Graphic video has emerged of a bull’s leg being broken during an Adelaide rodeo last night, drawing condemnation from the RSPCA.

The footage, taken by a spectator, shows the bull bucking as the rider tries to hang on during the Professional Bullriders Australia event at Adelaide Entertainment Centre.

The competitor is then thrown to the ground, but quickly recovers and rushes to the side of the enclosure.

Meanwhile, the bull continues to jump with a broken leg as organisers try to restrain it.

The bull's leg was broken during the rodeo.

Organisers were seen frantically trying to control the animal.

RSPCA South Australia is now investigating the treatment of the bull following its injury.

The RSPCA and animal rights protesters had campaigned to have the event cancelled.

"Well that was horrifying vision and you know, to think that the Adelaide Entertainment Centre would actually market this as family entertainment..." Dr Rebekah Eyers from the RSPCA SA told 9NEWS.