Dr. Heinz Buhlmann, who is treating Hingis in Zurich, has put the former world number one through a series of tests this week to assess damage to her left foot and heel and her left knee and hip joints, her agents said Friday.

The test results are expected back this weekend and only then will Hingis know whether Buhlmann's initial fears that the Swiss could be forced to retire are proved correct.

A statement on Hingis's condition is expected from her management company Octagon Sunday or Monday.

The problems have forced Hingis to pull out of tournaments in Berlin and Rome during the last fortnight and her Swiss manager Mario Widmer has already said that she is "80 percent likely to miss the French Open."

According to Octagon, Hingis has a long term problem with the heel, ligaments and tissues in her left foot.

They have refused to speculate on how serious the damage is until the test results are known.

Buhlmann has warned that long term inflammation could have led to joint damage, which may force Hingis to end her career.