There are many phrases that can be used as synonyms for "twist the knife in the wound". One such phrase is "pour salt in the wound", which means to make a bad situation even worse by adding insult to injury. Another similar phrase is "rub salt in the wound", which also implies adding pain to an already painful situation. "Rip open old wounds" can be used to describe bringing up painful memories or experiences, similar to how twisting a knife in a wound would cause pain. "Kick someone when they're down" is a phrase used to describe adding insult to injury in a situation where someone is already vulnerable.