Anterior cruciate ligament is important ligament which stabilizes Knee joint anteriorly. ACL is usually injured in twisting injuries of knee, commonly in sports like football, tennis, basketball. Symptoms Pain Swelling Instability – it s feeling of knee giving way or coming out during activities Many times it is associated with meniscus or collateral ligament injuries. Diagnosis MRI – it’s a investigation of choice in diagnosing ACL tear. X ray – Since ACL is soft tissue structure, it is not seen in X- ray. However X ray rules out injury or avulsion. Diagnostic arthroscopy – after the easy availability of MRI, role of diagnostic arthroscopy has decreased over years.