Mears has been told that 'there is a significant potential risk of developing further complications if he continues to perform the prolonged strenuous exercises required to be an elite rugby player' and he has therefore had bring an end to his playing days despite only recently signing a new two-year contract with Bath.
"This is not how I saw it ending but I feel enormously proud to have played for Bath so many times," said Mears, who made 268 senior appearances for the West Country outfit over 16 years at The Rec.
"This will be a tough period, but the memories I have and the friends I have made over the years will be of huge support. Thank you to the Club and to the supporters, I've loved every minute."
The news comes eight months after Mears stepped down from the England set up and four years after he won a Test cap on the 2009 Lions tour of South Africa.
Mears started the first international for Britain and Ireland's elite against the Springboks in Durban and played five times in total on tour, scoring a try in the comprehensive win over the Sharks at the ABSA Stadium.
Hugely respected by those around him and always a pleasure to interview or chat to, Mears was an immensely popular member of the Bath squad and had been hoping to remain a key figure in their push for bigger things after committing himself to the Club until the 2014/15 campaign in December.
"Mearsy is a legend, pure and simple," said Bath head coach Gary Gold.
"His retirement will be felt by all of us at the Club, and also by the supporters who have cheered him on over the years.
"The only thing that matters is that he is healthy, and if that means he stops playing, then that's the way it has to be. He will be missed, but we will always welcome him back with open arms. This is his Club, and it always will be."
Those sentiments were echoed by former Bath team-mate and now the Rugby Players' Association rugby director David Barnes who played in the front row with Mears on seemingly endless occasions.
"Mearsy is the type of player you can build a squad around - he has been a central figure in the dressing room for years and has shown outstanding footballing skills during his career as well as a physicality belying his stature," added Barnes.