If I remember correctly, tj was the one that asked for Ian’s leg to be injured when he found out Ian may be going to California to pursue his dirt biking career. I think Ian knew this whole time that it was Tjs fault but TJ didn’t know that Ian knew, that’s why he was shocked.
It was indeed tj fault, but one correction, he didn't ask for Ian be injured he ask them to restrain Ian which led to Ian incident. But this never would happen if tj wasn't selfish in keeping and controlling Ian. Also Ian knew since the incident, if you go back to him in the hospital he implies if tj said anything their relationship would be over in as instant. He knew from the very start.
Why did he say .
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.do you wanna break my other leg too?