Carolina Panthers defensive end Charles Johnson underwent arthroscopic surgery on his right knee on Friday, Joseph Person of the Charlotte Observer reports. According to Person, Panthers general manager Marty Hurney described the procedure as a "minor clean-out" and Johnson tweeted that his surgery was a success. Johnson's availability for the team's OTAs and mini-camp is unknown at this time. Signed to a six-year, $76 million contract that included $36 million in guaranteed money last July, Johnson had 40 tackles and a team-high nine sacks in 15 games last season. Johnson missed the final week of the regular season with a back injury. Source: Mac's Football Blog
