Torn Anterior Cruciate Ligament (ACL)

A torn Anterior Cruiciate Ligament (typically shortened to ACL) is a debilitating injury to the knee. ACL injuries can be mild, such as a small tear, or severe, such as when part of the bone and the ligament separate from the rest of the bone or when the ligament tears entirely. Torn ACLs often occur during high impact sports where abrupt stops from high speeds occur, or when the knee is forced to make a sharp change in movement. They are common in American football, alpine skiing, rugby and basketball. When an ACL injury occurs, the person may experience a piercing “popping” sound. Following this, severe pain occurs making it impossible to continue playing. There may be a feeling of instability when bearing weight and the knee will begin to swell up immediately. Continuing to play a sport after suffering an ACL injury can lead to devastating consequences, and it needs to be treated immediately.


Ligaments are strong bands of tissue which connect bones to each other. The ACL connects your shinbone to your thighbone and helps stabilize your knee joint. An ACL tear occurs when an athlete decelerates rapidly and then makes a sudden change in direction or sharp turn. It can also be caused after landing awkwardly from a jump, from a fall (such as during downhill skiing), or from a tackle in football (somebody tackling or landing on your knee while it is locked or hyper-extended). Most ACL injuries however, occur without contact. Women are more prone to ACL injuries than men, especially women who play tennis, basketball, and volleyball. This is due to general muscular strength, differences in anatomy between women and men, and the reaction time of muscle coordination and contraction. The Encyclopedia of Sports Medicine and Science has more information about the causes of ACL tears.


When an ACL injury occurs, it is important to reduce swelling and pain in your knee. You should rest your knee and put ice on it, and use an elastic bandage to give your knee a gentle compression. You should also elevate it, ensuring it is propped up above the level of your heart. You may need to walk with crutches, and take pain medication to help alleviate some of the pain. It is important to see your doctor as soon as possible. Together, you can decide if you only require rehabilitation or if surgery is necessary. Athletes who want to return to sports involving jumping, pivoting, and cutting generally pursue surgery. Unfortunately, it is not possible to sew a torn ACL back together. Instead, the ligament is swapped with a section of tendon from anther part of your leg or knee (called an autograft). Small incisions are made around your knee joint during surgery, and the placement of the ACL graft is guided by a fiber-optic viewing scope.


The primary objectives of rehabilitation after ACL surgery are: maintenance of the psychological well being and aerobic conditioning, provision of dynamic and static stability, restoration of joint anatomy, and early return to sport and work. The following is an example of a rehabilitation program. The first two weeks of therapy are designed to decrease swelling and pain while increasing the range of motion in the knee. Weeks 2-6 place an emphasis on increasing weight bearing while still increasing the range of motion in the knee, and also gaining quadriceps and hamstring control. The third stage (weeks 6-12) looks to improve muscular control and strengthen the muscles. Finally, the final phase (12 weeks to 6 months) involves the gradual introduction of sports exercises aimed at improving reaction times and agility and increasing total leg strength. For most athletes, recovery time is between 6 and 9 months. While an ACL tear is not entirely preventable, there are things you can do to decrease the risk, such as strengthening your hamstrings, improving your conditioning, wearing proper equipment, and learn proper landing techniques if your sport involves jumping.