Medicare Advantage plan denied my moms knee replacement

My mom is 71 and needs a knee replacement. Her orthopedic surgeon submitted the prior auth to her Medicare Advantage plan and they denied it saying she hasnt exhausted "conservative treatment options."

She has done physical therapy, cortisone shots, anti-inflammatory medications, and a gel injection. Over 18 months. Her surgeon says theres literally nothing left to try and the joint is bone on bone.

We appealed and got denied again. Now filing an external review. The whole thing feels designed to delay until people give up. She can barely walk and theyre telling her to try more PT.

Anyone dealt with Medicare Advantage denials? Do the external reviews actually work?