Greater Manchester police (GMP) say the man, who is thought to be in his mid-20s, ran across the southbound carriageway after initially being on the hard shoulder.
The lorry driver attempted to avoid the man by moving into the second lane but the man ran into the vehicle's path.
Police say the driver is deeply shaken after the incident and have called for witnesses to come forward.
"The injured man is described as in his mid-20s and of mixed race, wearing a long-sleeved white shirt with pink and blue vertical stripes," a GMP spokesperson said.
"Anyone who witnessed the incident, or saw the man on the hard shoulder prior to the collision, is asked to call motorway police."
The southbound carriageway was closed for about two and a half hours following the incident and was only re-opened at 22:45 BST last night.
Click here to run an energy price comparison, and see if you could be paying less for your gas and electricity.