Answer :
The correct answer to the exception in the Ottawa knee rule indications for an x-ray is age (option a). The rule specifies isolated tenderness of the patella, tenderness at the fibula, and an inability to flex the knee to 90 degrees as indications, but age is not a direct criterion for an x-ray according to the rule.
The Ottawa knee rule provides criteria for when an x-ray of the knee is warranted. To determine the indications for an x-ray assessment for possible knee damage, we consider symptoms such as inability to bear weight immediately after the injury and in the emergency department for four steps, age over 55, isolated tenderness of the patella (with no other bone tenderness of the knee), tenderness at the head of the fibula, and inability to flex the knee to 90 degrees.
Among the options listed in the question, age is the exception to the Ottawa knee rules, whereas the other three options (isolated tenderness of the patella, tenderness at the fibula, and inability to flex knee to 90 degrees) are clear indications according to the rule (option a).
