Washington Capital center Ryan Walter underwent surgery to remove torn cartilage in his left knee yesterday at Arlington Hospital, then promised, "I'll be back quick."

Despite his enthusiasm, the hockey team's No. 1 draft pick will be off the ice four to six weeks, according to Dr. P. M. Palumbo Jr., who performed the operation. It probably will be another two weeks beyond that before Walter came make his NHL debut.

"It's an inopportune time and it's frustrating," Walter said, "but it'll all right. I'm going to stick around here and work on it. It's a lot simpler than the operation on my other knee (in 1975). That time I hit the goal post and the goal post didn't move."

Walter injured the left knee while playing lacrosse with a younger brother at his New Westminster, british Columbia, home in August. It was decided to immobilize the knee in the hope that rest would heal the damage. It didn't.

"Ripped cartilage is something you can walk on and run on, but when you turn the wrong way it will lock," Walter said. "After two weeks' rest it felt okay, but when I skated Monday it locked."

So yesterday Palumbo made an arthroscopic examination, detected three tears in the cartilage and immediately operated to remove the cartilage.

"When he was here immediately after the injury, we took an orthogram - injecting fluid into the joint to show the outline of the cartilage," Palumbo said. "On the basis of what we saw, we thought with rest it might get well. That was worked with Guy Charron and other athletes I've treated. But the knee wouldn't withstand the skating. Today when we made the arthroscopic exam, we found the injury was worse than the orthogram had showed."