It's a subject that has been whispered about in hockey circles for some time.
It has been the cause of some major battles between the National Hockey League and the NHL Players' Association.
It often has created conflict between team management and players.
It's the concept of having injured players examined and diagnosed by team doctors.
It's a very touchy subject, partly because of the legalities involved. So let's start by saying that the illustrations that follow are in no way meant to suggest that any team doctor is incompetent or lacking integrity.
Teams have to have their own medical staffs. Hockey is a violent game, and injuries of varying severity are common. Sometimes, as in the case of the cut throat suffered by Buffalo Sabres goaltender Clint Malarchuk, a player could die if immediate help were not available.
Doctors usually enjoy working for hockey teams. A common practice is for a team to have three doctors on staff. Barring any serious injuries, each is on call for one period, but gets to watch the game for the other two.
The pay is good and the patients are usually easy to handle. Because the teams are willing to make extra payments, the doctors have access to top-quality equipment. And the chance to associate with star athletes is a highly regarded perquisite.
But at the same time, player salaries are the highest single cost a team must absorb and as a result, there have been allegations that team doctors sometimes tend to lean towards the desires of their employers when it comes to making a determination about a patient's readiness to return to the ice.
The vast majority of hockey injuries are treated without incident. Often, even if there is a dispute, it never reaches the public domain.
In one such case, a player on an American team was threatened with suspension by his general manager if he did not return to the lineup. After a knee injury, he had been cleared to play by the team's doctors.
When the player refused, he was traded to another team where team doctors immediately ordered an operation and said that had the player tried to play, the subsequent damage would probably have ended his career.
Even though medical disputes rarely come into the open, one that did involved the many allegations that were made when Eric Lindros played for the Philadelphia Flyers. Eric's father Carl was openly critical of the team's medical staff.
Now, in Toronto, there is the Owen Nolan case. The Maple Leafs' staff of doctors, two of whom have since been relieved of their duties with the team, declared Nolan fit to play.
Nolan and his agent have disputed that assessment.
To the layman, there is no way to know who is right and who is wrong. Perhaps the doctors were right at the time of their decision and the situation changed.
Perhaps the doctors missed something. It happens. That's why second opinions are encouraged in medical matters.
But there is no doubt that in many cases, players don't trust team doctors. Those players feel -- probably without a great deal of justification -- that the doctors are pawns of the team.
For that reason, the NHLPA has a working arrangement with some specialists who are not employed by any team.
If a player wants to get a view other than the one offered by the team, he can do so. But sometimes, that action creates resentment in the team's front office.
There is no easy answer to the dispute. In fact, so far, no one seems to have offered for debate any workable solution.
It's just one more example of the continuing mistrust that exists between the two solitudes in the NHL.