Will a single MRI of the spine detect a ruptured disc?

Yes. Mri of the spine is the best way to visualize a ruptured disc. Remember "ruptured disc" is a generic term for when the gelatinous center/nucleus of the disc gets squeezed out through an opening in the annulus. A good quality MRI will pick this up. However, some of the findings on an MRI might be more subtle such as a dark disc or an annular tear.