For more than a decade, Dan Hampton has been the heart of the Chicago Bears' defense. With Hampton in action, the Bears won their first four football games last year. When yet another knee injury knocked him out for the rest of the season, the Bears lost eight of the next 10 games.

Now Hampton is back for his 12th, and probably final, season. His knees are shot. He talks about them all the time: The pain. The surgeries. He has had 10 arthroscopic procedures in which surgeons removed bone chips and smoothed out damaged cartilage. Each knee has had five of these operations.

In interviews, Hampton says he wants to play because he loves the game and believes he can still contribute to the team. Just getting in the opening game against the Seattle Seahawks made him the second Chicago Bear in the club's history to play in three decades from 1979 to 1990.

But Bill Walsh, former coach of the San Francisco 49ers and now an NBC sports commentator, said Hampton should retire. "Ten knee operations!" Walsh exclaimed in a television broadcast. "He talks about his knees -- they're so stiff he can't walk." Hampton, who turns 33 tomorrow, could end up in a wheelchair if he doesn't quit, Walsh said.

For the Bears, Walsh's statements were a call to battle. "Everybody is entitled to their own opinion," shot back Bears coach Mike Ditka. "It is unfortunate that some people . . . sometimes don't think before they speak."

Hampton, who declined to be interviewed about his knees, released a blunt statement: "I don't have any doubts about what I can do this year."

Despite this show of confidence, Hampton's 6-foot-5-inch, 270-pound frame has taken a formidable beating over the years, including 15 broken bones, 300 stitches and so much damage to his eight fingers that he cannot open them fully. But it's his knees that cause him the most trouble. Degenerative arthritis and damage to his kneecaps make it so painful to bend the knee joints that he comes down stairs sideways.

This inevitably leads to the question on everyone's mind, from Walsh's to Bears president Michael McCaskey's: How long can, and should, Hampton play?

Although Ditka has said it is up to Hampton to decide when to quit, the coach already is "platooning" his defensive tackles, rotating Hampton, William "Refrigerator" Perry, who also suffered a knee injury, and Steve McMichael in an effort to lower the chances that any of them will be injured.

But should Hampton be in there at all?

"A lot of Dan's injuries have been to the undersurface of the knee cap rather than the weight-bearing surfaces," said Bear's team physician Clarence Fossier. But he said that Hampton has had cartilage removed from the knee and "it is not a normal joint surface."

Last year in October, Hampton had arthroscopic surgery on his left knee, its fifth such operation, then had the right one done -- also its fifth -- in November. No one expected him to return to pro football, though the orthopedic surgeon who did the operation gave him permission to play.

"Ten surgeries sounds terrible, but it isn't that bad," Fossier said. "Sure, he does not have the normal knees of a 33-year-old. But is he condemmed to a knee replacement at age 50? I don't think so."

Will he make it to the end of the season? Even Fossier is doubtful. He said Hampton's knees have been swelling up again, both from the practice and preseason games, and have already had to be drained once.

"He played this week {against Seattle} and felt pretty good at the end of the game," the doctor said. But "it would be miraculous for him to play the whole 16-game season."