The ACL is the primary restraint to anterior tibial displacement. The classic history of an ACL injury begins with a noncontact deceleration, jumping, or cutting action. The knee is been hyperextended or popping out of joint and then reducing. The knee swells, and aspiration of the joint reveals hemarthrosis The Lachman test is the most sensitive test for anterior tibial displacement (95% sensitivity).Sequelae after ACL injury include quadriceps weakness, Occult osteochondral lesions, Rotational laxity, meniscus injury,There is also the risk of more tears occurring with time, Knee dynamic instability, Regional bone density changes,Knee osteoarthritis especially patello-femoral. Early management According to quality of life , symptoms,degree of activity. Graft options are hamstring tendon,patellar tendon. Early rehabilitation and pysiotherapy reduce laxity in non athletes. Early reconstruction reduces incidence of osteoarthritis. Menisectomy for meniscal injury may be indicated.