Guy Charron, the Washington capital's captain and most popular player, underwent surgery yesterday to repair torn cartilage in his left knee.

The operation was performed at Arlington Hospital by Dr. Pat Palumbo, who said Charron had suffered "a massive tear of the medial meniscus. It was inside the joint and locked the knee."

Charron was injured during the World Championships in Moscow, where he represented Canada for the third straight year.

"I was going for the puck and I was falling to the ice," Charron said "Greg Smith was behind me and he couldn't stop and landed on my leg."

Charron suffered stretched ligaments in the same knee at the 1977 World Championships in Vienna and the knee was placed in a cast. Just before the 1977-78 season began, he suffered a slight tear in the cartilage while playing tennis. There was fear he would need an operation then, but he responded to treatment and was able to start the season.

Charron has not missed a game with the Capitals in three seasons since being acquired from Colorado in August, 1976. However, he was troubled by the knee at intervals this season.

Charron collected 36 goals his first season in Washington and 38 the second. This year the knee trouble, reduced ice time and the pressure of the captain's role combined to reduce his production to 28.

At season's end, Charron was chosen the team's most popular player by the Washington Capitals Fan Club.

Charron is expected to be ready for the start of training camp on Sept. 15. Following a lengthy recuperative period, he will begin an exercise program and a buildup with weights.