The spasms first surfaced Monday night late in the first half of the Knicks' loss to the Houston Rockets.
Anthony attended the game in street clothes.
The star forward said he has made progress in recent days, according to reports.
Anthony took part in some shooting drills for the first time since his injury prior to Friday's game.
"From not being able to straighten my back up to not even being able to get out of bed to walking and shooting a little bit, I've made huge strides in the past couple of days," Anthony said.
Anthony said the back spasms are related to a muscle issue and are not an indication that he has a disk problem, which would indicate a more serious condition.
Anthony added that he still has spasms but that "80 percent" of them have subsided. He said he was in severe pain Monday night when the spasms first set in.
"I couldn't talk,'' Anthony said. "Teammates were coming up to me and asking me if I was OK. I couldn't breathe, I couldn't talk, couldn't move. I couldn't scratch my forehead to see where I was at. I never experienced any type of pain like that."
Anthony's status for Sunday's game against the Miami Heat is uncertain. Anthony participated in shootaround Sunday morning and was listed as questionable for the game.
"I'm worried about how my back is going to react to what I just did right now, so I'll go in there and get some more treatment and see how it feels tonight and the morning," said Anthony, who attended Friday's game in street clothes.
This is the second injury for Anthony this season. He revealed last week he is playing with discomfort in his left knee, which he said first surfaced during the second game of the season. He said on Friday that the knee and back injuries are unrelated.
Anthony is leading the Knicks in scoring with 23.2 points per game. Their next-highest scorer entering Friday is Amar'e Stoudemire with 12.1 points per game.
New York has lost two straight without Anthony and 11 of 13 overall.