O.K., this growing old thing (>50)  is a pain...REALLY. I purchased these for my husband who has been complaining of knee pain lately. When I looked at his stance from behind, his one foot is pronating, putting his lower leg out of alignment with his knee. This from a man that is not over weight and in good shape.  When the "grown up" flip flops arrived, he opened the package..."Oh, good, at least these don't LOOK like 'Old Man Sandals'...". He put them on and could immediately feel an improvement. I could SEE an improvement in the alignment of his lower leg and his knee. They must be comfortable because he even wears these around the house. I also purchased a set of the ORTHAHEEL orthotics to put in his workout shoes, which were put to good use right away. I can say the two purchases were worth every penny...and then some. Who knows, this may save him from additional problems and damage to his joints going forward. BTW...I started using Orthaheel inserts in my sport shoes and work boots a year ago...definately improved some of my 'old lady' knee pain issues. My advice; while standing in bare feet, look at your feet/lower legs from behind, or have someone take a photo from behind. If you notice you feet 'rolling' or 'collapsing' toward the middle, Orthaheel may help to re-align your foot AND lower leg with your knee. Hope this helps.