An injury that has stuck with Chicago sports fans for some time now is the contralateral knee injury sustained by Derrick Rose when he was a member of the Bulls. A contralateral injury is the phenomenon of an injury to the “good knee,” or opposite knee, after surgery or during ACL surgery recovery.
For competitive athletes a torn ACL is a devastating and life-altering injury. The overall success rate for return to competitive sport after surgery is in the range of 75% to 90%. But this return to competitive sports is also one of the known risk factors for contralateral, or opposite knee injury and it is more common than you might think. Research shows a tear of the ACL in the previously un-injured knee after successful return to sport status post ACL reconstruction can range from 3%-11%.
Factors that have been shown to increase risk of opposite side ACL tear include age of 18 and younger, return to competitive sports, and male gender. The highest risk time period is within 1-4 years after the ACL surgery.
In recent years many surgeons have begun to extend the recovery time for ACL reconstruction from a range of 4-6 months to longer time frames averaging 9-12 months. This may be beneficial to allow more time for surgical healing and rehabilitation of the knee to re-gain strength, agility, and overall performance. But despite this a certain number of young athletes will face a new ACL tear in the previously normal opposite knee.
One key concept in the realm of ACL tears is proprioception. This is the body’s ability to know where a body part is in time and space, and to respond appropriately to protect the joint. There are several nerve fibers in the normal ACL that communicate this information to the central nervous system and Brain. We know that this feedback loop is disrupted when the ACL is torn and a large part of the struggle with postoperative rehabilitation is trying to re-establish these neural connections. Some research has shown that an ACL tear in one knee may also disrupt this feedback loop in the central nervous system for the opposite normal knee and leave it more vulnerable to a tear.
Another risk factor for contralateral ACL tear is fatigue in the good knee post surgery. It is very common to focus diligently on the surgical knee during recovery while allowing the good knee to become fatigued and weak while it is carrying the extra load. So longer recovery times may benefit the surgical knee, but could add to the fatigue of the good knee. It can often be imperceptible that by the time the surgical knee is ready, the good knee may be worn out, and it is at this very moment that many athletes are returning to sports. A strong focus on strength and function of the good knee when nearing the return to sport may help to decrease this risk.
Thankfully, in the case of Derrick Rose, he did not sustain another ACL tear but rather a torn meniscus. However, the issues mentioned above certainly may have played a role in the subsequent injury. He is a young, highly competitive athlete who underwent ACL surgery, had a prolonged recovery time, and likely had fatigue in the good knee.