ACL Injury

What is an Anterior Cruciate Ligament Injury?

The anterior cruciate ligament is a major and important ligament in the knee that is commonly injured. Treatment depends on the age of the patient, the exact nature of the injury, the nature of any associated injuries, the lifestyle of the patient and their future sporting aspirations. In those patients who are willing to alter their lifestyle a rehabilitation program may be adequate but for the keen athlete who wishes to return to twisting and turning sports, a reconstruction may be the better alternative. In general 90% of those undergoing reconstruction will be able to return to their previous sport and more than 80% will be able to compete at their previous level.

Nowadays, an ability to return to sport at the pre-injury level is rarely due to loss of the ACL. Rather, it is more commonly due to irreparable damage that has been caused to other parts of the knee at the time of the initial injury or in subsequent injuries. It is known that early reconstruction with intact menisci and articular cartilage has a better long-term outcome than late reconstruction, when repeated episodes of instability have damaged these structures.


Injuries to the ACL occur most often in athletic activities (especially twisting and turning sports, such as soccer or skiing) but may be ruptured in work injuries and non-athletic activities. Injury often occurs without contact and is usually associated with a sudden change in direction or a sudden change in speed. It may also occur with the body falling over a fixed leg or with a hyper-extension injury to the knee.

The athlete often describes the incident “My knee went one way and my body went the other”. When the injury occurs, the individual will often hear a ‘pop’ or ‘snap’ or experience the sensation of tearing inside the knee. The knee then swells a great deal within minutes to hours. It is usually impossible to keep playing after the injury due to pain and swelling.

After injury to your ACL the acute pain and swelling subside over time and in most people, it takes about 2-3 months to reach a level where they can think about playing sports again. Those who seem to get back to sports without surgery (about 30%) may have partial tears of the ligament and/or a lower activity profile. While the injured knee in this group may be looser than normal, the other structures of the knee, including ligaments and muscles, can make up for the ACL injury and allow a full return to activities in some people. Physiotherapy is crucial in training these muscles if surgery is to be avoided.

Even for those with a complete rupture, the feeling of stability does gradually improve over a 2-3 month period. If by that time, after appropriate rehabilitation, full confidence in the knee has not been restored, then ACL reconstruction should be considered if twisting, turning sports are an important part of life. If a return to those sports is made without a stable knee then a repeat injury is likely. Every time the knee gives way, or shifts unnaturally more damage can be done to the delicate cartilage and menisci.

In general patients with ACL injuries fall into one of three groups:

The first group contains people who do well and return to their sport without knee instability. This includes those patients who have partial tears or are able to compensate for the ACL injury with other structures such as muscles.

The second group contains people with a complete ACL tear who seem to do well until they play a sport that demands cutting or twisting activities. This group copes well in day to day life and thus, only requires surgery if a return to twisting type sports is desired.

The third group contains people whose knees feel frankly unstable in everyday life. This group may all benefit from surgery to give their knee a feeling of stability. That stability then protects against further injury and further damage to the knee.

Non-Surgical Treatments

Treatment ACL injuries cannot be standardized because of individual differences in injury patterns and expectations in regard to return to sports.

Non operative treatment is suitable for patients who have a stable knee for daily activities and do not desire to return to cutting and pivoting activities. For example, if running, cycling or swimming are the primary fitness activities an ACL reconstruction is likely not necessary. In fact, with appropriate rehabilitation there is a substantial group of people who are able to return to all their sports without an ACL reconstruction.

Physiotherapy can be very beneficial to allow an ACL deficient knee to stabilize sufficiently in order to avoid surgery in certain patients. Others may elect to try custom ACL bracing which in some individuals will allow adequate knee stability to return to their chosen sporting activities.

For those patients who are athletic and who do not wish to consider giving up sporting activities, it may be that a surgical procedure to reconstruct the ligament will provide the best chance of returning to a satisfactory level of performance.

Surgical Treatments

The decision to undergo ACL reconstruction depends on a number of factors including: activity profile (work, recreational activities), age and health of the patient and status of the other supporting structures of the knee. Those who sustain injuries to more than one ligament of the knee are more likely to have symptomatic instability of the knee and benefit from surgery.

Young patients with suspected meniscal tears, that may be repairable, benefit from ACL reconstruction in order to protect the meniscus from future injury. It is not possible to know whether a meniscal tear will be repairable until it is examined with the arthroscope (camera).