New date of injury for an open claim?

[ProbationRachel]

I am a probation officer in Sacramento, CA and was injured 2/28/2008 during a work training. There was no question of my injury being work related. My wrist, elbow, and shoulder were all affected. I went back to work immediately on light duty and worked that way until 4/1/2009 when I returned to work with no restrictions. In July of 2009 I was laid off. I then had wrist surgery in August of 2009 and collected worker's compensation checks for 3 months during recovery. I was then again released to full duty in December 2009.

On March of 2010 I attended a work training (I still work on-call) and my shoulder was very sore afterwards. My shoulder always gets sore after physical trainings since the initial injury. I mentioned that it seemed to be getting worse to my doctor during my last check up and he has since ordered an MRI and talked about me having shoulder surgery.

Today I received a call from him stating that he thinks I might have to receive a new date of injury for the shoulder because it had been steady for awhile and then suddenly got worse.

My question is - Can they make me file a new claim even though my other claim is still open and I have not been found permanent and stationary? The pain in my shoulder is exactly the same place it was before, only worse now. I am concerned about the idea of a new claim as I was employed full time during the initial injury date and now only work on-call and so the difference in worker's compensation pay is huge.