71 Y.O. Betsey Johnson SORRY GOTTA SPLIT

9/12/2013 3:30 PM PDT BY TMZ STAFF
She's 71 years old ... but that didn't stop legendary designer Betsey Johnson from doing a FULL SPLIT on stage Wednesday at Fashion Week ... while wearing a hilarious pair of pink briefs.

Who knows, maybe she's got an extremely high threshold for pain ... she is holding what appears to be a prescription pill bottle after all.

Either way. Respect.