Ushijima has a really huge crush on Oikawa, that's why he always says to him that he should've come to Shiratorizawa.
But since Oikawa is Iwa-chans boyfriend, Ushijima once got really mad at Shittykawa so in one match he spiked the ball with his abnormal power against his bad knee and the dorky Setter ended being hospitalized.Since this day his knee got worse and he is medically not allowed to play volleyball that much anymore. Trashykawa often limps and he'll have serious problems when he gets older because the doctors never properly look at it. He may will end with a perpetual limp soon enough, maybe in his early 20s.
I'm really sorry for being sadistic, but I like suffering. •᎑•