The anterior cruciate ligament (ACL) is one of the most common, yet heartbreaking injuries of the knee. The ACL controls the rotational stability of the knee. This injury is most often caused when the knee comes in contact with the ground and is still twisting. This means it is possible when basketball players or soccer players pivot while running or a gymnast is twisting in the air and doesn’t quite make it completely around. It is also common to injure the ACL different ways such as overuse or structural alignment of the knee. The ACL, in simple wording, is a ligament that connects the femur to the tibia. In a little more detail, the ACL extends from the lateral femoral condyle to the crest of the anterior medial aspect of the tibia (Nessler, 2017). The ACL is composed of three twisted bands including the anteromedial, intermediate, and posterolateral bands (Prentice, 571). The ACL works with other muscles of the leg including the thigh muscles, and the hamstring group to stabilize the knee (Prentice, 571). The discussion on the ACL injury will include; prevention, diagnosis procedures, immediate care procedures, and rehabilitation.
There have been numerous studies done on ACL injuries, and many conclusions have come from those studies. The following are some facts that will go along with ACL injuries before getting into more detail. Most of ACL injuries happen in the beginning phases in late adolescents, while younger kids usually go through growth plate injuries (Cimino, 2010). ACL injuries are more prevalent in females than in males (Cimino, 2010). ACL injuries are very common and another factor to remember is the intensity of play. Usually playing a game, the risk is three to five times greater in tearing the ACL than that compared to practice (Cimino, 2010). When an athlete tears the ACL, they describe hearing a popping sound which is then followed by pain and swelling. Most of the time when the ACL is torn, it is a non-contact injury.
With the rate of ACL injuries at such a high percentage, there has been numerous studies on how prevent a torn ACL. When trying to prevent any type of injury, it is important that the athletes be in shape to be playing the sport they are pursuing. When preventing the ACL injury, there are two different factors to look at: the intrinsic and extrinsic factors. The extrinsic factors are something athletes have no control over while the intrinsic factors the athletes have full control over. Almost all the time there are more intrinsic factors than there are extrinsic factors, but that could also be based off the sport you are playing. There is so much an athlete can control to prevent an injury of any type.
Depending on which sport the athlete is playing, these can be adjusted. Some extrinsic factors include but are not limited to: safety of training facility, ground/playing field (wet or muddy conditions), level of competition, playing style, shoe surface, and weather (Cimino, 2010). These are all conditions that the athlete has no control over. If the sport is an outdoor sport, the weather is really something that can cause many injuries. If you are running outside on the field and slip because the field is wet and hurt your knee that would be an injury that is out of the athlete’s control. If you are playing a higher ranked team who is overall at a higher level and a more aggressive team it can be easier to have a possible injury, which would also be out of the athlete’s control. Although, these are some of the extrinsic factors, there are more, and they differ for each sport.
The intrinsic factors are pretty set and stone because these are factors that the athletes are in full control of. Some of these factors include: body size and limb girth, flexibility, strength, reaction time, foot morphology, hamstring strength, pelvic width, leg dominance, ligament dominance, quadriceps dominance, and small ACL size (Cimino, 2010). These are factors that the athletes are in control of, and they can work to improve. If an athlete is out of shape and not strong enough it can cause any type of injury, and this is something the athlete can work on. If the athlete is not flexible, it can cause injury. The athlete is in full control of flexibility and should spend time on this every day for 10-15 minutes after a practice if needed. The dominance of muscles is a bit harder to determine, but they can be determined by a DEXA (dual-energy X-ray absorptiometry) scan which gives so much information. If the on hamstring is way stronger than the quadricep on one leg, that is something to make sure the athlete is working. Overall, strength is a huge component to injuries. Athletes push themselves very hard every day and their bodies need to be strong enough to keep up otherwise and injury will occur.
Another factor to include in programs to prevent ACL injuries include a structured warm-up (Cimino, 2010). The warm-up should include techniques to improve cutting and jumping movements, balance board exercises to focus on knee position during unstable movement, plyometrics, and strength exercises (Cimino, 2010). Plyometrics help increase knee flexion at landing (Willadsen, 95). The balance board or any type of balancing training is beneficial in decreasing knee valgus angles and increase knee flexion at landing (Willadsen, 95).
Another way to prevent an ACL injury before it happens is shoe type. The shorter cleats are better for players on a synthetic or artificial field because the foot doesn’t become fixed to the surface but still allows controlled running and cutting (Prentice, 592). A prophylactic brace also helps prevent a knee injury, this method is more controversial than the shoe. These braces are worn on the lateral surface of the knee to protect the medial collateral ligament (Prentice, 592). The prophylactic braces are custom made for different athletes and are designed to control rotational stress or tibial translation (Prentice, 592). Both of these ways are simple ways to prevent ACL injuries. The shoe is more appealing to try because it is a change of shoe, wearing a bigger brace is a harder to do if there is not an injury already present.
