I remember when my father tore his. Even though the tendon is in the ankle his cast went all the way up his thigh. Walking was very difficult for him. Simple tasks got really difficult for him. I remember once he asked me to change my sister's diaper which I had never done before. When he picked her up the diaper fell off. lol
Anyway, when is the concert? I'd have to think he'll back out. Even sitting can be hard if he still has his cast on. He can't bend his leg and will have to have to sit with it stretched out in front of him. They usually have stools in concerts which have no back support. I have to think that would be very uncomfortable for him.
"All our dreams can come true -- if we have the courage to pursue them." -- Walt Disney
We must have different Gods. My God said "do to others what you would have them do to you". Your God seems to have said "My Way or the Highway".