Why do Partial ACL injuries occur?

Injuries to the ACL or Anterior Cruciate Ligament are becoming more and more common. The ACL is composed of two pieces, or bundles — so it is possible to suffer only a partial ACL tear, as opposed to a complete ACL rupture.

What is the Anterior Cruciate Ligament

The anterior cruciate ligament — ACL –is one of the more vital and more easily injured ligaments within our knee. Ligaments are very tough, fibrous tissue structures which hold our bones together and allow us to bend, twist, pivot and rapidly accelerate and decelerate and yet maintain stability of our joints. The ligaments of our knee hold it together. Most ACL ligament injuries in the knee are non-contact in nature.

ACL Tear

If you have sustained an injury to your knee during a pivoting, or twisting incident, you felt a pop and then noted the inability to walk — as well as significant swelling within your knee — there is a significant chance that you have injured your anterior cruciate ligament. The anterior cruciate ligament or ACL is the most commonly injured of the four major ligaments that exist within our knee. Most patients who have sustained an injury to their ACL will have enough discomfort and enough of a disability that they will seek attention either in an emergency room or in orthopedists’ office fairly rapidly. Many of those patients will be indicated for an MRI to better ascertain whether or not an ACL tear exists. Even though the literature is fairly clear that a physical exam is as good if not better at predicting the integrity of the ACL, many surgeon still rely on the imaging studies to arrive at a final diagnosis.

Complete ACL Tears:

A complete ACL tear involves the complete disruption of all of the ligament tissue that connected both the femur and tibia. You may simply possess discomfort, pain and swelling – – – or you may perceive that the knee is unstable and feels like your knee wants to buckle or give way. We have covered the treatment of complete ACL tears elsewhere within this website, and whether or not ACL surgery is necessary as well. I recently placed two ACL Surgery blog posts on this site. The first will help you determine if ACL Surgery is necessary and what questions you should ask your surgeon. And a follow through post of steps you should take before surgery and after surgery to minimize the risks of complications and improve your overall results following an ACL reconstruction.

Partial ACL Tears:

A partial ACL tear involves an injury to only a portion of the ACL. Unfortunately, a partial ACL tear is more of a radiology or MRI diagnosis than an orthopedic diagnosis. What do I mean by that? We treat patients, we do not treat MRI findings.   Many patients who sustain a partial ACL tear will be able to return to their prior level of activity without complaints of buckling, instability or giving way. Unfortunately, a fair number of you will not be able to return to your prior level of activity because your knee feels unstable or loose.

What I’m getting at is simply the fact that we do not look at your ACL tear as being “partial” or “complete”, we look at your KNEE as being “functional” or “non-functional”.

If you have a functional partial tear of your ACL, that means that you have torn a certain portion of your ACL fibers, however, you are still able to participate in sports without the feeling of the knee giving way or being unstable. If you possess a nonfunctional partial tear of your ACL, that means that you have torn enough of your ACL fibers that your knee no longer feel stable. That means that you are at risk of further injury if you return to your prior level of sports participation. Every time your knee buckles or gives way you run the risk of tearing other structures within the knee, such as the medial or lateral meniscus. If you sustain tears of either the medial or lateral meniscus, which are the shock absorbers with within the knee, then you are at risk of developing osteoarthritis. You therefore want to eliminate or minimize the risk of buckling, instability or giving way and therefore a patient who presents with a partial ACL tear, who complains of instability, will likely present as an appropriate candidate to consider an ACL reconstruction or possibly an ACL augmentation.

Repair Options – If Partial ACL tear surgery is necessary:

The difference between an ACL reconstruction and an ACL augmentation is fairly simple. During the process of an ACL reconstruction we will reconstruct or replace the entire ruptured ligament. Anatomically, the ACL is composed of two separate bundles and a complete reconstruction will compensate for both of those bundles. In an ACL augmentation, you have only sustained a partial tear. That means that a portion of your ACL remains intact and should be normal. Many competent sports medicine orthopedic surgeons are capable of reconstructing only the torn portion of the ligament, leaving the normal portion alone. There are many advantages to an ACL partial tear augmentation over a full ACL reconstruction. While the discomfort, and the nature of the surgery is virtually identical – – – it is far more likely that someone who undergoes an augmentation will have a much more natural feeling knee when all is said and done. The reason for that is because the normal ACL has certain nerves within it. Those nerve fibers give the brain certain feedback as to the position of the knee joint. It turns out that those nerve fibers are quite important. If we preserve the intact portion of your ACL, then we are preserving those nerve fibers and hopefully preserving the integrity of your knee in the long run.