**1. Introduction**

The Anterior Cruciate ligament (ACL) is said to be one of the most important stabilisers of the knee preventing the anterior translation of the tibia over the femur. Injuries to the anterior Cruciate ligament commonly occur during sports and are caused usually by sudden stops or change in direction while running, jumping and landing [1–4]. These injuries are quite disabling and take a significant amount of time to recover and rehabilitate despite the surgery. Moreover, people with these injuries tend to end up with increased articular wear with time and end up with early post-traumatic arthritis even with the best of surgeries [5].

ACL injuries have been increasingly common in elite athletes who have ramifications in terms of contract/scholastic obligations, sponsorships and revenuegenerating potential. Though the number of people returning to sports post ACL reconstruction has increased, most professional sportsperson face challenges of returning to preinjury level and performances expected of them. As most of them, do not return to a high level of performance, many careers have ended or shortened because of ACL injury when compared to those without the injury [6, 7]. Consequently, it's important to identify the risk factors which might lead to an increased probability of ACL injury so that preventive measures can be taken.

Risk factors of ACL injury could be divided into two major categories like intrinsic and extrinsic [8]. Intrinsic factors include those which are innate to the individual and are usually non-modifiable. These include factors such as anatomic factors (Notch parameters, posterior tibial slope, lower extremity alignment etc.), neuromuscular factors, genetic factors, hormonal milieus and cognitive function. Extrinsic factors are those which surround the athlete and may include level and intensity of games or activity, playing surface and environmental conditions, as well as equipment used [9–12]. In this chapter, we have attempted to create a comprehensive yet exhaustive list of the risk factors contributing to ACL injury.
