As our esteemed colleagues over at Antiquiet pointed out, Cheng can apparently lift his leg on command and express himself vocally.
In the wake of his accident, his insurance company cut off coverage, leaving Cheng's family in a tough situation, having to pay for an extensvie and expensive surgery that they couldn't afford - prompting the Deftones to team up with an organization, One Love for Chi, to raise funds to help pay the medical costs. That organization's site is currently down, probably swamped with traffic, but you can visit it here and donate/read more about his situation.
Below, watch Cheng lift his leg on command.
Good luck Chi, and hope your successful recovery continues!