Defining Knee Injury, what is the ACL, and how do you damage it?

One of the more common knee injuries is a tear in the ACL, a tough band of tissue that joins the thigh bone to the shin bone. This damage can occur from a number of scenarios; however, they are more often than not sport injuries. 

At Mount Sinai, we have noted that the most frequent causes for a torn ACL is a sudden change of movement, landing badly from a jump or fall, or the result of a collision in a tackle – scenarios which usually arise in high demand sports like soccer, football or basketball.

Outside of competitive sports, we find that people develop ACL damage by changing direction rapidly, stopping suddenly, and slowing down while running. These are all movements that are exaggerated when playing sports, which is why you are less likely to tear the ACL when not participating in high-level sport.

Female athletes have a significantly higher incidence of ACL injury than male athletes, this is believed to be due to physical conditioning, strength, and neuromuscular control. It is also believed to be linked to differences in pelvis and lower extremity alignment, increased looseness in ligaments and the effects of oestrogen in the body.

What is the ACL?

The anterior cruciate ligament runs diagonally through the middle of the knee and prevents the tibia sliding out in front of the femur as well as providing rotational stability to the knee. You can imagine it as an X running through the knee.

You also have collateral ligaments, which are found on the sides of your knees. These control the sideways motion of your knee and brace it against unusual movements.

Damage to the anterior cruciate ligament (ACL) may require surgery to regain full function of the knee – but this will be dependent on several factors such as the severity of the tear.

How severe is the damage?

As usual, we class the sprains into 3 classes which increase in severity incrementally.

·        Grade 1 – The ligament is mildly damaged. It has been stretched, nudged, or pushed ever so slightly out of its comfort zone. You will still be able to keep the knee joint stable.

·        Grade 2 – The sprain will have stretched the ligament to the point in which it has become loose and will most likely mean there is a partial tear to the ligament.

·        Grade 3 – This type of sprain is commonly understood and referred to as a complete teat of the ligament. It will have split into two pieces and completely destabilized the knee joint.

It is worth noting that partial tears are usually rare – most ACL injuries are near complete tears.

If you have recently torn your ACL and would like to speak to one of our physicians, please contact our switchboard at (212) 241-6321 to discuss options.