I think its ridiculous to say that since he was injured he's been stealing his paycheck, and that he owed it to the knicks to walk away from the deal.
He was payed for playing basketball, and he was injured playing for the team.
he *may* have owed it to the team to accept a mutually beneficial buyout (ie, the allan houston clause) to free up cap room for the team, but the team "locked him in" to a long term contract to alleviate the risk of player movement, and in doing so exchanged that risk for the possiblity of decreasing productivity (such as through injury).
Why, when he was under contract, should the player be the only one to suffer a fnancial loss due to an injury suffered while performing his contractual duties? I'm sorry, that is why you have contracts.