The outcomes of surgical treatment are correlated with the nutritional status of patients, both in overweight and underweight situations with loss of muscle mass. Even in patients who are well-fed, inadequate nutritional support in preoperative time is endangering surgical procedures. Nutritional status is defined by a series of interrelated factors and is determined by the synthesis of information collected through different methods. Muscle-mass is decreasing due to inactivity or reduced mobility caused by illness witch leads to limitations in everyday life functions. If the problem is noticed in time, we can prevent unwanted effects or alleviate them at least. Methods for evaluating certain nutritional status constituents are divided into surveys, anthropometric and biochemical methods, and clinical examination. Evaluation of nutritional status and application of various enteral nutrition modalities should enter standard diagnostic and treatment procedures in Croatian hospitals. In this paper attention is paid to the study of the risk of malnutrition in orthopedic surgeons, involving 57 patients from Zagreb and the surrounding area. The research was conducted at the Clinical Hospital Center of Sestre Milosrdnice in the Clinic for Traumatology. The aim of this study was to determine the incidence of malnutrition of orthopedic surgical patients after the surgical procedure of the locomotor system of the lower extremities. Within the study, muscle mass was measured using bioelectric impedance on three occasions. Also was measured the skin fold of the upper arm, back and abdomen, and the circumference of the upper and lower leg. Data on lifestyle and quality of life were also sought, and data from medical records were used. The patients signed a voluntary informed consent to participate in the clinical trial, which was approved by the ethics committee after a thorough analysis of the research proposal and accompanying documentation was provided. Data analysis showed that male patients had a significantly better muscular strength and muscle mass index than female patients, and that younger patients had significantly better nutritional status and higher muscular strength compared to older patients. Data analysis suggests that patients with knee injuries have significantly better nutritional status, better muscle strength and higher muscle mass index than patients with injuries to other lower extremity regions. The aim of this research was to compile guidelines for perioperative nutritional support for various enteral nutrition modalities. Evaluation of nutritional status and application of various enteral nutrition modalities should enter standard diagnostic and treatment procedures in Croatian hospitals.