Textbooks give a lot of emphasis to the case that is, however, the least common: the acute patient with sciatica and neurological signs, who corresponds to the phenotype that I have defined here as “extensor” because he finds at least partial relief with the extension of the lumbar spine. I will deal with this case after the “flexor” patient, who is much more common. I don’t think there are statistics based on this classification. The extensor type might prevail in an emergency room or an orthopaedic clinic because the patient usually presents intense and sudden symptoms. My outpatient experience with several thousand chronic patients suggests that in a physiatric clinic, 95% of the cases arrive in the chronic phase. Therefore, the most common case is from the beginning or has become, over time, of the flexor type. Beware: this means that, given the large numbers typical of this caseload, the extensor patient is also common.