It may be a state by state thing, the holding a job opening.
I was on medical leave for a year due to my chronic RSI injury, but after 12 months and I still couldn't return to work ( we did do a "test" and I only made it 3 weeks before pain /symptoms returned) .. I was terminated..

Most employers cannot hold or make a job to fit our imitations, for an unlimited time..

Take time to search out a really good atty, some just go thru the motions to get any % of payout..