Sachin Tendulkar has to make a careful decision on returning to the cricket field since medical tests would not reveal if his tennis elbow has been completely cured or not, a leading biomechanics expert said on Tuesday.

Bruce Elliott, professor of biomechanics with the University of Western Australia, said medical tests would not reveal whether the inflamed tendons of Tendulkar's left elbow were still tender or had gained strength.

"It would be very difficult to know with the MRI scan or other tests if the muscles are tender yet," Elliott, who was among the experts' team that studied Muttiah Muralitharan's action while bowling the 'doosra' recently, said.

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India's batting maestro is racing against time to be fit for the second cricket Test against Australia, starting in Chennai on Thursday. The world's highest run-getter in international cricket has been out of action for the past two months.

Team physiotherapist Andrew Leipus and doctors treating Tendulkar have not given a clear time-frame as to when he would be fit to start playing again.

Elliott, in the city to present lectures and live demonstrations at the 12th International Tennis Federation's Asian regional coaches workshop that was inaugurated today, said Tendulkar should not face a recurrence of the injury or pain if the root cause has been rectified.

"If you have corrected the problem, it should not occur (again)," he said. Elliott said the stretching of the leading elbow muscles in the opposite direction for a brief moment when the bat came in contact with the ball could be the actual reason for the tennis elbow in Tendulkar's case.

"In tennis players, when they play back hand, the elbow is pointed in the direction of the ball. When the racket hits the ball, the muscles are stretched backward sharply before they get back to the direction of the swing," he cited as an example.

Elliott's field of research covers, besides tennis and cricket, kayaking, rowing and running.

He said the highly flexible physique, which was a unique feature of the subcontinent people, has led to its own problems.

"For instance, Shoaib Akhtar has hyper-extension. It is not a deformity, but an individual thing. Muralitharan's elbow is another example," he said.

Talking of level of tolerance for bowlers, Elliott said the ICC must make sure the umpires were able to interpret the rules and the angles (degrees of flexion) was observable.

"There is no point in having a half-degree difference between legal and illegal actions," he said.