The legendary footballer suffered from dementia and had long battled against the illness.
Kinnear's wife, Bonnie, spoke to The Telegraph and The Mirror about his condition back in 2021.
She stated: "He started to get moody - a bit depressed. I thought, 'This isn't right.'"
She then added: "Then he got aggressive in certain situations. It just wasn't Joe. It was a problem trying to get him to see somebody but we eventually got him to a doctor and he was diagnosed in 2015.
"They classed it as early onset vascular dementia and, since then, he has just deteriorated. He's in the late stage. It is heartbreaking to see how someone can change.
"He was larger than life. He loved people. He'd walk in a pub, buy everyone a drink, tell funny stories and be the life and soul of the party."