It's NOT YOUR JOB to make up job descriptions. They company HAS to give job descriptions and what that entails like lifting , how many pounds, how many hours a day , over your head lifting, pushing, pulling. They just don't wanna do the work.
Sounds like you have a repetitive motion trauma. It's a normal thing to happen when you stay at a certain job for a long time. It happens a lot where I work.

The Dr. can only tell them how much if any you can lift and for how long. He can't make up job descriptions either. That guy is a jerk you are talking to!

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