Twins catcher Joe Mauer, who had his knee scoped in December, on Tuesday had an injection in the same knee to lubricate the joint.Twins General Manager Bill Smith confirmed that the All-Star catcher had the injection on Tuesday in Fort Myers.``Joe Mauer received a shot of medication to lubricate the knee joint,'' Smith wrote in an e-mail. ``We will have him proceed slowly tomorrow, then work towards getting him back to full speed on Thursday.''Mauer has been unable to go full speed in camp as he tries to distance himself from his most recent surgery. He has not been allowed to catch pitchers in the bullpen, but has participated in other drills. It sounds bad, but many athletes have had injections in their knees. Nick Blackburn and Texas' Josh Hamilton, for example, have had injections of Synvisc in their knees to help provide some lubrication. In Blackburn's case, it allowed him to run again,lose weight, and reach the majors.Of course, neither Blackburn nor Hamilton have to squat behind a plate for nine innings.A cause for alarm? Not quite. But there should be some concern as Mauer tries to get behind the plate again. I was told by an expert that synthetic lubricants and solutions have been "very" effective over the years. Blackburn had 90 percent of his cartilage removed after the 2003 season and has had good results with Synvisc.