I'm at the age where my back goes out more than I do.

This joke hinges on a clever bit of wordplay, taking a common idiom and twisting it for comedic effect. The phrase "my back goes out" typically refers to a sudden spasm or injury, a lamentably frequent occurrence for many as they get older. However, "goes out" also means to leave the house for social activities or entertainment. The initial setup cleverly plays on this double meaning, immediately setting up the relatable struggle of aging and its physical challenges.

The humor is further amplified by the relatable context of getting older. As people age, they often experience more aches and pains, particularly back issues, and their social lives might naturally slow down compared to their younger days. The punchline, "Last Saturday it went out to dinner without me," takes this personification to an absurd and hilarious extreme. It vividly paints a picture of the back as an independent entity, enjoying a night out while its owner is left behind, emphasizing the frustrating reality of an uncooperative body. It's a humorous nod to the indignities of getting older, where sometimes it feels like your own body has a mind, and a social calendar, of its own.