10 Subtle Details That Make Joaquin Phoenix's Joker Incredible

3. His Straitjacket Stance

For almost the entire film, Arthur is a sinewy, twisted knot of a man, painfully thin to the extent that you worry that Joaquin Phoenix would have lasting damage done (and he did say it destabilised his mental condition to get to that point). He's also hunched, with his shoulders curled inwards and his spine curved. It's a posture clearly designed for visceral reactions, but it isn't without context too.

At one point, Arthur write a joke about a straitjacket that is too tight in his joke diary, he also seeks comfort at another point by emptying his fridge and climbing into it (at which point we find out the door looks the same as his former Arkham cell door did) and expresses his happiness at Arkham. He even tells the admin clerk about his crimes as a means to get locked up. It doesn't work but he tries because he wants to be there.

The reason for his posture is linked to the same thing: Arthur feels comforted by constricting his body as if he's wearing a straitjacket, pulling his shoulders across him and bending his back as if too tight. Even when he's not in Arkham, he's still wearing that jacket.