A character throws their back out
Human beings are a fragile sort. Apparently. If an alien were to use American television to suss out the state of our back health, they would probably think we are a super weak species. Everybody is always throwing their back out on TV. Or maybe it’s not just the back, but it’s usually some sort of middle-body injury that completely debilitates them and they can ambulate.
I probably should jinx myself here, because as soon as I finish typing this, I’ll probably throw my own back out getting up from this chair. But this seems like a very easy shortcut to either have the audience laugh at (not with) a character or have one character take care of another. I get it. It’s easy block when they film it, and you don’t really have to be too specific about causes and treatments. People understand the vague concept of back pain. I get it.
But why does it always have to be the back? I get migraines on a far more frequent basis than a backache, and this could be a recurring device you can come back around to on a slow writing day. Perhaps the back gag, or really any joke that depends on an injury, is just based on our innate desire to laugh at folks who get hurt or embarrassed. If we didn’t love to see folks suffer, this wouldn’t even be a thing, much less an overused cliché that we’re tired of seeing. We’re monsters, if you didn’t know.
Examples: The Middle, Friends, Seinfeld, and Modern Family