The injury came to light when Gibbons was asked about Johnson's struggles this season, but it doesn't appear to be a major cause of concern for the organization.
"He's not tipping pitches at least that you can see," Gibbons said. "He's had some knee issues, his landing leg.
"He gets a little tendinitis, nothing major that you can't perform, but when you land on it if you get that little stinger. We're trying to figure [out why he's struggling] too."
The vast majority of Johnson's problems this season have come when he is pitching out of the stretch. He has allowed the opposition to hit .380 with a .441 on-base percentage with runners on compared to a .225 average and .281 OBP with the bases empty.
A lot of the issues have been related to poor command. Johnson either has a tendency to nibble around the zone and miss the plate while also throwing a high number of pitches or get way too much of the strike zone while leaving the ball up in the zone.
The club has attempted to experiment with a number of different techniques to solve the problems, but so far nothing has really worked on a consistent basis and it has resulted in Johnson having a 6.08 ERA in 14 starts this season.
"They've tinkered with trying to move him to the first-base side of the rubber to make it a little bit easier to get to that part of the plate consistently," Gibbons said. "We need him to start winning some games."
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.