“Boobs or Knees?” – Jane Pain is stirring the latest online optical illusion

Optical illusions are frequently ‘winning the internet’ and here’s yet another fad that’s sure to cause a stir.
Argentinian lingerie brand, Jane Pain have created the illusion by placing underwear over the bend of a knee/armpit/elbow for their cheeky new lingerie campaign. It’s all backed by the supporting claim “If it can make your knee look sexy, imagine what it can do in the right place.”
Cue “hotdogs or legs” version 2…. See below.
This pic belongs to a good lookin’ arm pit:

This cheeky snap belongs to someones knees:

Nice elbows!

We’re still stumped on this one: