Indeed good luck with translating that, I think I do get its meaning though.
One way would be to describe the meaning of those words.
I will take a shot at this one; I can't take any liability to the accuracy of this.
"arm" meaning both arm as well as poor(ly), and "bein" means leg
And "besser dran" meaning better off, but also means something like better attached.
"dran" also means something like ~at it~ as in "du bist dran" its your turn.
"bein ab" means something like, leg detached (apart).
So there actually are several translations possible, that's also the irony in it.
Phew,
I hope that helps.