Front Inside Knee Pain Caused by a Loose Ligament

POSTED ON IN Knee BY Christopher Centeno

This past week, while seeing patients in Grand Cayman, I saw a woman who had gotten some relief from a first stem cell treatment for front inside knee pain, but she wanted more. What was interesting was that her remaining pain in this area of the knee seemed to be caused by a loose ACL ligament. How could a ligament in the middle of the knee have anything to do with why the inside of the front of her knee hurt?

What Is the ACL Ligament?

The anterior cruciate ligament (ACL) lives in the center of the knee and prevents the tibia (the larger lower-leg bone) from shifting forward. The ACL also stabilizes the tibia during rotational movements, and when the ACL becomes loose, it can cause rotational instability in the tibia, also causing pain. Most physicians who examine the ACL are looking for catastrophic instability that would require surgery. Hence, what often gets missed are loose ligaments that over time can lead to problems. In this patient, her traditional drawer test was normal, but a second, less-well-known ACL test showed issues. So how could this second positive test relate to front inside knee pain even though most physicians would have said her ACL test was normal?

The Drawer Test Shouldn't Be the Only Test in Front Inside Knee Pain

When a patient has an unstable knee, providers typically will only do what's called a drawer test, which looks at the anterior stability of the tibia, and doesn't test the rotational stability. It's possible that a patient could have rotational instability without anterior instability, so a normal result on a drawer test shouldn't lead the provider to conclude that the knee is fully stable. This was what happened with a patient of mine, whose case I highlighted in the video below. She'd had a normal drawer test, so when I pulled the tibia forward, it seemed to be fine; however, when I took it a step further and rotated the tibia, it was unstable compared to her normal side. She had initially injured the ligament in a ski injury, and the rotational instability from this old injury ended up causing some serious issues for her.

Loose ACL with Rotational Instability Leads to Knee Meniscus Overload

The medical terminology for her problem may seem almost medically Shakespearean: “ACL laxity leading to tibial rotational instability and anterior medial compartment overload.” This basically means the loose ACL caused a rotational instability of the tibia, which led to knee meniscus pain and possibly damage. Have you ever seen dominoes fall? It's the impact of the first domino on the second domino that causes the third and all subsequent dominoes to fall. When the body is injured, damaged, or sick in some way, there can be a domino effect as well, and this is the case with a loose ACL—it's the first domino. Even an ACL that is slightly loose—not something a surgeon would want to replace by any means—can have dramatic, long-term impacts on the anterior medial meniscus (or the front inside meniscus). You'll see in the video below that I used an ultrasound probe on the inside front of the knee to image my patient's meniscus, and then I rotated her good side and I rotated her bad side (the painful side). I saw huge differences just visually, but I was also able to capture those on the ultrasound, and you can see the ultrasound of both sides in comparison on the video. On the left, when I rotated the tibia, there was a little bit of motion of the tibia on the femur against that side of the meniscus, but it was not dramatic. On the right, when I rotated the tibia, there was a dramatic amount of motion seen on the ultrasound. In fact, I was going faster on the right because it was so loose. In the video you can see how that excessive motion is beating up her meniscus on that side every single time she tries to take a step, as the tibia rotates when you walk. And every single time she makes a pivoting movement, it beats up her meniscus and this corner of the knee even more.

Treating a Loose ACL with Orthobiologics

Loose ACLs can usually be stabilized using a precise injection of orthobiologics, such as platelet rich plasma or bone marrow stem cells. In the case of my patient highlighted in the video, I will harvest and inject the patient's own bone marrow stem cells, as I have done for many, many years in the treatment of ACLs and to help patients avoid unnecessary ACL surgery. The upshot? Where the knee pain is located and what's causing it are often two different things. There's often a disconnect between what the problem is and where it hurts. If your drawer test comes back normal, but you are clearly still experiencing front inside knee pain, a prescription for pain medication isn't the answer! Something isn't right, and it's important to find the root cause, not only to eliminate your pain but also to repair the issue before more dominoes fall and more damage is done!  

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