I had Community Service 3 years ago after a car accident. I was wearing a back brace.
They worked with me on it. 3 months to do 40 hours. They found a place where the work fit within my 10-lb lifting restriction. Goodwill worked with me on my hours - as I was feeling pain, I would do 2-3 hours at a time, and they were fine with that.
While I sympathize with your pain, you could have explained the situation, shown doctors notes, and they would have worked with you on it.

