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Anterior Cruciate Ligament (ACL) Injuries – Then and Now

Russell F. Warren, MD looks back at how the understanding, prevention, and treatment of ACL injuries has changed over the last three decades.

Russell F. Warren, MD, orthopedic surgeon at HSS and former New York Giants team physician for over 30 years, has seen a vast spectrum of musculoskeletal ailments affect every kind of patient.

One of the most profound changes he’s seen in more than three decades of treating both professional and everyday athletes is in the understanding, prevention, and treatment of anterior cruciate ligament (ACL) injuries, some of the most frequent injuries occurring in nearly every sport.

Where is My ACL? Introduction to Knee Anatomy

The ACL is part of a complicated network of tendons and ligaments that help stabilize and support the knee. Specifically, the ACL prevents the shin bone (tibia) from moving too far forward on the thigh bone (femur) and keeps the knee from twisting inward excessively.

People of all ages, physical abilities, and conditioning can tear this ligament; however, it is particularly common in sports such as football, soccer, and basketball. Tears usually occur when an athlete stops suddenly and changes direction, as when running, pivoting, or landing after a jump. An ACL tear often occurs in conjunction with other injuries to the knee, including damage to the meniscus (the cartilage between the moving surfaces of the knee).

As one of the top orthopedic surgeons in the country and a pioneer in the field of sports medicine, Dr. Warren has witnessed a substantial evolution in the treatment of ACL injuries during his 30+ year career.

“In the 1960’s and 1970’s, ACL injuries were often missed diagnostically, treated relatively poorly, or not treated at all,” says Dr. Warren. “Physicians didn’t know enough about the ligament. In fact, there was an ongoing debate in the field as to whether the ACL played a significant role in the knee and whether to fix it at all.”

HSS Physician John Marshall, MD: The Pioneer of ACL Repair

Much of what is known today about the function and importance of the ACL, and early attempts to repair this ligament, can be attributed to the late Hospital for Special Surgery physician, John Marshall, MD.

A veterinarian before becoming an orthopedic surgeon, Dr. Marshall first developed an interest in the ACL after having studied and treated dogs disabled by this injury. Through his research, he discovered that ACL tears in dogs led to a breakdown of the knee that often included damage to the meniscus, and ultimately led to arthritis in the animal. After going to medical school and joining the staff at Hospital for Special Surgery in 1971, Dr. Marshall expanded his previous ligament studies, finding that when the ACL is injured, the meniscus absorbs greater impact and can tear, leading to a higher risk of arthritis.

“In the 1960’s and 1970’s, when an athlete sustained an ACL injury, typically, they kept playing,” says Dr. Warren, who worked alongside Dr. Marshall in the late 1970’s. “Then they’d tear their meniscus, tear the other meniscus, and years later come to us with severe arthritis. By that time, there wasn’t much we could do for them.” Dr. Marshall’s groundbreaking research in this area helped to confirm the importance of the ACL and the need for reconstruction.

Subsequent research on meniscal tears after an ACL injury led to the accepted practice of meniscal repair, rather than removal.

Physicians now understand that the meniscus functions as a shock absorber, distributing load across the knee. “In a knee where the meniscus was removed, even if the ACL injury was fixed, the athlete often still got arthritis,” explains Dr. Warren. “However, if you fix the meniscus and the ACL, the athlete’s chance of getting arthritis is lower and their chance of getting back on the field is much higher.”

The Modern Method: ACL Reconstruction Surgery

While an ACL injury once may have ended the career of an athlete, today doctors are able to successfully manage and treat the injury in a way that allows most players to return to sports.

“Whereas in the 1970’s HSS performed about five ACL procedures a year, today that number is closer to 1,000 a year,” explains Dr. Warren.

Early methods of surgery involved repairing the ligament or using a synthetic material to replace the ligament, but the failure rate was very high. Today, the most common corrective procedure for this injury is ACL reconstruction, which involves replacing the entire ligament with a tendon graft. In athletes who play sports that demand constant pivoting, ACL reconstruction surgery is often the best option.

Knee Arthroscopy: Minimally Invasive Surgery

In the 1980’s, surgical treatment of the knee was revolutionized by a minimally invasive surgical technique called “arthroscopy.” Done through a small incision in the knee using a combination of fiber optics and small instruments, arthroscopy allowed physicians to see the knee in greater detail and perform the procedure less invasively.

“We did our first ACL reconstruction arthroscopically at HSS in 1985, whereas other physicians around the country were performing open, large-incision surgery,” says Dr. Warren. “Arthroscopy changed the field because it made patient recovery much easier and enabled us to move towards more aggressive rehabilitation programs.”

Dr. Warren marvels at the improvement he’s seen in ACL rehabilitation over the last three decades.

“In the 1970’s, an athlete who had undergone ACL surgery was required to wear a cast and not move their leg for six weeks. As a result, the ligament often remained loose and did not stabilize the knee. In addition, when the cast was removed, the knee joint was very weak and stiff,” explains Dr. Warren. “Today, however, we know that a knee that lacks motion has a greater propensity to get arthritis, so achieving motion right away is important to try to prevent that. People who undergo this procedure can move their knee immediately after surgery and return home the same day. Two days later, physical therapy begins. In about six months, the majority of people can actively participate in sports again, including contact sports like football.”

Reducing the Risks of ACL Injury

Anterior cruciate ligament education and prevention programs today are also helping to keep more athletes on the field, especially female athletes who have a significantly higher risk of getting an ACL injury.

“Because research has shown that females on high school sports teams, especially in soccer and basketball, are approximately five times more likely to get an ACL injury than their male counterparts, there is a need to reach these kids early to help minimize their risk,” explains Dr. Warren.

Though a number of theories have been proposed as to why females suffer from ACL injuries at a much higher rate, including differences in anatomical structure, genetics, hormones, muscle development, or physical fitness, none have yet to be confirmed. “ACL tears are rampant in female athletes on high school sports teams,“ says Dr. Warren. “At HSS we’ve seen five or six female players on the same soccer team, for example, with ACL injuries.”

Dr. Warren and other sports medicine physicians at HSS are working to keep more young athletes on the field. “Learning proper techniques for jumping and landing, especially for female athletes, is an essential part of our prevention program,” says Dr. Warren. “Athletes can really reduce their ACL risk with specific training.”

Outcomes of ACL Treatment and Prevention

Today, improved education, training, and the management of knee ligament injuries at the high school and college levels have had a profound impact on the National Football League as well.

Dr. Warren, who has been examining the injury risk of potential players for the New York Giants at the NFL Combine for three decades, recalls the tremendous change he’s seen. “Thirty years ago, we had to reject approximately 80-90% of the players who had an ACL injury either because it had been missed or reconstructed poorly. Today when we look at the numbers, we pass approximately 90% of players.”

For the tens of thousands of people in the United States this year who may tear their ACL, the prognosis is positive. Once a debilitating, possibly career-ending injury for an athlete, an ACL injury today is a manageable condition that does not have to mean the end of a healthy, active lifestyle.

Every day, physicians and researchers at institutions like Hospital for Special Surgery are identifying even more effective treatments and developing new therapies for people with ACL injuries.


Russell F. Warren, MD
Attending Orthopedic Surgeon, Hospital for Special Surgery
Professor of Orthopedic Surgery, Weill Cornell Medical College

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Prepared by Teresa Lamb

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