We've all heard the news that Kiko Alonso injured his left ACL Sunday against Dallas. This is the same knee that he had reconstructed last July. The internet is saying he has a partial tear, while Les Bowen states that it's a grade 2 sprain. Alonso is to meet with Dr. James Andrews for a second opinion. What exactly is his injury? Is it a partial tear or a sprain? And what does this mean for this season?
A ligament strain is a partial tear. There is a spectrum of sprain/tear from very mild with no laxity, or looseness, to a complete tear. Partial ACL injuries come down to how stable, or loose, the knee is and whether the athlete can play without instability/giving way. Typically, a grade 2 injury stretches the ligament to the point where it becomes loose. This is usually referred to as a partial tear.
An MRI is helpful to see if the reconstructed ACL is injured but can't assess the degree of laxity/looseness. The stability of the knee is best assessed with a physical examination. Often times, a device called a KT 1000 is used to give an objective measurement of the looseness. Generally, if the involved knee has more than 3-4 mm difference compared to the uninjured side the knee will be unstable.
However, if the ACL laxity is within an acceptable range, rehab may allow the athlete to return without surgery. We call these athletes "copers" as they are able to function with a lax ACL. However, most athletes with a partial ACL injury are unable to return to cutting and pivoting sports without surgery. Another thing to consider is that this is Alonso's 3rd ACL injury which may mean he is predisposed to repeat injuries.
As we await the results for Alonso's second opinion with Dr. Andrews, let's hope he has a stable, partial tear with only minimal laxity. This would give him the best shot at returning this season.