SPLIT is a prospective quality improvement study, designed to change general practitioners` (GPs) and physiotherapists’ (PTs) low back pain (LBP) practice through the introduction and support of a subgrouping for targeted treatment system for the assessment and management of LBP patients in primary care. This system differs from ‘one-size fits all’ usual practice, as it suggests that GPs should systematically allocate LBP patients to one of the three subgroups according to key modifiable prognostic indicators for chronicity. A subgrouping tool helps guide clinical decision-making about treatment and onward referral. Patients in each subgroup (low, medium or high risk of chronicity) are then managed according to a targeted treatment system of increasing complexity. This is a collaborative initiative amongst the School of Health Care- Instituto Politécnico de Setúbal, Nova Medical School- Universidade Nova de Lisboa and the Health Group Centre group of Arrábida.