As I always mention in this column, I cannot give specific medical advice in any format, email, this blog, or on my show. And this column will be no different. I use the question, though, because athletes and athletic patients ask me a similar question very frequently. So it is a good opportunity to clarify the idea of a partial ACL tear.

Rohan asks:

Dear Sir,
I want to know information about my ACL injury. Eight months ago, I was playing football and got an injury in my right knee. The MRI report says it is an ACL injury. Specifically the MRI report says…
1. Partial-thickness interstitial tear in the anterior cruciate ligament
2. Grade 1 tear in the posterior horn of the medial meniscus
3. Traces of a joint effusion
When I ask my doctor, he told me that my ACL has been 50% damaged. How will it become normal – either it requires surgery or it will be good by medicine. 

There is a lot of misconception about ACL tears, and more specifically partial ACL tears. What is a partial tear? Does it need surgery? Will it heal on its own? Can I just brace my knee? Can I play sports with a partial ACL tear?

Part of the problem stems from the fact that the term is a radiology one. By that I mean that it is based on the fibers of the anterior cruciate ligament and what percentage of them are torn. Obviously in a complete tear, the ligament and all of its fibers are torn. But in a partial ACL tear, 30% of the ligament fibers might be ruptured, or 80% might be torn. It is based completely on the MRI images. And as such, a “partial” ACL tear diagnosis is only part of the story.

What is more important, at least to me, is whether or not the ligament is functional. The role of the ACL in general is to provide translational and rotational stability to the knee. An athlete can have 50% of the ligament intact and still have a stable knee, or she can have her knee give way with cutting or changing directions even though 50% of the fibers (as estimated by MRI) are intact. When the initial injury occurs, some of the fibers might become stretched out, despite remaining intact, so in essence they are not providing the necessary stability to the knee.

So to me, a “partial” ACL tear means nothing. It gets back to what I just said that what matters is whether or not the ACL is functional. And that is more of a clinical diagnosis. If the athlete is feeling that his knee is buckling with activity, then that “partial” ACL tear still needs reconstruction because it’s not doing what it needs to do. Yes, there are some signs that a ligament with some fibers still intact is essentially nonfunctional, such as a specific pattern of bone bruising that you see on MRI. But sports medicine physicians can also determine it by examining the knee and testing its rotational stability.

And to be honest, I don’t think a partial ACL tear, where some of the ligament fibers remain intact, is actually that common. In my experience, when patients come in to see me after an injury in soccer, football, basketball, cheerleading, or many other sports with the classic description of an ACL injury, and the MRI they bring has a radiology report that describes a “high-grade partial tear of the ACL,” examination of the knee almost always reveals that it’s unstable.
Soccer player suffers a partial ACL tear

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