Sportsmail understands that Stamford Bridge medics sought advice from experts in France to explain swelling in the Russia star's right knee.
Mystery: Zhirkov is been dogged by a knee injury
The frustrated 26-year-old, who moved from CKSA Moscow for £18million in the summer, was even told a change in diet and climate could be to blame.
Zhirkov hurt his right knee on Chelsea's pre-season tour of America and was subsequently told it was a compound injury that had built up during his time at CSKA Moscow.
The winger suffered a further setback when playing for his country against Germany earlier this month and then complained of swelling after playing just 20 minutes as a second-half substitute against Atletico Madrid last week.
'I suffered a painful blow on the knee early in the game against Germany,' he said.
'It ached a little afterwards, but there was no sign of a continuing problem.
'After the match with Atletico, the knee swelled up terribly and the doctors couldn't explain exactly what was happening.
'There was even a theory that my body was reacting to a complete change in climate, food and every else.
Putting it all behind him: Yuri Zhirkov celebrates with his Chelsea team-mates
'There was talk of an operation, but now, after pumping out liquid on the knee, it is more or less normal, thank God.'
Zhirkov hopes to be training again by the end of the week but is unlikely to be in contention to face Bolton on Saturday.
He is yet to make his Premier League debut and has played just 80 minutes for Chelsea, earning his only start in the Carling Cup against QPR last month.
Chelsea will boost their physio team in the new year with the appointment of Reading's John Fearn, who joined the Royals from West Ham United in 2001.
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