[Back pain].

Low back pain created a dramatic increase in sick leave from 1970-95 despite of no pain-relevant biological changes of the back. An update of several disc-related pathologies is presented. Especially discovering the significance of Modic changes and a new muscle-function understanding contribute to a modernized view on pain mechanisms. Generally, traditional treatment modalities have an effect wise sparse influence on natural history over time. Subgroup identification is a central issue in modern research, because the effect of treatment can be very different across such groups.