Well, a herniated disc or "slipped disc" is when an intervertebral disc, (the cushions that sit between each vertebra of our spine) may slip out of place or rupture. If pressing on a nerve this may cause severe pain.
(Addendum to question due to lack of space in title): Example -- A near fall and deep bruise to leg in a hospital recovery room shortly after a microdiscectomy for herniated disc, due to a defective arm on recliner chair (actually there were 2 incidents involving defective recliner chairs). Weeks later, MRI showed a re-herniation of the disc. Would the reherniation (injury) be considered intrinsic or extrinsic?