If your ankle twists outward, it's a high ankle sprain. Doesn't say how severe it is, though.
All true. The key to severity is not so much about how the ankle turned, but how much torque was put on his lower leg. Rolling the ankle inward (foot outward) and rotating the lower leg at the same time puts pressure on the ligaments holding the 2 leg bones together.
As per the picture above, Gronk definitely suffered an eversion which likely tore the medial ligaments connecting his leg bone to his ankle/foot. Again, don't know how severe this tearing was but it is pretty much the same as tearing lateral ligaments on the outside of the ankle on a "normal" sprain.
The high ankle sprain results from how much his lower leg rotated at the same time. After watching the replay (available on nfl.com), it did look like there was some rotation involved...so I would say there is a good possibility that the ligaments holding the tibia/fibula together were stressed, making a high ankle sprain diagnosis accurate. However, there didn't seem to be much rotation and the ankle released pretty quickly...so that rotational stress may have been pretty minimal.
Based on observational evidence post-injury, I would say the medial sprain was reasonably severe, though not close to a complete tear. As for the high ankle sprain, it looks like it might be relatively minor. If true, that would mean that Gronk would have a hard time cutting (particularly to his left) but shouldn't be in too much pain when digging in to block or in straight line running movements or jumping. If the medial sprain wasn't as severe as it looked or if he has inhuman healing capabilities, he may be close to 100% by Sunday.
