An old mod idea I had a year ago before I realized I don't have the correct knowledge nor PC to make a fully functional Sims 4 mod, but I think this concept could be pretty interesting! I'm just going to write down the entire original idea I had
Simple version: There's a chance your sim will break a bone randomly, especially when doing certain interactions such as ice skating, playing with toddlers etc. When the sim breaks a bone a cast will magically appear on one of their limbs. Children and elders would have a slightly bigger chance of breaking a bone. Sims won't really notice, they'll just be slightly uncomfortable.
Not so simple version: It starts off with a +5 sad moodlet telling you about how their body really hurts and that they should go to a doctor, you will then have to send them to a rabbithole to a hospital, and they'll return about 1hr later with a cast on a random limb, as well as 3 negative moodlets (and one positive, but only for kids and teens)
Amongst these there would probably be an uncomfortable 7, letting you know they've broken something, a sad +4 moodlet,, and a dazed +2 moodlet from the medication.
the entire thing lasts for 4 days, but the moodlets lessen gradually day after day, the dazed one disappearing already after 12 hours.