Thomas' surgery, first reported by the Newark Star-Ledger, took place earlier this week to repair a partial tear. Thomas' season was already finished after the Giants placed on him on season-ending injured reserve Aug. 31, when the team reduced its roster to 53 players.
Thomas had been sidelined since early in training camp after he "aggravated" his surgically repaired ACL when he slipped while trying to cover Domenik Hixon.
Thomas consulted with three doctors and the consensus was that he could rehab in hopes of playing again this season. But the Giants ended up placing Thomas on season-ending IR, opting not to use their temporary IR spot on him.
According to the Star-Ledger, Thomas recently underwent a scope on his knee that revealed a partial tear. He then underwent surgery, performed by Dr. James Andrews.
Thomas tore his right ACL during the 2011 preseason and missed all of last season. He first tore his right ACL while at USC.