Knapp participated in 1999, at the age of twenty-six, in the third season of the reality program and then became a well-known face for TV viewers.
According to Andreas Johnson, Lisa Knapp had an underlying connective tissue disease and died due to a ruptured aorta.
"According to the responsible doctor, it was nothing that was triggered by external circumstances. There was nothing that either she or we could have done differently. It still feels like a nightmare, and we are trying to understand what cannot be understood", he writes.
The singer has previously told about periods when his wife was seriously ill, she was diagnosed in 2011 - the same year the couple got married. They met in 2004 and have two children together.
Lisa Knapp became 52 years old.
