Rabbit Knees and Hockey
The flying knee of Muay Thai gets a lot of attention, but a lesser known technique is the “kao kratai,” or “rabbit knee.” In this technique the fighter knees the opponent in the inner or outer thigh. It can be used in a clinch, but can be launched from a greater distance.
One can see the knee-to-to-the-thigh strike used commonly in hockey. You can see the video here. Admittedly, the hockey strike is delivered while moving on skates at a pretty good clip, but the knee strike can be devastating. A knee-to-thigh strike delivered by Ulf Samuelsson (regarded as one of the dirtiest hockey players ever) ended the career of Bruin star Cam Neely.
In the Tony Jaa movies you can see him counter kicks with knee strikes to the inner thigh.
I hope this reinforces the idea that you can learn from unexpected sources. You can learn from football players, hockey coaches, dancers, cops, fencers, etc.