Injuries to the ACL of the Knee
July 28, 2022
Hello, and welcome to Yuma Health and Happenings. I’m Dr. Ron Clark, Orthopedic Surgeon and founder of The Bone and Joint Center of Yuma. Today, I want to talk about injuries to the supporting ligaments around the knee and a relatively common injury to the center stabilizing ligament called the ACL.
This injury is most frequently seen in sports accidents but can also occur to non-athletes who happen to twist their knee suddenly or who are involved with falls. Frequently, the individual will feel a sensation of “popping” when the ligament is damaged, and the knee will become painful and swollen. After a couple of weeks, the swelling will go away and the pain will subside, but the knee will not have the same capacity for movement and will tend to buckle uncontrollably in certain positions or situations.
The Anatomy of the Knee and the ACL
The knee is composed of three bones and four connecting bands called ligaments. The ones along the sides of the knee are called collateral ligaments because collateral, in Latin, means “along the sides.”
In the center of the knee are two bands that form a cross as they pass in front and behind each other. The one in front is called the anterior cruciate ligament, which, translated into English, means the “front crossing ligament,” and the one behind is called the posterior cruciate ligament, meaning the “backcrossing ligament.” The anterior cruciate ligament is abbreviated ACL and is frequently reported as such in the newspapers regarding sports injuries.
What Does the ACL Do?
The role of the ACL is to help keep the upper and lower knee bones centered directly over each other. It acts like a hinge—when the ligaments of the knee are all working, the knee can bend, twist, and turn quickly. This is very important for athletic performance in sports, such as basketball, football, and soccer. When the ACL is torn, the knee will slip out of position and can cause a player to lose their balance and fall.
I cared for a football team where a player had injured his ACL and not reported the injury. It was finally discovered, as he would attempt to evade tacklers by suddenly changing direction, but his knee would give out, and he would fall without even being so much as touched by another player.
The Effects of an ACL Injury
Worse than just the inability to play certain sports, the presence of an ACL tear in a knee may subject other parts of the joint to injury. The knee has special soft supports, called meniscal cartilages, placed between the upper and lower bones. These can be injured when the ACL tears or may be injured years later because of the knee continually slipping out of position. These meniscal cartilages play an important role in protecting the joint surface of the knee joint. Someone who has an ACL tear may be at an increased risk to tear one or both of their meniscal cartilages because of the slipping that occurs in the knee after an ACL injury.
One of the main reasons that ACL surgery is recommended is to preserve the meniscus tissues from additional damage. It is thought that by replacing the ACL in the knee, the meniscus cartilages may be protected, which in turn will protect the joint surface from further damage and ultimately early joint arthritis.
ACL Injury Treatments
Treatments for ACL tears are basically surgical reconstruction, where a substitute tissue is placed into the knee to replace the torn ligament. Treatment can also be non-surgical, where exercises are prescribed to re-strengthen the joint, and twisting activities are avoided so further damage to the joint is minimized. ACL surgery has about a 90% success rate, but only 50% of individuals can return to the same or better level of athletic performance afterward.
For individuals under the age of 40, ACL surgery is generally recommended, but there are some individuals older than that who have benefited from ACL reconstruction. Those who are under the age of 14 typically will need to avoid sporting activities until they have matured before having surgery, allowing the knee bones to complete their growth and development.
ACL Reconstruction Surgery
Every year more than 100,000 people in the US undergo ACL reconstruction, but the same number of individuals have an ACL injury and decide not to have surgery. Most individuals will be treated with a technique that will transfer a portion of a different joint tissue into the center of the joint to become the new ACL. This type of tissue is called an autograft because it originates from the person having the surgery.
In certain situations, a surgeon may recommend that the new ACL be reconstructed out of tissue obtained from a tissue bank from a human donor. This is called an allograft. While it is certainly easier to use tissue from another person, the problem is that the long-term results show that allograft tissue does not perform as well as an individual’s own autograft tissue. I personally recommend that only individuals over the age of 30 consider allografts.
For those who don’t have surgery, there is about a 10% rate of healing with observation. Those whose ACLs do not heal can still have a painless knee as long as they avoid sports or occupations that create twisting forces on the knee. It is possible for someone to elect not to have surgery initially and then change their mind and decide to have surgery later. However, they risk experiencing permanent damage to their knee if they participate in activities or sports that involve twisting movements. The younger the individual is at the time of ACL injury, the more serious the problem can be because the potential for arthritis development will be higher.
Recovering from an ACL Injury
Injuries to the ACL used to be considered career-ending injuries, but many brave athletes have been able to complete the months of rehabilitation and emerge with the capacity to return to the sports they love. While professional athletes get lots of attention, most ACL tears happen on the fields of high school, college, and recreational level sports. Fortunately, there have been lots of improvements in the ability of surgeons to accurately reconstruct the damaged ACL.