Police are appealing for witnesses after the driver of an unknown vehicle failed to stop after a collision with a motorcycle which threw the rider off.
It happened in Long Street, Attleborough, at about 10.45pm on Wednesday.
A cyclist came to the aid of the rider, who suffered a leg injury and was taken to hospital.
Officers want to speak to anyone who witnessed the collision or may have seen the vehicle that did not stop before or afterwards.
Contact PC Wendy Frary at Wymondham Roads Policing Unit on 101.