Background: Open knee joint injury is a deep traumatic laceration violating the joint capsule. It commonly occurred in males and the commonest causes are road traffic accidents and gunshot injuries. Associated injuries like periarticular fractures are common and lead to poor outcomes. Open knee joint injury needs urgent surgical debridement to prevent risk of septic arthritis and limitation of movement to the knee joint. Objective: To asses’ treatment outcomes and associated factors of open knee joint injury among trauma patients visiting TibebeGhion specialized Hospital, North West Ethiopia, 2020 Methods: Institutional based retrospective cohort study was done by reviewing medical records of patients treated for open knee joint injury from January 2019 to July 2020. A total of 43 patient’s medical records was reviewed as study sample size giving 86% response rate. Data was entered and exported by using Epi Data manager version 4.4.1 and was analyzed by using, SPSS version 25. Findings were presented by using tables and texts. Chi-squared test was conducted and p value less than 0.05 were considered significant. Results: Fourteen (32.5%) of this study participants had developed either infection, limited range of motion to the joint on follow-up due to open knee joint injury. Majority of the injuries (58.1%) were caused by road traffic accident. Presence of associated injury to the joint, wound size, time of wound closure, need for redebridement and diagnosis method showed significant association with poor outcome. From the diagnosed infection 90% was septic arthritis. On follow up 8 patients (18.6%) developed limited range of motion to the knee joint. Conclusion: The rate of complication as one outcome among open knee injury patient in the study area was significantly higher. Presence of associated injury, wound size, time of wound closure, need for redebridemnt and diagnosis method were showed significant association with complication outcome. Routine public education campaigns should be conducted to create awareness about road traffic accidents and treating open knee joint injuries on emergent bases should be continued. Key words Trauma, open knee Joint, injury, Ethiopia