Background: Swelling and discomfort in acute knee injuries make knee clinical tests challenging and ineffective. Magnetic Resonance Imaging (MRI) could also be used to diagnose intra-articular and extra-articular traumatic lesions in the knee while Arthroscopy was the traditional gold diagnostic method for evaluating intra-articular knee injury. We proposed the study to evaluate the effectiveness of MRI in assessing the Anterior Cruciate Ligament injury in comparison to arthroscopy of the knee. Method: Study was undertaken in the Department of Orthopaedics, Datta Meghe Hospital, Nagpur in collaboration with Datta Meghe Hospital, Sawangi, India from August 2019 to March 2020 to ascertain the need for routine MRI of the knee for assessment of an injury of the anterior cruciate ligament in sudden traumatic haemarthrosis. 16 yrs to 60 yrs age were included and intra-articular fractures, patellar dislocations, extraarticular ligamentous lesion, previous injury to the same joint, non-haemorrhagic, and haemophilias were excluded. Results: 32 cases of acute traumatic haemarthrosis of the knee during the period from August 2019 to March 2020 were subjected to MRI examination and arthroscopic examination and findings noted on the scoring system based on The International Knee Documentation Committee (IKDC) 2000 scoring system. Total MRI positive ACL deficient patients were 18 out of 32 and total Arthroscopically positive ACL deficient patients were 13. 10 patients were ACL deficient both in MRI and Arthroscopically and 11 were having normal ACL both in MRI and Arthroscopic evaluation. Fisher exact test p= 0.0751 and Chi-square with Yates correction p= 0.1125. The sensitivity of MRI in detecting ACL injury is 76.92 in comparison to arthroscopy. In spite of the high sensitivity, the specificity of 57.89 shows there is a decreased probability of detecting true negatives. The positive predictive value is 55.55 and the negative predictive value is 78.51 with an accuracy of 65.62. Conclusion: The cost of MRI although reduced is significant in comparison to arthroscopy. MRI with a sensitivity of 76.92 has a high index of detecting true positives. The probability of detecting true negatives is low with high false negatives. Arthroscopy examination is superior to MRI in detecting ACL injuries from the comparison with significant P-value.