Orr signed with Chicago, but his injuries limited him to only 26 games over the next three seasons. He sat out the entire 1977-78 season. By 1978, Orr had undergone over a dozen knee surgeries, was having trouble walking and barely skated anymore. However, in the summer of 1978, he decided to make a comeback. He played six games of the 1978-79 season and came to the conclusion that he could no longer play and informed the Black Hawks that he was retiring. He started a new role as an assistant to Chicago general manager Bob Pulford. He scored his last NHL goal and point against Detroit on October 28, 1978, at Detroit's Olympia Stadium.  Orr retired having scored 270 goals and 645 assists for 915 points in 657 games, adding 953 penalty minutes. At the time of his retirement, he was the leading defenceman in league history in goals, assists and points, tenth overall in assists and 19th in points. As of 2013, the only retired players in league history to have averaged more points per game than Orr are Wayne Gretzky, Mario Lemieux and Mike Bossy, all of them forwards. "Losing Bobby", said Gordie Howe, "was the greatest blow the National Hockey League has ever suffered".  The Hockey Hall of Fame waived the normal three-year waiting period for induction into the Hall and he was enshrined at age 31 - the youngest player living at the time of his induction in history. Orr was the eighth player to have the three-year period waived, the next two being Mario Lemieux (1997) and Wayne Gretzky (1999), after which the Hall decided that the waiting period would no longer be waived for any player except under "certain humanitarian circumstances".  His number 4 jersey was retired by the Bruins on January 9, 1979. At the ceremony, the crowd at Boston Garden would not stop applauding and as a result, most of the evening's program had to be scrapped at the last second due to the constant cheering. The crowd did not allow Orr to say his thank you speech until he put on a Bruins jersey. The day was proclaimed "Bobby Orr Day" in Boston and the event raised thousands of dollars for charity. He attended the Massachusetts Senate and House of Representatives and was given a five-minute standing ovation. Boston Celtics basketball superstar Larry Bird said in his pre-game inspiration that he always looked up at the rafters of the Garden at Orr's retired No. 4, instead of the retired numbers of Celtics stars such as Bill Russell, Bob Cousy, or John Havlicek.

Answer this question "What year did he retire?" by extracting the answer from the text above.
1978,