Why ACL tears are more common in females

Why ACL tears are more common in females

When Title IX was passed in 1972 prohibiting sex discrimination in any educational program or activity including sports, it opened up a whole new world particularly for girls and women interested in athletics.  This piece of legislation also opened up to an almost epidemic rise in ACL injuries among female athletes where women are at least twice as likely to injure a knee ligament as a man. 

The ACL (anterior cruciate ligament) is one of four main ligaments within the knee that connect the femur to the tibia.  The knee is basically a hinged joint held together by the medial collateral (MCL), lateral collateral (LCL), anterior cruciate (ACL), and posterior cruciate (PCL) ligaments.

The ACL runs diagonally in the middle of the knee.  It provides stability for the knee by limiting the amount of forward translation of the tibia (lower leg bone) on the femur (upper leg bone) and provides rotational stability.

Why women are more prone to an ACL injury

Each year there are between 100,000 to 200,000 ACL ruptures in the United States.  Injury to the ACL is the most common knee joint injury among particularly among athletes.  It tends to occur in high demand sports involving planting and cutting, jumping with a poor landing, stopping suddenly, or changing directions quickly.  ACL injuries can also occur in noncontact sports such as soccer, basketball, or skiing.

Women are more prone to an ACL injury than men for several reasons:

·      Women have a proportionately wider pelvis where their thigh bones angle in more sharply from hip to knee causing greater stress and instability in the knee.

·      Ligaments in women tend to be more lax – particularly in the ACL.

·      Women tend to have smaller and weaker leg muscles than men.

·      Women tend to have an imbalance in the strength ratio between their quadriceps muscle (muscle in the front of the thigh) and their hamstring muscle (muscle on the backside of the thigh).

·      Female athletes are more likely to use their quadriceps muscle to slow down from a sprint which causes instability in the knee. Men tend to decelerate using their hamstring muscle to absorb the change in speed providing more protection to the ligaments of the knee.

·      There are biochemical differences between men and women in how they land on their feet when running or jumping.

·      A woman’s menstrual cycle may also make them more prone to knee injuries.  Both circulating hormones of estrogen and realxin give ligaments strength and flexibility.  When these hormones fluctuate during a menstrual cycle, it may influence the function of the nerves and muscles. 

·      A University of Texas study found that teenage girls on oral contraceptives had fewer ACL reconstructions than nonusers. 

·      Another study found that testosterone in men may contribute to the ACL’s ability to withstand loads possibly explaining why men have fewer ACL injuries.

How to protect the knee from an ACL injury

There are several things both men but certainly women can do to protect and prevent an ACL injury:

·      Strengthen and stretch your hip and leg muscles, particularly the quadriceps and hamstrings.

·      Do plyometric jumping exercises and balance training.

·      Perform simple exercises of partial (not full) squats, lunges (avoid going too deep), leg presses and curls, bridges, and squat jumps.

·      Avoid full leg extensions with heavy weights and locked knees.

·      Avoid running downhill, cycling with the seat too low or gear too high or taking large steps on the stairs or on a stair-climbing machine.

·      Anyone with an existing knee problem should work with a physical therapist or trainer for more specific exercises and to avoid further injury.