The Washington Redskins, concerned about the health and age of running backs John Riggins and Joe Washington, are actively seeking to trade for an established, younger running back.

General Manager Bobby Beathard, here this week for the National Football League's annual winter meetings, told The Washington Post he feels the Redskins have a "problem" at running back and said he had talked with representatives of every NFL team since the Super Bowl, inquiring about the availability of what he said would be a "backup" running back at this point.

But that situation could change if Riggins, who recently met with Coach Joe Gibbs to discuss his future, tells the Redskins he will retire.

Riggins, who is a free agent, left last week for a three-week vacation in Africa and refused to comment on his future before his trip. The Redskins expect Riggins to tell them of his plans before the April 30 draft.

In an unrelated matter, Redskins owner Jack Kent Cooke, who is not attending the meetings here, said by telephone today from his Virginia office that quarterback Joe Theismann "will be signing a contract soon."

Theismann agreed to a two-year extension of his current contract last July, but has not yet signed it. The contract extension, when and if signed, is to run through 1987.

"There is no problem," Cooke said of the situation that was to have been resolved last July.

Theismann could not be reached for comment.

Beathard, meanwhile, acknowledged what many around the league have been saying -- that the Redskins want and need a running back.

"I think we'd be kidding ourselves if we weren't looking," Beathard said. "Assuming John Riggins is 100 percent healthy and Joe Washington's knees are fine, we'd still have to look for a good running back.

"It's our most important position right now."

Riggins, 35, was bothered by a back injury most of last season, during which he gained 1,239 yards. Washington, 31, missed nine games with a knee injury. Washington gained 192 yards on 56 carries last year, but indicated after the season he would like to play in 1985.

Beathard said the Redskins' search for another running back has "nothing to do with" the highly publicized incident involving Riggins at the Washington Press Club Salute to Congress dinner in January.

Riggins told Supreme Court Justice Sandra Day O'Connor, "Loosen up, Sandy baby," and later fell asleep on the floor during a speech by Vice President George Bush.

However, sources say the Redskins are upset about Riggins' behavior off the field (witnesses at the Jan. 30 dinner said Riggins was drinking wine before his 45-minute snooze) and are concerned about his health and image.

Riggins has refused to comment on the incident, as have Cooke and Gibbs.

"We had a long talk a week and a half ago," Gibbs said today. "I wanted to find out how he was feeling. It was a good talk, a long discussion. He is starting to feel better, but he wants to wait and see how he feels before he makes a decision on his future."

Gibbs said he didn't know what that decision would be.

"I'm very interested in it," Gibbs said. "I'm not sure if he knows yet. He is still resting up and evaluating his situation."

Beathard added: "We're certain John will make his decision before the draft. But we're not going to force him to talk to us."

Still, Beathard said, the Redskins plan to go into the draft "prepared as if we have a problem (at running back)."

Beathard said he has spoken with every team in the league about trades, as he does every year at this time. So far, none is interested in trading a running back. He said he could not mention specific running backs who interest the Redskins. "That would be tampering," he said.

He did say that wide receiver Charlie Brown, who missed seven games with a stress fracture of his fibula and a knee injury during the 1984 season, is not being offered as part of a trade. Brown, during a recent trip to Texas, indicated that he thought the Redskins wanted to trade him.

"Charlie is over his rehabilitation and working out and we want to have him with us," Beathard said.

"As we get closer to the draft, things should begin to happen. It's a bit premature to hear now," Beathard said.

If the Redskins are unable to make a trade for a running back, they are considering the possibility of making a trade to improve their position in the draft, so as to obtain a running back in the first round. The Redskins currently have the 23rd pick in the first round.

North Carolina's Ethan Horton and Kentucky's George Adams, perhaps the two most coveted running backs in the draft, almost certainly will be gone by the time the Redskins make their first selection.

"I've talked to teams about trading up, but there has been nothing encouraging," Beathard said. "At the same time, I don't know if we would trade up because we'd have to pay a price for it, and I don't know if we're willing to do that."