MILLWALL physio Bobby Bacic says there was "no clinical justification" for Liam Trotter to have knee surgery at the end of last season.
Trotter went under the knife last week to trim a section of cartilage that had been causing irritation for several months.
But Bacic says three separate MRI scans failed to discover the problem and it was only when the surgeon, who had recently returned from the Lions tour in Australia, opened up the midfielder's knee as a last resort that a "small nick" was found.
Bacic explained: "Towards the end of last season, Liam had an irritation of the knee joint. We had it scanned and it came back clear.
"The knee had improved by the end of last season but we went to see the surgeon anyway and Liam had another scan. There was no swelling, pain and the scan was completely clear.
"The surgeon said the knee was completely okay and, if anything, said we had been a little bit over-cautious by bringing him in. The plan was to let it settle down over the summer.
"There was no clinical justification to do an operation at that stage. If the surgeon had suggested doing something exploratory, we would have said 'no'. Liam has no previous history of knee problems so we would never have rushed into surgery.
"When Liam came back for pre-season, he was straight-line running completely pain-free but the minute he started turning, he felt his knee. On one day there was some noticeable swelling.
"The surgeon was back in the country for a brief window so we were able to fit in another scan, which came back clear again.
"Liam still wasn't happy with his knee so the surgeon suggested using a camera to take a look at it, which we don't really like doing because it involves an invasive procedure.
"He found a tiny little nick in the cartilage which wouldn't have been picked up by the scan, so he trimmed that a little. The whole procedure took 20 minutes to do."
Trotter is expected to be out for six to eight weeks.