The victim was was found the Ardilea Park area of Downpatrick sometime between 3.30 am and 4 am on Sunday, 10 December.
One man has been arrested on suspicion of attempted murder.
Detective Sergeant Peter Stewart said: “Just after 4am police were called to a property in the Killough Road area of the town where they found a 22 year old man with serious stab wounds to his side and back.
He was taken to hospital by the NIAS for treatment to injuries which are not believed to be life threatening at this time.
“A 21 year old man has been arrested on suspicion of attempted murder and is currently in custody, helping police with our enquiries.
“We believe a knife may have been discarded after the assault and would ask the public in the Killough Road area to be vigilant and report any suspicious items they see to police immediately.
“We are also appealing to anyone who was in area between 3.30am and 4am and witnessed the incident, or who may have information that could help our investigation, to contact detectives at Downpatrick on the non-emergency number 101, quoting reference 401 of 10/12/17.
“Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime.”