ObjectiveTo evaluate the manifestations and diagnostic value of low-field MRI for all kinds of unusual knee injury after trauma. MethodsWe retrospectively analyzed the MRI data of 385 patients with knee joint injury in our hospital confirmed by arthroscopy and operation between January 2010 and December 2012. The injury with an incidence of equal to or lower than 5% was regarded as unusual injury in this study. Incidence rate of all kinds of unusual injury was counted and MRI imaging findings were analyzed. ResultsAmong the 385 patients, meniscus injury was found in 155 patients, cruciate ligament injury in 117, medial collateral ligament injury in 127, bone contusion in 84, and fracture in 44. Multiple injuries also existed. At the same time, root injury of meniscus was found in 15 (4.0%) of the 385 cases; meniscocapsular separation in 3 cases (0.8%); posterolateral complex injury in 17 cases (4.4%); Segond fracture in 6 (1.6%) cases; femoral plate ligament injury in 1 (0.5%)case; medial patellar retinaculum injury in 19 (4.9%) cases; cartilage fractures in 16 cases (4.2%) in which patellar cartilage fractures occurred in 5 cases (1.3%), femoral and lateral condyle cartilage fractures in 11 cases (2.9%). ConclusionThe low-field MRI has a high accuracy in the diagnosis of knee joint unusual injury, and is an ideal and noninvasive method for knee joint injuries.