A work-related orientation within medical rehabilitation represents concepts with a stronger focus on the patient's individual vocational requirements and is based on different vocationally-orientated strategies of treatment. "Medical Occupational Orientation" ("Medizinisch-berufliche Orientierung", MBO), the model of Klinik Niedersachsen in Bad Nenndorf, places Functional Capacity Evaluation according to Susan Isernhagen (EFL) at the centre of rehabilitation diagnostics and therapy. This study investigates the effects of the MBO model relative to activities and vocational participation of patients with musculoskeletal disorders faced with vocational problems and on management at the interface between medical and vocational rehabilitation. Presented are findings of a randomized follow-up study aimed at evaluating the MBO model. A total of 494 patients of LVA Westfalen, a regional insurance agency, took part. A need for MBO was diagnosed for 222 patients. These patients were randomly assigned either to the MBO model of treatment (experimental group --> U[+]) or to the conventional medical treatment (control group --> K[+]). Patients without a need for MBO (U[-], K[-]) were treated likewise. The written questionings took place at the beginning (t (1)) and end of rehabilitation (t (2)), as well as six (t (3)) and twelve months (t (4)) after the patients' discharge. Currently, the results are based on the 6-month follow-up. Concerning the activities, an MBO-related effect in the experimental group (U[+]) has been found for the Pain Disability Index (PDI), effect sizes being d (u+) = 0.82; d (k+) = 0.17. The risk of unemployment six months after rehabilitation is decreased for MBO(+) patients who participated in the MBO model. In addition, the clinic can make effective prognosis concerning subsequent participation in vocational rehabilitation for both experimental groups (U[+], U[-]). Established for the first time in a randomized controlled trial, the findings presented show that patients with musculoskeletal disorders who are faced with particular vocational problems will achieve significantly better results concerning activities and vocational reintegration if their medical rehabilitation had been based upon an EFL-centred MBO approach.