I agree that there are no real free agents out there that could help the Knicks, but LJ doesn't have to sit the bench the entire year.
From Larry Coon's site:
If the player is disabled between December 1 and June 30, and the physician determines that the player will be out the entire following season as well, then the team has until October 1 to sign a replacement.
So the Knicks wait until December 1st to have LJ declared injured, and gets the exception to be used before Oct 1st of next year. Hopefully this is what Knick management is doing, and then NBA goes along with it.