... or my knees and legs are just getting tired . It 's probably residual from the bike thing last weekend , and the fact that I [ stupidly ] wore the Evil Birks * this past week when I went to get my pedicure . I ' m going to throw them away when I get home . I 'm like Homer Simpson with that week old sandwich . Oh , birkenstocks , I ca n't stay mad at you ... The flight was actually very nice , lots of room and I got a nice amount of knitting done .
According to the above context, answer the following question.
What has led the person to want to throw the birkenstocks away ?


They are bad for their posture and cause their feet to be sore when they wear them