Brian Allens knee Injury

We have a longtime Friend of our Family that played in the NFL on the OL he had made All Pro and was a Pro Bowl player but injured his knee and it was a nagging injury that forced him to retire.
I don't know the extent of Brian Allen's Knee injury, but they are usually not good especially for Lineman because of the twisting and turning and extreme loads put on them in the trenches or what they like to call it the Pit. Of course, many have continued on. GO RAMS!