Doctors have advised Akhtar to have scans to reveal the extent of the injury to the left knee, which was operated on, along with the right knee, in February last year.
"I am devastated at the thought of missing the World Cup," Akhtar told AFP, just a month away from the start of the World Cup in the West Indies, which kicks off with Pakistan playing the hosts on March 13.
"I was excited at the prospect of playing the World Cup. I want to help my team win the World Cup and I hope this injury is not worse and I am able to play some part in Pakistan's cup campaign."
His selection in the squad was also subject to his clearing a doping test to be carried out on February 16. Akhtar tested positive for banned steroids in October last year.
If scans reveal serious injury then Akhtar will have to fly to Australia for an operation and it could rule him out of the World Cup.
The latest injury scare to Akhtar compounds Pakistan's problems as they are already grappling with injury worries to key pacemen Umar Gul (ankle), Shabbir Ahmed (hamstring) and Mohammad Sami (back).
To add to their problems, the International Cricket Council (ICC) turned down Pakistan's request for an extension to the February 13 deadline for naming their World Cup squad.
Pakistan Cricket Board (PCB) director of operations Salim Altaf said on Saturday they had made a second request to the ICC as it would be difficult to name the squad without finding out the extent of the injuries.
If the second request is also rejected, Pakistan would name their squad either on Monday or Tuesday, Altaf said.
The 31-year-old Akhtar has been beset by injury. He was forced to return home from Pakistan's tour of South Africa after tearing his hamstring following his 4-36 on the first day of the second Test at Port Elizabeth last month.
Akhtar, nicknamed the Rawalpindi Express, missed the best part of last year due to injuries. He missed Pakistan's tour of Sri Lanka and the Test series in England.
Akhtar only returned for the one-day series against England, starting in August last year, but two months later he and fellow paceman Mohammad Asif were called back from India after both tested positive for the banned steroid nandrolone.
Akhtar was banned for two years and Asif for one year on doping charges in November but a month later their bans were controversially overturned on appeal.
The World Anti-Doping Agency (WADA) has filed an appeal against the overturning of the ban in the Court of Arbitration for Sport (CAS) in Switzerland, which is not expected to hear the case until April this year.