Fernando Alonso passed a final medical test at Austin on Thursday and was declared fit to race for Ferrari in this weekend s United States Grand Prix.

The two-time world champion had been in back pain since bouncing on the Yas Marina kerbs two weeks ago during a battle for places at the Abu Dhabi Grand Prix.

The impact -- which was measured at a staggering 25G -- required precautionary hospital checks on the evening of the race.

He had further examinations afterwards before flying to the United States where the organisers  rules required him to have a further check-up.

Following a series of tests, Alonso was given the all clear to race.

After the examination he left the track to return to his hotel, skipping all media commitments.