Suffering from chronic knee pain, but my heart rate remains steady

[MommaHale]

I suffered a knee injury almost two years ago, and finally had exploratory surgery this past may. I had my functional capacity evaluation already and they explained that my heart rate should change with the amount of pain that I'm in. My heart rate was around 80 bpm resting and usually remained steady at 118 bpm. It occasionally went above 130bpm, but usually stayed steady. Although I was in excruciating pain, my heart rate didn't change much. Has anyone else had this type of reaction, and will I fail my FCE because of this? Thank you.