Legs spontaneously roll inward when fully extended

Hi everyone,

I’m experiencing an issue that I have on all of my avatars, both ones that I’ve made as well as ones that I’ve reskinned for others (so other av makers also experience this problem it seems).

My legs spontaneously roll inward when straightened.

Yes, I’ve seen this video: [NEW 2020] VRChat FBT Fixes (Fullbody Avatar Mega-Tutorial) - YouTube

This video was extremely helpful, but it has not at all addressed this issue. I have done everything the video suggests and the problems persist.

What else can I do to prevent the spontaneous rolling inward of bones? Is there some way that I can use bone constraints within unity? Is there some way that I apply the constraints within Blender itself? I know that there is a solution which exists, because I’ve seen it working on certain avs, but I have no idea what they did.