The ACL (anterior cruciate ligament), is one of the four ligaments of the knee, these four ligaments join the tibia (big shin bone) and fibula (smaller shin bone) to the femur (thigh bone). These four ligaments are prone to injury if the knee joint is over-exerted, twisted, or overextended. Women pose five times greater risk of injuring their ACL than do men.
Injury to the ACL can be either a partial tear (which is a minor injury where the ligament is not severed but sustains a tear only part of the way into it), or a rupture (which is a serious injury where the ligament is torn completely through). While a partial tear can usually be treated with a few months of physical therapy and use of a brace; generally a ruptured ACL requires surgery to replace the severed ligament with a donor ligament taken from another part of the body as the ligament cannot be sutured back together and no other type of tissue can replace it.
There are several ways the ACL can become injured. These are the five most common ACL injuries that may occur.
• Twisting injury: this type of ACL injury occurs often in athletes, especially basketball players, although many different sports can produce events that can cause this injury. The injury occurs when the knee is twisted violently while pivoting or twisting. Basketball players are especially prone to this type of injury due to their shoes gripping the floor and turning and changing direction rapidly while playing.
• Bad landings: many different types of sports require jumping, and when you jump you are going to land. If you land poorly (bad landing) the end result could be an ACL injury. Again, basketball players are prone to this method of injuring an ACL, but there are many sports that can lead to this type of ACL injury. Skydiving, skateboarding, hurdles, parkour (aka free running), high jump, gymnastics, volleyball, and many other sporting activities involving jumping can lead to a bad landing, which In turn can
lead to a torn ACL.
• Hyper-extending: hyper-extending is when the joint is extended beyond its normal range of motion. A hyper-extended joint can occur during many types of athletic activities and is when the limb, in this case the leg, is bent backwards as it were. The knee is designed to flex (bend) in only one direction and then extend until the leg is straight. If the knee is bent in the opposite direction it is designed to do so this is called hyper extension. This type of injury is very painful and can result in a serious ACL injury including a full rupture.
• Sudden stop/deceleration: another method of injuring the ACL is suddenly stopping with a firm grip on the ground/floor with the foot. This can injure the ACL because when you stop abruptly the lower leg stops, but from the knee up the rest of your body is still in motion from inertia. So the knee joint is moved in a manner in which it was not designed to do and so this often results in an ACL injury. This usually does not result in a full rupture but can cause a partial tear.
• Number five is contact injury: contact injuries occur in football, soccer, and rugby often but can occur in other sports and also can occur by other means. Automobile and motorcycle accidents often result in this type of ACL injury. Contact ACL injuries are the result (most often) of the knee being struck from the side (big tackles or swift kicks) while the foot is firmly rooted, it is estimated that about 20% of ACL injuries are contact injuries while the other 80% percent are non-contact related.
While these top five causes of ACL injury may be the most common, there are still other methods of ACL injury; one of which is merely age and over use. Even the simple act of walking down the stairs could cause an ACL injury if you step or twist in a wrong way. Often it is advisable to wear knee braces as a preventive measure while performing strenuous athletic activities to lower the chances of an ACL injury.