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Running back Trent Richardson’s path to Canton via Baltimore seems headed for a detour through a hospital.

Richardson probably needs arthroscopic knee surgery, the Baltimore Sun reported Thursday, due to a pre-exisiting condition.

Richardson has transformed his body, dropping 20 pounds, and is attempting a comeback with the Ravens. He recently said he sees himself as still capable of making the Pro Football Hall of Fame.

If he can get back to full speed early enough in camp, the No. 3 pick in the 2012 draft figures to have a chance to make the roster with the Ravens, his fourth NFL team. Richardson previously missed some time in spring workouts with a hamstring issue.