Abstract Background: US of the knee is well-suited for evaluation of disease of the knee, particularly in evaluation of injuries of the quadriceps and patellar tendons, injuries of the MCL and LCL, joint effusions and fluid collections around the knee, and guiding percutaneous interventions. Understanding US technique for complete evaluation of the knee and relevant sonographic anatomy, US appearance of common pathologic conditions, and knowledge of important pitfalls provides another tool for the evaluation of knee pathologic conditions. Although the cornerstones of imaging evaluation of the knee are radiographs and magnetic resonance (MR) imaging, ultrasonography (US) is less expensive than MR imaging, easily available, comparable accuracy, low cost, high spatial resolution, dynamic imaging, guide percutaneous interventions, direct patient contact, ability to compare with the contralateral knee, evaluating patients with contraindications to MR, and correlating the patient's site of pain to the sonographic findings. Aim of Study: To detect the role of high resolution ultra-sonography as a growing and useful diagnostic tool in the assessment of different non-osseus peri-articular knee pathol-ogies compared to MR imaging. Patients and Methods: Observational prospective study. The study conducted in Radiology Department at Ain shams University Hospitals. Form April 2021 till October 2021. Patients referred to radiology department for ultrasonography and MRI examination of the knee joint. Results: This study showed US was 100% sensitive, specific and accurate in detection and anatomical evaluation of the peri articular soft tissue lesions in comparison with MRI and not in correlation with the histopathology. Conclusion: Ultrasonography is safe, cheap and efficient tool in the evaluation of the peri articular non-osseus knee lesions. At this point in time, we concluded that ultrasonog-raphy has an important complementary role with MRI exam-ination in the evaluation of the knee joint different pathologies yet it is operator dependent and needs experience.