Article from BMH
for 2 March, 2006
Brattleboro Reformer

Prevention Key in Costly Knee Injury to Anterior Cruciate Ligament
by William Vranos, MD

The anterior cruciate ligament (ACL) is the primary internal stabilizing ligament of the knee. Intact, the ACL prevents excessive rotation, translation, and angular deformity at the knee. Thus, when an athlete sustains an ACL injury, he/she usually cannot participate in cutting or jumping sports due to the resulting instability in the injured knee. Long term, the frequent episodes of instability “giving way” result in sheer injuries to the knee, cartilage tears, and early arthritis. Operative reconstruction allows approximately 90% of patients to return to athletic activity at or near their pre-injury level. However, re-injury is more common and injured patients, even with successful reconstructions, are less likely to remain in high demand sports later in life. Approximately 100,000 ACL injuries occur yearly. About 75% of these are reconstructed at a cost to the health care system of about one billion dollars annually. The cost of disability from this injury is unknown, but obviously significant. Thus, while recent arthroscopic cartilage repair and ligament reconstruction techniques have allowed patients to return to high levels of function, a current focus of a significant amount of research is on prevention of this potentially devastating injury.

The impetus for increased research comes from a dramatic increase in ACL injuries in the past 20 years, particularly in female athletes. Nationwide, approximately two of every three sports-related ACL tears occur on women. One in ten female basketball players (in Division I) will tear an ACL during their four-year college career. My own experience locally mirrors this. I reviewed the first 100 ACL reconstructions that I performed when I came to this area. Fifty-five were in women and forty-five in men. However, some of the men suffered a torn ACL in non-sporting events, mostly vehicle accidents like ATV’s or dirt bikes. All of the women had torn theirs in sports, and most injuries in both males and females were caused by a non-contact, deceleration mechanism such as planting to change directions or landing from grabbing a rebound.

An interesting study of female college soccer players showed significantly more ACL injuries occurring in the second half of the season. Researchers have noted that females have greater knee alignment (valgus), with greater rotation at their hips when they stop quickly. Women also tend to have greater joint laxity than men. There may be hormonal influences on ligament strength as well. Finally, women have weaker posterior (gluteal) and hamstring muscles in relation to their quadriceps muscles. The net result of all this is that women tend to decelerate on a straight leg that rotates inward, the classic position to tear an ACL. Preventive bracing has not been shown to help.

These observations have led to research on injury avoidance. Can athletes be trained to avoid this action which consistently leads to injury? Early studies suggest that it’s possible. Programs which combine (plyometric) jumping drills and stress proper jumping and landing techniques along with a strengthening and stretching program which focuses on the gluteal and hamstring muscles have preliminarily shown success in reducing the frequency of ACL injuries.

While larger, well controlled studies need to be performed, these “sportsmetric” programs inherently make sense. The key would seem to be intensity. Many local therapists and trainers offer coaches seminars or private programs for athletes, usually for a fee. In view of the fact that late season injuries seem more common, and since the goal is to retrain entire muscle groups to function differently in common situations, these training techniques must be incorporated into the regular practice and strength training routines of the female athlete. The younger the athlete starts training, the better. While the usefulness of these programs is not clearly defined, early results are encouraging, especially in female athletes, where ACL injury rates have clearly been shown to decrease with these programs. Unfortunately, most studies to date have had flawed designs.

Despite this, it would seem reasonable to conclude that these training techniques should be incorporated into the female athletes’ training regimen, hopefully at an early age. It is hoped that research currently underway will better define the type and intensity of training programs needed to definitively decrease the rate of ACL injuries.

Next month, Treatment of ACL Injuries