Madison Square Garden is in need of $850 million in renovations, the arena’s management said, and it may not be able to afford them. Previous estimates had pegged the upgrades at $500 million and the Knicks had secured a $375 million loan to help cover the work last week. The rest was to be covered by inter-company loans and the basketball team’s existing cash flows. Last week’s loan terms stipulate that the arena’s debt can only be six times as large as its cash flow, and it’s already getting close at a 5.33 leverage ratio once the loans are drawn, according to research firm CreditSights. One option for the Knicks is to raise ticket prices. Another is to allow player contracts to expire at the end of this season without picking up the tab for any new sky-high salaries, or to borrow some cash from parent company Cablevision Systems. Still, there is the possibility that the Garden’s renovation project could be even more costly than the $850 million now projected. “The New York City construction project that comes in on budget and on time is as rare as a C train after midnight,” CreditSights quipped.