How long after getting a cortisone shot should it start working because i got a shot in the knee yesterday and it isn't touching the pain?

Cortisone shot time: Most doctors will inject with both cortisone and a numbing medicine (like novicaine that the dentist uses). This may help remove the pain almost immediately. The cortisone can take several days to "kick in" and often can last as long as 6 weeks or longer. Depends alot on why and where the shot was placed and of course, the initial diagnosis.

Needs new evaluation: If shot did not resolve pain, the issue is more complex or the wrong area was injected or the cause was not addressed.