Frankfurt's scoring woes continue
Frankfurt have not scored in their last five games since February 2 to move to 39 points in fifth place, behind Schalke, who won on Saturday.
Hannover had won their last five home matches but collected just one point in moving to 34.
Under steady snow throughout the game, the only chance of the entire first half went to Frankfurt in the 21st minute as Takashi Inui was fed a ball that he looped over Hannover goalkeeper Ron-Robert Zieler, but Christian Schulz was there to head clear of danger.
Hannover, who did not have a single shot on goal in the first half, nearly went ahead in the 46th minute but Frankfurt goalkeeper Kevin Trapp deflected Mame Biram Diouf's shot from the edge of the box over his crossbar.
The hosts were close again two minutes later as Pirmin Schwegler stopped Didier Ya Konan's shot from eight yards out at the line.
Frankfurt found the back of the net in the 49th minute but Alex Meier was ruled offside.
Meier had another chance 12 minutes later but his attempt went just over the crossbar from 17 yards out.
Hamburg ended a two-game winless streak to climb into sixth place as Rudnevs scored the only goal of the match in the 50th minute.