Sania Mirza has been ruled out of action for a few weeks. Medical reports of her troublesome right knee indicated "a possible Anterior Cruciate Ligament" injury.

The 20-year old Indian ace, who sustained hyper-extension of the knee during her first round match at the Qatar Open in Doha earlier this week, has laxity of the ACL, the doctor treating her at a local hospital in Hyderabad said.

"The MRI scan of the knee joint indicates a possible ACL injury," Dr. Hariprasad of Apollo Hospitals added.

"Sania was complaining of extreme pain in the knee with swelling and on examination [it was found that] she has laxity of Anterior Cruciate ligament.

"As the joint is painful, she will be examined under anesthesia and then further course of action will be decided."

The full extent of the injury and recovery time would be known only after a complete examination, Hariprasad said.

An athlete who has suffered a simple ACL injury could undergo physiotherapy and return to action within a few weeks.  But in case of an ACL with a tear, it could take anywhere between three and six months, a medical expert said.

"If it is a partial tear, then it could be treated with physiotherapy and other methods. After adequate strengthening of the ligament, the athlete could return to action in about three months," the medical expert said.

"If it is a full tear, then surgery will be needed and it could take at least six months," the expert added.

"It also depends on the nature of sport. If it involves a lot of twisting and turning, then that much strengthening [of the ligament] will be needed."

The ACL is the major stabilizing ligament of the knee. It is located in the centre of the knee joint and runs from the femur (thigh bone) to tibia (shin bone).

Cricketer Yuvraj Singh suffered a similar injury and was put out of action for three months.

Sania, ranked 46th on the WTA Tour, sustained injury during her victory Italy's Romina Oprandi in the opening round of the Qatar Open. She pulled out of the tournament hours before her singles second round.

The Hyderabadi lass, the first Indian to win a WTA Tour title, was scheduled to play at the 2.1-million-dollar Pacific Life Open in California next fortnight.