There are a number of components going into the decision as to when it safe to return to driving.  First of all, whether your procedure involves your driving leg, and whether or not you have an automatic or a manual transmission.  In addition to the functional ability to break in time there is also the concern of medication effect on reaction time.  We would never recommend returning to driving while taking narcotics.  Beyond the narcotics question the other issues are how quickly you can move your foot from the gas to the brake and then how forcefully you can press the brake.  Studies have shown that the force of depressing the brake pedal is probably the most important factor in returning to safe driving.  In general, my advice is to sit in the driveway and pretend a child just ran out into the street in front of you If you can quickly get from the gas to the brake and slam it on hard you are probably ready to drive that said there have been a number of studies looking at this question.  On average it is safe to return to driving 4 weeks after a right knee replacement and 2 weeks after a left knee replacement.  In general patients can return to driving after a right hip replacement a week or 2 earlier than a right knee replacement.  Operative repair of an ankle fracture or Achilles tendon repair often results in 6 to 9 weeks postoperatively with inability to drive.  Typically, you want to wait at least 2 weeks after coming out of a cast before driving.  ACL reconstruction is similar to a knee replacement; it oftentimes takes 4 to 6 weeks after surgery for a right knee ACL reconstruction.

There are many other factors that play a role in safe returning to driving after an orthopedic surgery.  For example, medication side effects and preoperative function.  If he were slow to push the brake preoperatively, it will take that much longer to recover postoperatively. Please sit in the driveway and slam the break a few times to assess how competently you can break before you try driving.