She complained to Hawke's Bay DHB that the misdiagnosis resulted in ACC rejecting her claim for an operation.
"I have been turned from a gym-loving, ballroom/disco dancer, often feeding and running elderly around, a fun-loving great-grandma, with the children staying with me, to a miserable, useless, bent old git, probably not fit for surgery now," she previously told Hawke's Bay Today.
Morgan said she had more than two years "taken away, that's precious time I could have spent with my great-grandchildren".
"I have had many a fall now, because my knee gives way, I have many bruises, and I dread waking up in the morning because the pain makes me scream."
But on Monday, Morgan told Hawke's Bay Today the good news.
"I finally had a face-to-face with the DHB on Thursday last week," she said.
"They gave me a surgery date. I am to have my surgery on July 28, and it has a star next to it which means it is not to be cancelled unless absolutely necessary.
"I am really really happy."