Background The prevalence of diabetes mellitus (DM) or malnutrition in hospitalised patients depends on the clinical discipline, but is much higher than in the normal population. In orthopedic trauma surgery, this increase is frequently associated with more postoperative complications and constantly rising costs. In addition, the quality of life of this target group is decreased, but literature ist rare. Therefore, we aim to analyse the factors influencing the postoperative complication rate as well as the quality of life of orthopaedic and trauma patients.Methods Within this prospective trial in the period of 06/2014 to 02/2017, we analysed data of 1643 patients from traumatology - geriatric and septic traumatology - as well as endoprosthetics with regard to the clinical outcome, the complication rate and the quality of life (Short Form Health Survey 36, SF-36) associated with diabetes mellitus (DM) and the nutritional status (Nutritional Risk Screening 2002, NRS).Results Within our hospitalised group of trauma patients, the prevalence of diabetes mellitus was 12.4% and the risk for malnutrition (NRS >= 3) was 18.3%, which is much higher than in the normal population (DM 7.2%). Patients suffering from diabetes mellitus had significantly more complications than patients without diabetes mellitus. Similar results were found when comparing patients with a risk of malnutrition to the patients without. Furthermore, patients with DM evaluate their subjective quality of life lower than do patients without DM in the most domains of the SF-36, especially in the subjective-physical domains, while patients with NRS >= 3 assess their quality of life as being lower than do patients without a risk of malnutrition in all domains of the SF-36 (physical and mental). Additionally, we showed that reduced nutritional status has a greater influence on the decline in quality of life than did diabetes mellitus.Conclusion Both diabetes mellitus and malnutrition seem to influence the subjective quality of life and the complication rate of hospitalised trauma patients. A nationwide data collection and targeted interventions within the frame of interdisciplinary cooperation are necessary. In this way, the postoperative complication rate as well as associated higher treatment costs could be reduced.