The guard was injured after landing awkwardly with 7:17 remaining in the third quarter, headed to the bench and did not return, but a report says he avoided a serious injury and will have another exam in a week.
X-rays on the knee came back negative, but an MRI showed the strain in his left knee.
When he left the game, MCCollum had scored 10 points in 22 minutes.
"I went up for a layup, a left-hand layup, and big fella [former Blazer Jakob Poeltl] blocked it," McCollum said after the game.
"I landed on my foot, kind of trapped my foot on the ground, felt my knee kind of twist. I was in pain. It hurts. You never want to get hurt, man. Not ever, especially at this point in the season.
"There's nothing I can do about it but rehab and see what they say. I can walk, but I'm not sure what the extent of it is. Obviously, on the replay it's hard to kind of see it because my foot is trapped and his body is there. But there's some discomfort, some pain in certain areas. So we'll see what happens."
McCollum is second on the Trail Blazers in scoring this season, averaging 21.3 points per game in 68 games.
He also has been one of the most reliable players in the league over the last few seasons, as he had missed only one game this year, which resulted in a 22-point victory over the Phoenix Suns on Dec. 6.