ACL deficiency and the effect on the Knee

Title of Article: ACL deficiency influences medio-lateral tibial alignment and knee varus-valgus during in vivo activities

Journal: Knee Surgery, Sports Traumatology, Arthroscopy

Relevant Findings:

1. 1. Patients were asked to perform a single step forward and a single leg squat. The goal was to compare an injured knee with the contralateral one.

   2. Statistically significant differences (p < 0.05) were found for single leg squat along the frontal plane: ACL-deficient knees showed a more varus angle, especially at the highest knee flexion angles (40°–50° on average), compared to the contralateral knees.

   3. ACL-deficient knees showed tibial medialization along the entire task, while contralateral knees were always laterally aligned. This difference became statistically relevant (p < 0.05) for knee flexion angles included between 0° and about 30°

What does it mean:

Joints can take quite a beating over the years and regardless of age joint pain is a very common problem, especially in the knees. This article brings to light a common problem found in people with ACL injuries. Take a look at figure 1.

Figure 1 shows the basic anatomy of the knee joint. The Anterior Cruciate Ligament (ACL) is the primary restraint to forward motion of the shin bone (tibia). The anatomy of the knee joint is critical to understanding this relationship. Essentially, the femur (thigh bone) sits on top of the tibia (shin bone), and the knee joint allows movement at the junction of these bones. Without ligaments to stabilise the knee, the joint would be unstable and prone to dislocation. The ACL prevents the tibia from sliding too far forward. The ACL also contributes stability to other movements at the joint including the angulation and rotation at the knee joint. The ACL performs these functions by attaching to the femur on one end, and to the tibia on the other.

Now imagine if the ACL is weakened or deficient. There would be improper stabilization of the knee joint. This study showed that ACL-deficient knees have abnormal tibial medialization and increased varus angle during single leg squat when compared to the contralateral good knees. This was most significant during flexion between 40°–50° on average (See figure 2). These biomechanical anomalies could cause a different force distribution on tibial plateau, explaining the higher risk of early osteoarthritis.

Additionally, this article brings light to various methods of rehabilitation trials that compare “open-kinetic chain” exercises (e.g., leg curl) versus “closed-kinetic chain” exercises (e.g., squat). In most of these studies, ACL deficiency patients showed less stress and pain on the ACL along with increased functionality. Additionally, it would be important to note the depth at which a person performs the activity. Take for example the squat, the majority of the stress that leads to pain and early osteoarthritis occurs between 40-50 degrees in patients with ACL deficiency. This could mean squatting to a point where the knee and hip are at 90 degrees to the floor or just below it would have less stress and strain on the knee joint and the force distribution. Improving health through fitness is important for preserving healthy and injured joints. So next time, squat to at least 90 degrees.