OK. Here’s what I did to make the rig behave well on the left leg (see picture).
[EDIT]Picture with bone names[/EDIT]
- In Edit Mode, select all bones and hit CTRL+N to align bone rotations.
- In Pose Mode remove IK solver and limits on following bones: UpperLegB.F.L, LowerLegB.F.L.
- Clear parent relationship for following bones: IK_lowerleg.F.L, IK_upperleg.F.L.
- Select Paw.F.L. Add an IK Solver contraint with following settings:
- Select LowerLegA.F.L. Add an IK Solver contraint with following settings:
Now you can move the IK_lowerleg.F.L and IK_upperleg.F.L bones around and you should not have the weird glitchy behaviour. When you have this behaviour, the IK chains aren’t setup properly and you will notice that when you TAB in and out of Pose Mode, the pose will be reset. Once it is fixed, your pose won’t reset when you TAB in and out of Pose Mode (you have to clear the rotation, location and scaling (ALT+R, ALT+G, ALT+S) to do so.
Also, now you can limit the rotation of the necessary bones so the armature doesn’t get into weird contortionist poses :).
This fixes your problem of weird behaviour but the rig for the legs isn’t the greatest for animation; its good for posing. I noticed you have not used null bones at all and that your entire leg is a chain; usually the upper and lower leg will form one connected chain while the foot bones will form a separate connected chain.
Look up some foot rigs like Mancandy, Ludwig and the one in the Blender book. These have been very useful to me.
Hope this helps.