Robert Griffin III after suffering his injury

The NFL Players Association is expected to decide soon, perhaps Friday, whether to demand a formal investigation of the Washington Redskins’ handling of the knee injury suffered by quarterback Robert Griffin III under the sport’s collective bargaining agreement, a person familiar with the situation said Thursday.

The union also issued a public plea Thursday for the Redskins to improve the quality of the playing surface at FedEx Field.

Griffin is recovering in Florida after undergoing surgery there Wednesday on two torn ligaments in his right knee. Griffin’s brilliant rookie season ended when he left Sunday’s playoff loss to the Seattle Seahawks after re-injuring his knee. He was playing in his third game since he suffered a mild sprain of the lateral collateral ligament in that knee.

“Our medical director, Dr. Thom Mayer, has been in contact with the Redskins and has asked for a report on Robert Griffin III’s medical diagnosis and treatment,” George Atallah, the union’s assistant executive director of external affairs, said by telephone Thursday.

Under the CBA, the league and union have a joint committee on player safety and welfare. The CBA gives the union the right “to commence an investigation before the Joint Committee if the NFLPA believes that the medical care of a team is not adequately taking care of player safety.”

If the union initiates a formal inquiry under that provision, two or more independent physicians would be chosen to conduct an investigation and issue a report. The CBA says that “their recommendations as to what steps shall be taken to address and correct any issues shall be acted upon by the Joint Committee.”

According to a person with knowledge of the situation, the union’s focus is whether the Redskins followed the recommendations of their medical staff about when to play Griffin. The union’s probe does not focus on coaching decisions made by Mike Shanahan, other than the issue of whether he followed the recommendations of doctors, the person said.

According to that person, the union has sought information going back to the Dec. 9 game against the Baltimore Ravens, when Griffin originally suffered his LCL sprain on a hit by Haloti Ngata.

Shanahan has said he followed the recommendations of doctors.

James Andrews, the orthopedic surgeon who operated on Griffin and is on the sideline for Redskins’ games,  told USA Today last weekend that he did not clear Griffin to return temporarily to the Ravens game, in contrast to Shanahan’s version of events. But Andrews later told The Washington Post that there was “a communication problem” between him and Shanahan.

Andrews said he didn’t get a chance to examine Griffin but gave Shanahan a hand signal to indicate that “I guess he’s okay” to play. Griffin, after missing one play, returned to that game for four plays before leaving for good.

Griffin remained in Sunday’s playoff loss to the Seattle Seahawks after appearing to re-injure his knee on a first quarter play. Griffin and Shanahan said later that the quarterback urged Shanahan to leave him in the game, and Shanahan agreed.

DeMaurice Smith, the union’s executive director, told ESPN earlier this week that the union had initiated formal investigations of teams’ handling of injuries on “at least three occasions” under the CBA, which was completed in 2011. Smith said in that televised interview that the union was looking into Griffin’s injury because “there was enough of an inconsistency or a question about whether the process of evaluating the player occurred, whether he was cleared to play, not cleared to play.”

Of the condition of the field, Atallah said Thursday: “The coaching staff and players for both teams have spoken out against the quality of the field during Sunday’s game. We would hope that significant improvements would be made.”

Seahawks Coach Pete Carroll was highly critical Monday of the condition of the field during Sunday’s game. It is unclear if the condition of the field contributed to Griffin’s injury. Shanahan said Monday he might be receptive to the possibility of a future switch to an artificial playing surface at FedEx Field.