Antonio McDyess’ left knee goes under the knife for the third time in 18 months today at the Mayo Clinic in Rochester, Minn. The viability of the Knicks’ future hangs in the balance.

The bone-graft surgery, which the Knicks contend will expedite McDyess’ slow-healing patella bone, could take anywhere from 25 minutes to two hours. The surgery time depends on how much bone graft McDyess’ knee needs.

Knicks GM Scott Layden, team doctor Norman Scott, McDyess and McDyess’ agent Andy Miller flew to Minnesota yesterday.

McDyess received a second opinion from the Mayo Clinic after Dr. Scott decided last Wednesday’s CAT-Scan showed McDyess needed more surgery. Mayo Clinic’s Dr. Michael Stuart, one of the nation’s premier bone-graft specialists, will perform the surgery. Dr. Scott will assist.

The Knicks are still hopeful McDyess could be ready for training camp, though his history of slow healing puts that in doubt. There’s a chance he could miss the start of the season and there must be concern McDyess’ left knee is falling apart from wear and tear.

Another CAT-Scan could be taken as soon as three months – mid-July – after which, if the patella bone’s healing is complete, he could be declared ready to play.

However, the Knicks never expected, on the six-month anniversary of his October surgery, that the cracked patella bone would not be fully healed. “This will involve more bone graft into the area of the fracture to enhance the biology of the fracture healing because it’s been healing very slowly,” Dr. Scott said. “If it’s left now, it’s weak. But it’s not a situation where once it’s fully healed, we have to be concerned about it.”

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