A crew was sent to Medieval Madness in Battlefield Enterprise Park, Shrewsbury, on Tuesday afternoon to help.
The female casualty, whose age could not be given by the fire service, had to be helped down before she was tended to by paramedics.
A Shropshire Fire and Rescue Service spokeswoman said: "At 4.44pm on Tuesday, March 7, SFRS Fire Control received a call reporting an incident in Shrewsbury. Request from Ambulance to assist at incident involving female with dislocated knee."
One fire engine was mobilised from Shrewsbury.
West Midlands Ambulance Service has been contacted for an update.