Scaling and moving bones? Will it break animations?

[Sloofish]

I have been told by numerous people to never touch, resize, or move any of the bones of the base skeleton if you don't want it to break with animations. I know that can't be true given the sheer diversity out there with proportions. I wanted to know if there's a "safe way" to move bones. For example, these leg bones up? 

[OptimoMaximo]

On 5/28/2019 at 10:08 PM, Sloofish said:

I know that can't be true given the sheer diversity out there with proportions

Those proportions are achieved using the bones scale, that's why this joint attribute is disabled in SL animations. If you do scale the bones on your side, you won't get the same exact result as in your application because the relative location of each bone head and tail in world space would differ from the avatar's, inworld.

For what concerns their position, it's a different matter. That feature is intended to give the option of different shapes other than human, and both the joint roll and posizion play a huge role in how the animation is output and, finally, how it will be played back inworld. Making sure that the bone roll is compliant to SL's default avatar skeleton, animations work just fine BUT there will be some (if not a lot of) discrepancy between your animation design and what you will see inworld. As a general rule, when joint position is involved in the creation of an avatar, the mesh is marked as "use joint position" during upload and animations should only run on rotations.

From your picture, i think you are in need of a better repositioning of your leg bone, which you can do by deleting the armature modifier, perform your fixes, set this pose as new rest pose and attaching a new armature modifier.