Don't move the knee
At a higher level when the inside of the body is stretched out, the outside frames (structure) of the body should start to close. This is in compliance with the principle of "the energy must be released but structure remain intact".
Here are some simple explanations of the structure and energy movements of the knee.
- The whole body power aims at the front kua.
- Energy comes out of dantian and then front kua.
- The energy that comes out of the front kua must only travel in a straight line to the knee.
- It must have the tendency to travel straight past the knee (as indicated by the straight red line with an arrow).
- The white vertical line is an assumed hard wall, blocking the traveling energy from the kua.
- The curved red line with arrow is the resultant energy path.
- This is how energy can pass through the knee to go to the foot.
- In practice, one must ensure that the imagined while wall line is made real and motionless.
- The movement of energy along the red arrow line is made less stable and powerful than the white wall line.
- The production of a fixed spot on the knee and the vertical wall is crucial.
- Any movement on the knee, especially horizontal movement, will disrupt the energy moving to the foot.
Source: https://practicalmethod.com/?p=32387