The Green Bay Packers will perform an MRI on star wide receiver Jordy Nelson.  Dr. Carole Vetter from Froedtert & the Medical College of Wisconsin says that's one of many tests Nelson will undergo.  

The injury happened as he landed after catching a pass in Sunday's game against the Pittsburgh Steelers.  It was a non contact injury - no one hit Nelson, he simply went down after turning up field.

Nelson ran off the field - which Dr. Vetter says is pretty normal since the real pain doesn't set in until the knee starts to swell. 

But these injuries can happen to anyone - even the best athletes at the top of their game like Nelson.

\"It's really the way you land from a jump,\" Dr. Vetter said Monday.  \"If your body is in a certain position, gravity and your muscles take over and they call it the point of no return and you're in that position and it's at risk. The ligament is at risk based on landing in that awkward position which you can see on his video for sure on the way he landed and the knee shifting.\"

The Packers will likely release more information soon.  The next media availability is Tuesday morning.