Sometimes the knife gets stuck in the left hand, and the right hand can hold anything. I've seen people hold the knife in the left hand and knife in the right hand. I've noticed this bug way back on PTS, still not fixed.
Yes I see knife strangely attached to weapons quite often but the picture I found was so good since it almost looks like it's held in a normal grip.
I had a little dancing phoenix missile in front of me yesterday while I was using the RL - it that a similar thing?