The Portuguese international, who had a frustrating afternoon is the subject of police questioning after an Evertonian suffered a suspected broken arm trying to retrieve the ball.
The fan was injured while reaching for the ball in order to pass it to Ronaldo who had won a throw in down the left hand side in the second half.
Everton and Manchester United officials have remained silent over the incident, which was not shown by TV cameras.
The injured fan confirmed to a Sunday newspaper that a complaint had been made to a local Merseyside constabulary after he had received treatment on his stud-marked arm.