The victim was walking along a footpath in Broxtowe Country Park when two bikes came hurtling up behind him.
One of the bikes hit him and the impact caused him to fall back into a ditch where he briefly lost consciousness.
The riders did not stop and it was left to a passer-by to call an ambulance.
X-rays revealed the man suffered a broken hand that required a three-hour operation. He also suffered deep gashes and bruising to his legs.
Officers have released a CCTV image of a motorcyclist they are looking to trace in connection with the incident, which happened at around 3.30pm on 5 July.
PC Charlie Flatters, of Nottinghamshire Police, said: “Off road motorbikes driven in public places is a growing issue for residents in the Broxtowe area. On this occasion a pedestrian has been left with injuries following a hit and run, which is totally unacceptable.
“The incident took place during the afternoon and there will have been a number of members of public present in the country park. I am appealing for any witnesses to come forward with any information they may have.”
Anyone with information is asked to call police on 101 quoting incident number 556 of 5th July 2021.