The 30-year-old full-back damaged ligaments in his knee during the away game at Middlesbrough last September and despite one re-appearance in the FA Cup tie at Fulham in January he has been sidelined ever since.
Grainger was one of the eight first-team players that reported back ahead of most of the squad for training at Wast Hills earlier this week but tendonitis in the knee has halted his pre-season schedule.
The Blues left-back is expected to recover from this latest bout of surgery in about a months time.
