Background: Tibial plateau fracture is an intraarticular injury that can affect the stability of the knee joint and lead to patient disability. The aim of this study was to determine the functional outcome of surgically treated tibial plateau fractures.Methods: In a prospective study, 70 patients (46 males, 24 females) with average age of 38 years (23-54 years), with closed tibial plateau fractures who treated by open reduction and plate fixation was studied in two hospitals in Iran, with a one year follow-up. The functional outcome was evaluated by "Hospital for Specific Surgery (HSS)" and SF-36 scores.Results: The average time to :::union::: was 13 weeks with a mean range of motion of 125 degrees one year after injury. Functional results showed a mean HSS score of 80 points (Range: 19-100). Schatzker type I, II, II, IV fractures showed statistically significant better results compared with Shatzker type V & VI fractures. With regard to SF-36 score 1 year after injury, of eight SF-36 subscales, the results were low in 6 subscales. The majority of patients were able to perform most of the pre-injury daily activities after 1 year. The most important independent factors influencing functional results in this study were age of the patients and fracture type.Conclusion: Functional results after open reduction and internal fixation of tibial plateau fractures seem to be excellent according to HSS score, however overall patients' subjective appraisal was not satisfactory.