Pittsburgh quarterback Terry Hanratty threw for two touchdowns before reinjuring his rib as the Steelers held on to edge the Washington Redskins 21-16 last night.

A late Redskin comeback attempt featured a final period touchdown, but the rally was stopped by a key goal-line in terception by Glen Edwards of the Steelers.

Hanratty fired his pair of touchdowns in the first period as Pittsburgh built a 14-6 halftime lead. Curt Knight kicked two field goals in the first half and added another in the third period.

Joe Gilliam, back-up quarterback for the Steelers, replaced Hanratty, who suffered a rib injury, and passed 46 yards to Barry Pearson for a score in the final quarter. Billy Kilmer of the Redskins ignited a comeback with a touchdown pass to Larry Brown to bring the score to 21-16 but Edward's interception ended the threat.

Pittsburgh boosted its record to 7-1 and widened its lead to 2 1/2 games in the AFL Central Division.