The increased risk of ACL injury in female athletes is due to multiple factors including differences in structure like the size of the knee. The size and shape of the knee joint is typically much smaller in women than in men due to the overall size difference of a woman versus a man. Smaller size leads to increased angles and different geometrical force patterns on the knee joint than the larger angles. We already discussed the Q angle and risks associated with larger Q angles. Even angles in the knee joint itself can cause an increase in force at the knee.
Here’s an example, picture the structure of a woman’s knee looking like the shape of the letter V and the structure of a man’s looking like the letter U. The ACL in the V knee has much less space and will much more likely get caught and tear versus the ACL in the U has ample room to glide as the femur and tibia translate into knee flexion and extension. Some of these differences in size relate to the tibial plateau. The tibial plateau is a spot in the knee where the tibia (lower leg) helps to form the actual knee joint. Think of it as the top portion of your lower leg bone that is underneath your knee cap forming the bottom part of the knee joint. It is one of the most important weight bearing areas in the human body. The increase in slope in the V knee causes an increase in anterior translation of the knee basically meaning that those people with an increased slope in the tibial plateau also have an increase in force on the front of the knee in rotation and twisting. One of the main mechanisms of the ACL is to prevent anterior translation at the knee and it is very common for an ACL to completely rupture due to excessive anterior translation. That being said, those with an increase in slope at the tibial plateau like most females and some males tend to have a much larger incidence for ACL injury because of the increase in force at the spot in the knee.
It is also very interesting that in most tibial plateau studies a large percentage of women have an increased slope at the tibial plateau and only a small number of men, but of the men who do have an increased slope many of them subsequently tore their ACL. It can be said that more convincing data has been reveled from the men studied with increased tibial plateau because most all women have that deviation which is one major reason for the 2-10x increase in ACL injury rates in women versus men. The men with the deviation also have a higher risk for ACL injury than men without the deviation. X ray can detect the tibial plateau slope angle and further studies will be conducted on risk factors for men and women with increased slope at the tibial plateau.
While we cannot change our anatomy, reducing the force on the knee joint can help aid in a decreased injury risk. Women’s knees automatically have more against them in the terms of injury risk but this is even more reason to assess and train our athletes based on their biomechanical restrictions and compensations. By detecting increased angles at the tibial plateau in men and women alike we can gain a better understand of the structural differences leading to ACL injury and incorporate corrective exercise training programs to athletes with increased risk of injury. By gaining strength in the proper muscles and preparing the lower body for change of directions, and deceleration moves in a safe environment; all athletes will be much more equipped to play sports safely and injury free!