"We sent the MRI scan report to a South African expert and it brought bad news for Akhtar. Since he doesn't fulfill the fitness demands of a fast bowler, he may miss the best part of England tour," Pakistan Cricket Board spokesman Abbas Zaidi told AFP.
Akhtar has been told not to bowl for the next three weeks, he said.
"The national selection committee will decide how and when to send Akhtar on the England tour when they meet on Thursday," Zaidi said.
"Its an old injury Akhtar sustained last year and surprisingly it did not heal," coach Bob Woolmer told AFP.
Akhtar has not played international cricket since January following surgery on both knees in Australia.
His eight-year career has been plagued by injuries, but after getting 17 wickets in Pakistans 2-0 win against England on home soil last year, there were hopes his career had resurrected.
But he broke down after playing the final Test against India in January this year which forced him to miss the following one-day series and the tour of Sri Lanka in March.
The latest injury was a major setback for Akhtar, and captain Inzamam-ul Haq on Tuesday said he would not permit Akhtar rushed into international cricket as Pakistan need the paceman for next years World Cup.
Pakistan begin the tour with a four-day match against England A at Canterbury before beginning the first of four Tests at Lord's on 13 July. The Tests will be followed by a Twenty20 match and five One-day internationals.