 SPOILERS: Riggs intentionally dislocates his shoulder in this film  in order to get out of a straitjacket, then has to slam his shoulder  back into place. This becomes a running gag throughout the series,  where he slams his shoulder back into place after riding a  motorcycle off a bridge in _Lethal Weapon 3 (1992)_ (qv) and Ku  (Jet Li (qv)s character) dislocates both of Riggs shoulders in a  fight scene in _Lethal Weapon 4 (1998)_ (qv).