The 16-year-old was bouncing around in the backyard with her big sis, Khloe Kardashian, and somehow she managed to get hurt so bad that she had to go to the hospital.
It sounds like it wasn't anything too terrible, though, because she Instagrammed this picture from the hospital with the caption "in the hospital thanks to @khloekardashian. (Look at her page for the reason why 😂) my mom said 'never thought I would take u to the doctor for a trampoline accident at this age)' this means war Khloe. Ps. It was painful taking this photo."
Khloe posted a picture, along with her version of the story, joking back, "Kylie this is proof you did it to yourself! Sorry not sorry! Just kidding I am sorry my little bug a boo!! Let the war continue!!!!"
In the photo collage (below), Kylie seems to be having a great time and then boom, she goes down clutching her back.
Still, we're not sure Khloe was simply an innocent bystander in this scenario. In fact, she herself posted a pic of the two of them fighting on the springy surface with the caption "This started out calm and ended in a war! Sorry @kyliejenner."
It also looks like Kim Kardashian got in on the action (in a crop top and skirt, of course), but both of the older girls managed to avoid getting injured.
Get well soon, Kylie!