Hi, guys. I'm having trouble with skinning the biped to my model. I can't seem to understand why this is happening. When I make the verts on the sphere rigid to the leg bone, it deforms that part of the mesh. Any help would be greatly appreciated, thanks.

Before:
https://snag.gy/Qk12Bh.jpg

After:
https://snag.gy/SdD0e5.jpg