Newcastle Knights forward Robbie Rochow has successfully undergone surgery on a bulging disc in his lower back.

Rochow hasn’t played a game since he sat out the Knights’ round-four win over Penrith last month after suffering back spasms during the warm-up.

“Awake from my back operation, went well and feeling great. Looking forward to doing my rehab and coming back fitter & stronger! @NRLKnights” tweeted the 24-year-old, who is expected to be sidelined for at least six weeks.