Officers have released CCTV stills of a man they believe may be able to help with their enquiries into the collision, which occurred on Station Parade at the Junction with Robert Street just before 4.30pm on Friday 30 September 2011.
The grey-haired man who was wearing a green t-shirt and earphones is believed to have crossed Station Parade and headed towards York Place at around the same time the 89-year-old pedestrian suffered serious leg injuries when he was hit by an Asda articulated lorry.
The injured man is currently in Harrogate District Hospital in a stable condition.
Officers are appealing for the man in the green t-shirt and anyone who witnessed the collision to come forward with information.
Traffic Constable Tracy Smales, of Harrogate Roads Policing Group, said:
Unfortunately, the victim suffered very serious injuries to his legs in the collision and we are currently investigating the circumstances.
Considering the time of day the incident occurred it is likely that there were a number of people around who can help us with our enquiries.
The man pictured in the CCTV footage may well have information that could help the investigation and I urge him to come forward.