ACL tears happen when the knee is put at a disadvantaged position while playing or falling from a bike.The most common mechanism is twisting of the knee joint while the foot is fixed firmly on the ground leading to stress on the ACL which finally tears due to excessive forces.In patients who are obese or lead a relatively sedentary lifestyle, minor twisting injury can also cause this injury due to bad mechanics, muscle fatigue/wasting and lack of proprioception in the joint due to lack of training.