Johnson sat out an April minicamp for the team to continue his recovery from the problems, but has now been declared fit having had surgery to fix them.
The knee injury hampered Johnson's 2013 campaign, with fluid having to be drained from it on a regular basis.
He told Fox Sports: "I feel pretty good right now. I'm out here working, taking all my reps for the most part. Knee's feeling good, hand's feeling good. I can't complain."
Johnson has caught for over 1,000 receiving yards in five of his seven NFL seasons.