There have been studies done to show what works when trying to prevent ACL injuries. The first study includes 43 females at the age of 13-18 years old. There were four different groups which included: plyometric training, neuromuscular training, core stability and balance training, or control group. The first group was assigned 60 minutes of standard neuromuscular training which included three specific 20-minute components of core strength and balance, plyometric, resistance, and speed training. The second group was 20-minute plyometric training. The third group was 20-minute core stability/balance protocol. The fourth group was the control group and performed their regular daily activities. The findings from this study included: plyometrics showed a decreased in hip adduction and plyometric/neuromuscular training bother resulted in increased knee flexion (Willadsen, 96). This study showed that plyometric training may be beneficial in reducing ACL injuries by helping increase knee-flexion angles and decrease hip adduction/knee valgus angles at landing (Willadsen, 96). Neuromuscular control should also be considered in reducing ACL injuries by decreasing hip adduction/knee valgus angles at landing (Willadsen, 96). The core stability group showed no effect on the knee and should not be used to decrease an ACL injury (Willadsen, 96).
Another study had 18 female athletes around the age of 14. These athletes were assigned to either a plyometric group or balance training group. The main findings from this study indicate after seven weeks of training, both plyometric and balance training decreased lower-extremity valgus (Willadsen, 96). Plyometric and balance training are beneficial to decrease ACL damage as both were found to decrease lower-extremity valgus and increase knee-flexion angles (Willadsen, 96).
The last study had 23 high school female athletes placed in three different groups. The groups include: plyometric, core stability, and a control group. After four weeks of training, plyometric training and core stability training both resulted in a decreased in knee valgus angle at landing (Willadsen, 96). During this study, the plyometric and core stability training also led to a decrease in knee joint flexion angle at landing, which is likely to increase the risk of ACL injury (Willadsen, 96).
Overall, the best way to prevent ACL injuries is to make sure all the intrinsic factors are the best they can be and continually work on those to improve them to become better. Also, incorporate plyometrics into a warm-up three to four times a week. It doesn’t have to be a lot, but doing a little everyday can improve the overall results when trying to prevent ACL injuries. Doing a structured warm-up is important to make sure the athletes are all on the same page and doing it to the best of their ability. Doing plyometrics are going to help only if they are done right, if the warm-up is not structured and the athletes are doing it by themselves with no one watching and correcting them if they need it, the plyometrics may not help in preventing ACL injuries.
There are many different tests to check to see if an athlete has torn his or her ACL. The most common test is the Lachman test, the anterior drawer test, the pivot-shift test, the jerk-test, followed by the flexion-rotation drawer test. (Prentice, 586). The final determination as to whether the ACL is torn or not is magnetic resonance imaging (MRI), this will show tears of the ligaments. Cimino et al. (2010) examined when tearing the ACL, there is also a 60-75% chance there is a meniscal tear, a 46% chance to have a collateral ligament injury, and a 5-24% chance that the collateral ligament is torn.
The Lachman test is the most common, yet accurate test used with ACL injuries. This test is best used right after an injury to the knee because it does not force the knee into a full 90-degree position, which would be very painful, it tests the knee at a comfortable 20-30 degrees (Prentice, 585). During this test, the athletic trainer has one hand stabilizing the leg while grabbing the distal end of the thigh (right above the knee cap) and the other hand at the proximal aspect of the tibia (right below the knee cap) and attempts to move it anteriorly (Prentice, 585). This is most likely the test the athletic trainer will use to test the ACL after injury before getting and MRI.
The anterior drawer test is when the injured knee is flexed at 90-degrees. The athlete will lay on the treatment table and flex the knee to 90-degrees with the foot planted on the table (Prentice, 584). This test the athletic trainer places the index finger on the hamstring tendon and if the tibia slides forward from under the femur, the test is positive (Prentice, 585). There is another test that is very similar to the anterior drawer test that is called the Slocum test. The Slocum test is when the foot planted on the treatment table is either internally of externally rotated (Prentice, 585). Both of these tests can be used to determine if damage to the ACL has been done, but this type of test is more painful than the Lachman’s test.
