The team management became suspicious of the injury which led to Akhtar sitting out of third day of the Test in Rawalpindi when he was back on the field to bat on the fourth day without showing any signs of discomfort.
A four-member team of doctors from Shaukat Khanum Memorial cancer hospital in Lahore on Friday said that the 28-year-old ace pacer's injury was due to persistent stress.
Akhtar, known as the Rawalpindi Express, was injured on the second day of the third Test, the decider in the series won by India 2-1.
He had been troubling the Indian batsman with his extreme pace when he fell down on his follow through, hurt his wrist and back, and left the field.
His absence helped India pile up a mammoth total that eventually outclassed Pakistan, who lost the crucial match by an innings and 131 runs.
Pakistan captain Inzamam-ul-Haq lashed out at Akhtar after the defeat saying the fast bowler had let the team down and his attitude had not been up to the mark.
The allegations prompted the Pakistan Cricket Board (PCB) to appoint a medical team to investigate injuries to Akhtar and two other senior players, wicketkeeper Moin Khan and all-rounder Abdul Razzaq, who did not play in the final two Tests due to injuries.
The medical team was expected to submit its report to PCB chairman Shaharyar Khan by next week.
Akhtar, who is due to fly to England next week to play for Durham County, said he would never even think of feigning injury.