Johnson, 25, missed seven weeks last season after suffering a sprained left knee in Week 2 against the Carolina Panthers. He returned in Week 11 and averaged 84.1 yards in his final seven contests, finishing with 60 receptions for a team-high 851 yards and eight touchdowns.

Johnson aggravated the injury two weeks ago during off-season mini-camp.

"He wasn't really comfortable coming out of (mini-)camp, so we said, 'Hey, let's go scope it and see if there are any issues,'" Texans Coach Gary Kubiak told the team's Web site.

Johnson should be ready for training camp at the end of July.

"I feel good right now," said the two-time Pro Bowler. "The knee didn't swell up or anything. It has a little bit of swelling, but nothing major."