Gallinari will have surgery during the week to repair his injured knee, which sustained torn meniscus - according to reports.
The latest health problem comes after a torn ACL in Gallinari's left knee cost him all of the Nuggets' 2013-14 campaign - their first season without play-off action in 11 years.
Gallinari was still in the early stages of his return when he received the diagnosis, which is in connection with two ACL surgeries he underwent on his right knee.
The Italian averages 7.8 points and 3.0 rebounds this season, but posted his best game of the year in a 19-point outing against the Indiana Pacers on Saturday.
Gallinari missed games earlier in December due to bone bruises in his right knee.
Prior to the latest diagnosis, Gallinari said he had wanted to play through the discomfort given he had missed 19 months of basketball.
The blow comes in addition to injuries to JaVale McGee (leg) and Randy Foye (quad) ahead of their clash with the Charlotte Hornets on Monday.