a physical therapist. Unless you hear differently, most likely, the skater is off the ice for the rest of the season.