When you ask a question, make sure to include a complete sentence, so we can see the context where the word or phrase appears. That way, we can find the best translation. It's often difficult to translate a frase suelta.
In this case, my best guess is that it is an exclamation, similar to "Jesus Christ!" or "Jesus, Mary and Joseph!" or even "for Pete's sake!" It is not a common phrase, and many Protestants would probably consider it vulgar.
The expression "Christ on a crutch" is a "Southernism", which I have heard a few elderly men use, and would be considered innappropriate and disrespectful by a lot of folks. Church attendance is very high in most parts of the Southern US and even expressions like "Oh God" or "good God" are avoided in many (not all) circles....
The phrase is also the name of a rap-song... Again, the expression is not common outside of the US South and even there is best avoided...
Forgive the late reply, but "Christ on a crutch" is generally an exclamation of despair upon having encountered an unlikely event of profoundly bad luck which was entirely unexpected. Insomuch as Jesus was Himself a faith healer, you would never expect to discover Him walking upon a crutch (as if from a broken leg).
The other replies seem to focus on the phrase as merely a swearword, and perhaps not too much of what we'd call a "minced oath" (e.g. "darn it to heck!"). But I think it is more akin to the exclamations "You have got to be kidding me!" or "This can't possibly be happening!" Christ on a crutch is an exacting analogy of something that "can not possibly be happening."
Yes, It's an exclamation or expression of dismay.
Re: the etymology, I believe that the phrase is much older and English rather than originally from the American South. In his book The Story of English, Robert McCrum details the arrival of Christianity to England and notes that the word cross was used in the North as 'cros' but originally in the South the term 'croc' was used, from the Latin Crux, and he gives as an example the fact that in London there is a street and religious order The Crutched Friars. The crutch pronunciation of cross eventually gave way to the more common word used today.
Royal doesn’t say which American novel, but one famous American novel, which features the phrase in the mouth of the character Captain Queeg, is The Caine Mutiny, by Herman Wouk. Which I just finished reading.
Queeg is of course portrayed quite negatively in the novel, therefore it’s fair to say that his frequent use of this expression might also be interpreted negatively.
Indeed, the expression is repulsive and unduly offensive, and is a step beyond someone simply yelling out “Christ“ in a moment of frustration. It should not be used unless the speaker intends to be deliberately offensive—and not offensive merely to Christians. If I ran across one who consistently used the expression, I’d be warned away.