As the NFL and players union continues their probe of the Carolina Panthers’ handling of Cam Newton last weekend, they have another factor to consider – a knee injury to the Panthers’ quarterback.

League and union officials began speaking to Panthers’ medical personnel this week about the situation involving Newton, who stumbled near the sideline after taking a hit to the head in the fourth quarter of the Saints’ 31-26 wild card victory.

Newton was checked for a concussion in the medical tent behind the Panthers’ bench, but was cleared to return. The NFL’s enhanced concussion protocol requires players demonstrating vertical instability after a hit to the head to be taken to the locker room to be evaluated.

Newton said after the game his head was fine, but he was having problems with his eye after his helmet slid down following the hit by Saints defensive tackle David Onyemata. Newton did not mention anything about his knee during his postgame press conference.

Carolina interim general manager Marty Hurney said this week Newton was told to take a knee before reaching the sideline so backup quarterback Derek Anderson could get warmed up without the Panthers using a timeout.

But a team source said Saturday that Newton had been dealing with a knee issue that could have contributed to him stumbling to the turf.

Trainers checked out Newton’s knee a couple times during the game, although the injury will not require surgery, the source said.

This is the second time the Panthers have drawn scrutiny for their handling of Newton after a big hit to the head. They were cleared last season after the NFL and NFLPA found the Panthers followed protocol after Newton was drilled by a Denver defensive back late in a Week 1 rematch of Super Bowl 50.