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Anterior Cruciate Ligament (ACL) Injury

The following is designed to present an overview about an Anterior Cruciate Ligament (ACL) injury so that you might better understand what it is and what the treatment options are.

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This is a very serious injury to the knee, as ligaments are structures that give the joint stability. The anterior cruciate ligament (ACL) is one of the most important ligaments and when injured, it is one of the more difficult to treat. It is located in the middle of the knee joint and goes from the femur (thigh bone) to the tibia (shin bone).

When it tears, it almost always tears like a rope pulling apart. Before a tear in the ligament actually occurs, it is usually stretched beyond its ability to recover to its original length (which means it has lost its elasticity). This means that some of the ligament that appears intact, may actually be seriously injured and will not function as a normal ligament. Most tears of this ligament, however, are complete and the ligament is usually shredded in its mid-substance.

A good blood supply is necessary for healing soft tissue and bony injuries. Unfortunately, the anterior cruciate ligament has a poor blood supply and the chances of it healing after tearing are minimal. These factors among others also make it almost impossible to repair this ligament by just sewing the ends of the tear back together again. Years of investigation have proven conclusively that this will not work. What can be done for this injury will be discussed at length further on in this handout.

Once the ACL is torn, the knee remains unstable allowing the knee joint to move in directions that are not normal and not intended. This can happen suddenly, as when trying to jump or change directions quickly, causing the knee to “give way” or “pop out”. This abnormal motion can result in pain and possibly additional damage within the joint, such as a torn cartilage.

The cartilages or menisci between the tibia and femur serve many functions. The more important ones deal with load transmission, stability of the knee joint, and lubrication of the joint. One or both of these cartilages are torn in 50-70% of the patients with acute ACL tears. In patients with a torn ACL for more than a year,  the chances of a torn cartilage increase to 90-95%. Therefore, although the torn ACL is the major problem, there is a good chance for a torn cartilage as well.

In treating the meniscal cartilage tears, it is important to save as much as possible. Unlike the ACL, some types of cartilage tears can be repaired. A good blood supply is found in the outer third of the cartilage and certain tears located in this area are repairable. Suturing of these tears, either arthroscopically or through an open incision, is usually recommended. If the tear is felt to be un-repairable, the cartilage will need to be partially or entirely removed, depending on the severity of the tear. 

Knees with a chronically torn ACL are at a high risk of developing premature arthritis. This usually occurs secondary to the instability, the cartilage tears, and repeated injuries to the knee. This is the same kind of arthritis that occurs as we get older, only it can happen at a much younger age and more severely, especially if the injury occurred in the teen years.

Even with proper surgical treatment, arthritis can still develop. However, surgical reconstruction of the ligament generally will decrease the severity and retard the progression of the arthritis, especially in those cases where the cartilage are not torn or are saved by repair.

Instability of the knee is a significant disability that is experienced by virtually every patient whose ACL is injured and that is involved in activities that require sudden stops/starts, change of direction, jumping or twisting. Missteps, such as going down stairs, stepping off a curb, or walking on rough ground, can also cause this sensation of instability. Therefore, activities that require a sudden change in momentum and direction are generally the ones most significantly hampered by a torn ACL.

An athlete’s knee in particular would be seriously compromised by this injury. Normal daily activities can also be difficult secondary to the absence of the support of this ligament and frequently from the presence of a torn cartilage. Sensations, such as, the knee giving way or popping out of joint, occur combined with pain (sometimes severe), and usually swelling.

It is evident from the above information that this is a very difficult and disabling injury. The knee can be improved with surgery and hopefully eliminate the previous problems caused by the lack of an ACL and by tears of the cartilages. Even with current treatment options, the knee cannot be completely return to “normal.” However, surgical reconstruction is an attempt to make it as close to normal as possible.



Use crutches and participate in an appropriate rehabilitation program with gradual attempted return to desired actitivies. This would take a minimum of 4-6 weeks. A brace to compensate for the torn ligament would be used for activities. However, these have not proven to be satisfactory. A torn cartilage could also be present which would continue to cause dysfunction and disability with further damage to the knee. If the cartilage was initially repairable, it may not be after one or more re-injuries occur. Although treating the injury this way is an option, experience has shown that the vast majority of patients will continue to have difficulties with the knee as described above, unless they become rather inactive or sedentary, and avoid almost all athletic and work activities that put stress on the knee. This type of treatment is not our recommendation for “young” active individuals.


This option involves examining the knee under anesthesia, placing an arthroscope in the knee, and partially removing or repairing the cartilage as indicated. This option does not do anything for the torn ligament or to stabilize the knee, but does address the cartilage pathology. After surgery, the knee would be rehabilitated and placed in a brace during activities.

If you continued to experience problems with the knee slipping out and giving way, then a reconstructive procedure could be performed at a later date. The disadvantage of this treatment option is that if you continued to have episodes of instability, re-injury to the knee could occur, with further injuries to the cartilages and acceleration of the degenerative process. Interim disability, dysfunction acceleration, degenerative changes, and torn cartilages are the risks involved with postponing the reconstructive procedure.

In my opinion, the best treatment option would be to restore the injured knee to as close to normal as possible. As the ACL cannot be successfully sutured back together again, it would need to be reconstructed using other body tissues to stabilize the knee. If a cartilage repairs is attempted without stabilizing the knee, then 40-60% of these repairs will re-tear within the next 1-3 years. With satisfactory stabilization of the knee by reconstruction, the incidence of cartilage re-tears should be less than 10%.


The third and last treatment option would be to arthroscope the knee, to address the cartilage pathology by partial removal or by repair, and to reconstruct the ACL. Reconstruction of the ligament can be with an, AUTOGRAFT (your own tissue obtained from elsewhere in your body, usually the affected leg), or with an ALLOGRAFT (tissue from organ donors).  Artificial or synthetic ligaments are basically no longer used and were only available for use in knees that had previously failed reconstruction as per FDA guidelines.

Dr. Longobardi offers unique office services:

  • A Creative tracking system for patient examination
  • Quick, confidential access to one's medical history
  • Digital X-Rays at the time of examination

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