Luka Doncic's knee bleeding issues returned on Monday when the LA Lakers took on the Brooklyn Nets at Barclays Center. Doncic and his bleeding knees have always been a mystery to NBA fans. Whenever he's donned white compression leg sleeves, there's often blood stains on either of his knees, leaving fans confused about why this is a frequent case.Most Lakers fans learned of the issue after spotting it during Monday's game. It was Doncic's right knee this time that had a blood stain on it. However, unlike previous times, there was a possible reason behind the issue. Doncic hit his right knee on the hardwood during a first-half play, which caused the bleeding.One Lakers fan reacted after spotting the blood stain:"Why does this keep happening?"Another pointed out the reason, saying:"Hit his knee on the floor pretty hard when he turned his ankle. it didn’t just happen randomly"One said:"Nico cursed Luka health"One fan added:"We starting to see why Dallas traded him, 26 years old and bleeding, holding his back, etc…"Another wrote:"Really gives his blood sweat and tears for this"Banged-up Luka Doncic struggles in loss to BrooklynLuka Doncic had a subpar outing for the second straight game. The Lakers star, who has been dealing with a back issue, shot poorly against the Brooklyn Nets in Monday's contest, going 30.8% from the field. He had a triple-double with 22 points, 12 rebounds and 12 assists, but another underwhelming night with his execution contributed to LA losing 111-108.Doncic was caught up with the referees not offering him a fair whistle. He even said that it was "unfair" during his post-game press conference."It wasn’t fair. … but just gotta play the game," Doncic said.The Slovenian made four trips to the foul line. He didn't earn a single attempt in the first half despite playing downhill and through contact. As a team, the Lakers made just two free throw attempts, so it was a game-long trend.However, Luka Doncic and Austin Reaves, the lead offensive anchors in LeBron James' absence, shot a combined 11-of-40, which deserved more criticism than the refs for the loss.