Torn ACL vs. Torn Meniscus

Knee injuries in sports are incredibly common because the knees are weight-bearing joints.  Most sports require running and pivoting of the foot in order to change directions quickly.  This can unfortunately lead to various types of knee injuries.  I am always asked by patients and athletes the symptoms of knee injuries.  Two very common injuries that athletes are curious about are a torn ACL and a torn meniscus.  Both of these structures are very different and when injured, each have a unique presentation.

The ACL (Anterior Cruciate Ligament) is one of 4 important ligaments in the knee along with the PCL (Posterior Cruciate Ligament), MCL (Medial Collateral Ligament), and LCL (Lateral Collateral Ligament).  It is responsible for holding the knee in place while also providing flexibility.  The meniscus is cartilage that functions to cushion the inside of the knee.  Here is a picture for some clarity (Photo credit fpnotebook.com):

The classic presentation of an ACL tear is a buckling and hyperextension (bending back) of the knee with a pop.  The pop in the knee can either be heard or felt by the athlete.  Since the ACL has a very rich blood supply, it will bleed quickly and will lead to immediate swelling of the knee.  The athlete is generally not able to keep playing that day once the ACL tears.

The meniscus, on the other hand, tears due to a twisting type injury where the two bones rub against the meniscus and cause a tearing.  There is usually no pop in the knee.  The meniscus has a poor blood supply and so it will bleed much more slowly and athletes will usually report swelling later that evening, 4 to 5 hours later.  Many times an athlete is able to keep playing through the injury and it is only diagnosed a few days later.  

Over the next few days, the symptoms are also very different.  Those with an ACL may report that the knee feels unstable or feels like it will give out.  The swelling may resolve and they may actually even be able to play again since the knee feels better.  This may, of course, lead to further injury since the athlete is unaware of the underlying injury.  An individual with a meniscus tear will have symptoms of pain, locking, or catching of the knee. They may also feel pain with activity as the torn meniscus continues to grind in the knee joint.   

These are the basic signs and symptoms of an ACL tear vs. meniscus tear.  These injuries can also get very complicated based on location of tear, degree of tear, and multiple injuries at the same time.  As always, have your doctor evaluate your injury to avoid further damage!