The doctors said it would be "impossible" for Khan to travel to Mianwali town, where he is registered as a voter.
Shaukat Khanum Hospital chief executive Faisal Sultan too said Khan could not be discharged before the May 11 general election because of his injuries.
A decision on discharging Khan will be made only after conducting some more tests, Sultan said.
"The most important for a person with such injuries is that he should remain immobile," he said.
Doctors expect the 60-year-old Khan to make a full recovery but are not sure how long he will have to remain in hospital.
The May 11 general elections mark a historic milestone for Pakistan as one civilian government completes its term and prepares to hand off to another.