Byrne, who will be battling with Leinster's Rob Kearney for the Lions No 15 jersey in South Africa at the end of May, was caught in mid air by Dragons flanker Jamie Ringer as he attempted to catch a high ball.
But an Ospreys spokesperson played down the incident and said: "Lee's taken a knock to his knee. It's sore at the moment but we hope it's nothing too serious."
The 28-year-old was one of six Lions on show for the Ospreys alongside IRB World Player of the Year Shane Williams, Tommy Bowe, Mike Phillips, Alun Wyn Jones and Adam Jones.
But Byrne, who only returned to action two weeks ago after picking up a foot injury in Wales' Six Nations defeat to Ireland in March, failed to re-appear for the second half at the Liberty Stadium. Lions wing wizard Williams and James Hook crossed for the Ospreys but failed to grab the bonus-point to allow Munster to clinch the Magners League title without having to play another game.