Cristiano Ronaldo could miss Man Utd vs Crystal Palace after he injured himself during his "SIU" goal celebration

Manchester United are currently sweating on the fitness of Cristiano Ronaldo ahead of their Sunday's Premier League game. 

It's been gathered that the Portuguese star has been experiencing discomfort with one of his knees. 

Cristiano Ronaldo hurt his knee while doing his characteristic leap while celebrating the penalty he converted to hand the team a 3-2 win against Arsenal at Old Trafford. 

Cristiano could miss Sunday's visit from Crystal Palace, which happens to be Ralf Rangnick first game in charge of Manchester United as their interim boss.