Sugar Ray Leonard, the retired world welterweight boxing champion, underwent an emergency hernia operation Thursday at Holy Cross Hospital in Silver Spring and was reported in good condition, recovering without incident, the hospital announced yesterday.

According to a statement released by the hospital and Leonard's attorney, Mike Trainer, Leonard, 27, began to suffer pains in the groin area early Thursday and went to Holy Cross' emergency room for an examination.

"The diagnosis indicated the need for surgery, which was performed at 4:45 p.m. Mr. Leonard recovered without incident from the short period of surgery . . . It is expected that he will be released from the hospital within three or four days."

Trainer said there were no indications that Leonard's hernia was related to a boxing injury, nor was there any recent physical activity to which it could be traced. He said there were no signs that anything was amiss until Leonard felt the pains.

"At first, we thought it was appendicitis. He's a normal human being, subject to the same aches and pains as you and I," Trainer said.

He also said Leonard plans to resume his normal work schedule once he leaves the hospital, and will do commentary for Home Box Office during next week's middleweight title fight between Marvin Hagler and Wilford Scypion in Providence.

Leonard's boxing career ended a year ago when he underwent surgery for repair of a partially detached retina in his left eye at Johns Hopkins University Hospital in Baltimore. Although doctors pronounced him recovered and medically fit to resume boxing, Leonard announced his permanent retirement from the ring Nov. 9, six months to the day after the operation.