Anterior Cruciate Ligament Injuries

The anterior cruciate ligament is the most commonly disrupted ligament in the knee.

Our understanding of the anterior cruciate ligament and its' importance to knee stability has increased greatly over the past twenty years. Similarly, techniques for diagnosing the injury and surgical intervention have improved.

The normal anatomy of the human knee is depicted in Figure 1. The cruciate ligament and the collateral ligaments provide stability to the joint. The menisci function as a shock absorber and also serve to enhance joint lubrication. The articular cartilage lines the inside of the knee joint and allows for its' smooth movement.

When the anterior cruciate ligament is torn, it is commonly associated with injury to one or more of these other structures. Injuries to the anterior cruciate ligament occur most often in athletic activities, but may occur in work injuries, accidents and non-athletic activities. The injury can occur with or without contact. It may occur with a sudden change in direction, or a change in speed (deceleration injury). It may occur with the body falling over the fured leg, or with a hyperextension injury to the knee.

Often, when the injury occurs the individual will hear a "pop" or the sensation of a "tearing" inside the knee. This is usually followed with difficulty in weightbearing and progressively decreasing knee motion as swelling develops. If untreated, a significant number of knees will go on and be a problem and are unstable and referred to as a "trick knee." They tend to give out or buckle unexpectedly.

Approximately one third of the patients who injure this ligament and do not place high demands on the knee will experience relatively few problems and lead a fairly normal life. Another one third will have problems with the knee, but these problems will be related only to specific athletic activities. These people could live with their knee satisfactorily if they would give up lateral movement type sports. Approximately one third of those sustaining the injury will have problems with their knee in the activities of daily living. The knee will unexpectedly go out with simple activities.

Because all injuries to the anterior cruciate ligament do not have the same instability pattern, the treatment needs to be individualized. Much of the treatment is based on what the patients are willing to give up. At the time of the initial injury it is often difficult to predict who will experience a significant problem and who will not. For this reason every anterior cruciate ligament injury requires a discussion if what expectations the patient has, and what they are willing to give up. Patients who should consider surgery are those who are quite athletic and know that they would be unwilling to give up certain activities.

Patients with an old anterior cruciate ligament rupture need to avoid recurrent giving way and buckling. If these episodes are associated with pain and swelling, and are frequent the knee can develop progressive wear and tear activities. These patients should consider surgical reconstruction, or they should change the demands they are placing on their knees.

Reconstruction of the anterior cruciate deficient knee is a surgical procedure. There are many different ways to reconstruct the ligament but the preferred method at this time is to use a biologic tissue. Most frequently a tendon is taken from another part of the knee. This is called an autograft. "Auto" meaning self. An alternative is using tissues donated from other individuals. These are called allografts (from another).

The technique for rebuilding the anterior cruciate ligament has improved significantly and can be performed in an arthroscopically-assisted manner in most cases. Using the arthroscope allows for smaller incisions, shorter hospitalization and less postoperative pain, and is usually associated with more rapid rehabilitation.

Reconstruction of the anterior cruciate ligament may require being.in a brace for up to six weeks and being on crutches. The total rehabilitation time varies between six to twelve months following this type of surgery.

The anterior cruciate deficient knee will often have an associated meniscus tear. The MRI (Magnetic Resonance Imaging) is a special test that can accurately confirm meniscal tears without exposing the patient to radiation. The test is expensive and it is obtained only in these cases where additional information is needed.

Some people elect to have the meniscus surgery done and live with the anterior cruciate deficiency. This more limited surgery will often make the instability more predictable. It is a more limited procedure requiring just a few hours in the hospital and a much shorter rehabilitation. However for those desiring to resume high level activities this is usually not satisfactory. The meniscal surgery includes either partial removal of the damaged portion or suturing the tear. Which of these techniques is best is decided at surgery.

In summary, the anterior cruciate deficient knee is one of the more challenging problems facing the knee surgeon and sports medicine expert. The accurate diagnosis and treatment of any given knee injury requires a careful history and physical examination as well as x-rays, and in some cases an MRI (Magnetic Resonance Imaging). After the determination of the 1igament problems and associated meniscal involvement, treatment is dependent upon an individualized situation. This varies with the particular injury, the life style of the patient, and their future expectations.