"Crooks sat on his bunk and looked at the door' for a moment, and then he reached for the liniment bottle. He pulled out his shirt in back, poured a little, liniment in his pink palm and, reaching around, he, fell slowly to rubbing his back."(Steinbeck 84)
I think that Crooks' back could be symbolism for his inner pain and emotions of loneliness and frustration that he has to deal with daily. Him rubbing his back could symbolize how being alone and thinking is his only way of healing or treating that inner pain. However, just as the liniment doesn't fix his back, he will never truly escape that pain fully.