She eventually realized that alcohol had become a 'crutch'. [=that she was drinking too much alcohol as a way of dealing with her problems]
I was 'on crutches' [=I was using crutches to walk] for six weeks after I broke my leg.
He's able to walk short distances with 'crutches' but prefers his wheelchair.
(..) Not bad. They're way ahead out there. You know what I mean? California. I tell them to get out of the f$cking cab. One time I saw a cop chasing this guy with one leg. He was on crutches. The cop? No, the dude that he was chasing. F$cking cops, they chase anything. The man is loaded. (..)1976 Taxi Driver