Baseball

Play at first base. No one with that type of injury should have to stoop down on their knees for inning after inning.

He could really hit but the only way he'll keep his status as a pro baseball player for several years as opposed to several months is if he can remain off his knees for long periods of time.

I say this as someone with twenty years as a home health aide, countless friends who do physical therapy, etc. And a husband who still babies on knee on account of football injuries from HS.