Keyframe not animating bone from initial position? I'm new to blender and even newer to animation.

I was working on animating my enemy model for the game I'm developing and everything went fine with the right leg.

However, when I went to edit the left leg, I discovered that it wasn't being saved in the keyframe for some reason and instead was edited so every frame has the left leg in the air. 

The record button is on but nothing seems to be making it move into the air. The right leg edits without a hitch.

Frame 20:



Frame 40:



Any idea why this could be happening?
You need to set an initial keyframe for any animated data, including armature bones, in the first frame. The pelvis left bone is set to that position at frame 40, but because there's no keyframe before it, its position is interpolated all the way to the starting frame.