ACL is important ligament of knee which gives anterior stability. ACL is usually injured in twisting injuries of knee, commonly in sports like football, tennis, basketball. Symptoms are pain, swelling, knee joint giving way (instability) during activities. MRI is usually used to diagnose it. X ray is done to look for bony injury/ avulsion fracture. ACL reconstruction is required in treatment of full thickness ACL tear with instability. Nowadays anatomical ACL reconstruction with hamstring tendon graft is preferred treatment.