Board Thread:Questions and Answers/@comment-199.255.1.20-20130222140355/@comment-1672596-20130222141046

He's referring to the events of Twin Suns from Metal Gear Solid 4, where he had to lose his arms to save Solid Snake (specifically, he willingly cut off his right arm to save Snake from Outer Haven due to being otherwise unable to move in to aid Snake, and he lost the remaining arm when he was crushed by Outer Haven).