The pivot-shift test is a way to determine rotary instability and is very sensitive when the ACL has been torn (Prentice, 586). During this examination, the athletic trainer uses one hand to press on the head of the fibula, and the other to grab the patient’s ankle (Prentice, 586). To start this test, the lower leg is internally rotated, and the knee is fully extended; the thigh is flexed around 30-degrees at the hip while the knee is flexed (Prentice, 586). If the ACL is damaged there will be a palpable shift or clunk in the knee (Prentice, 586). The jerk-test is very similar to the pivot-test. During the jerk-test, the knee is moved from a position of flexion into extension (Prentice, 586).
During the flexion-rotation drawer test, the lower leg is cradled, and the knee is flexed between 15-30 degrees, with the tibia anteriorly rotated and the femur externally rotated (Prentice, 586). With the knee at 30-degrees of flexion, the tibia will reduce posteriorly, and the femur will end up rotating internally (Prentice, 586). There is another test called, Losee’s test, which is the same test except the patient is not lying supine but rather on the side (Prentice, 586).
All of these tests described above are different ways to test the damage of an ACL. Although all of these tests can be used, not all have the same outcome when it comes to accuracy of the injury. Every ACL injury will be different, and some may be hard to examine because of the pain and swelling and others may not have much swelling at all, it will be up to the athletic trainer to know what to do. Examiners must know that the Lachman test has been shown to be a consistently reliable examination (Cimino, 2010). The Lachman’s test has an 84% of accuracy, the anterior drawer test is at 62%, while the pivot-shift test is at 62% (Cimino, 2010).
When a patient first gets injured it is important for the athletic trainer to test to see if they think there is a possible ACL injury. If the athletic trainer thinks there is ACL damage, the athlete will then have to get an MRI to confirm the ACL tear. If it is confirmed the ACL is torn the athlete is required to reduce the inflammation and swelling in the knee prior to surgery (Biggs, 2009). Athletes are told to apply ice, compression, and elevation three to four times per day, which will help the inflammation and swelling slowly be eliminated (Biggs, 2009). Working on this before your surgery will be important, but it is also important the athlete does not participate in competitive sports.
Before the athlete receives surgery, it is very important to try to get them to complete passive range of motion (ROM) (Biggs, 2009). The inflammation, swelling, and ROM of the knee are improved, then the neuromuscular training is initiated before the surgery happens (Biggs, 2009). Before the surgery each patient is tested for quadriceps and hamstring muscle strength isokinetically at 60 and 180-degrees (Biggs, 2009). The strength measures attained on the uninjured knee are used as a post-operative goal for both knees (Biggs, 2009).
Just like any injury, rehabilitation is a very important step in returning to play. The rehabilitation process for an ACL injury takes about nine months, any sooner returning to play could cause a possible re-injury, and some athletes take a little longer to heal and will take longer than the nine months (Zadro, 2018). The goal of the rehabilitation stage is to restore pre-injury knee function and make sure the knee is properly strengthened and functional (Zadro, 2018). There are certain tests that the athletic trainer may want the athlete to pass before returning to play or performance of some agility and jump-landing drills, to resistance training and graded activity, which enhance improvements in strength and hop test performance (Zadro, 2018).
With the measurements taken before the surgery on the uninjured leg that is the goal the athletic trainer is trying to get on the reconstructed leg. The first week after surgery the patient should be on bed rest to eliminate any swelling (Biggs, 2009). While in the hospital on bed rest, it is important the athlete starts to work ROM at least three to four times daily (Biggs, (2009). Some of the exercises to work on hyperextension include: heel prop exercises, heel slides, wall slides, towel stretch exercises, and active hyperextension (Biggs, 2009).
Overall the rehabilitation stage is to get the athlete feeling strong in the recovering area and making sure there is no pain before being to play again.
In conclusion, ACL injuries are devastating and there is a long road to recovering when injuring the ACL. It is important to educate athletes on the intrinsic factors and how they can best prevent an ACL injury. The injury it such a detriment for some individuals and athletes can work on preventing the injury every day. As well as the athletes working on preventing the ACL injury, the athletic trainer as well as the coaches should implement the exercises into the warm-ups or conditioning of the athletes every day. If the athlete does have an ACL injury, it is important to follow the reconstruction phase and listen to the athletic trainer when working on getting range of motion back, even though sometimes it may be painful, push through the pain so the outcome will be what you except it to be. No injury is fun to deal with, but make sure the recovery phase is easy by doing what is asked.
- Biggs, A., Jenkins, W., Urch, S., & Shelbourne, D. (2009, February). Rehabilitation for Patients Following ACL Reconstruction: A Knee Symmetry Model. North American Journal of Sports Physical Therapy. 4(1). Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2953314/
- Cimino, F., Volk, V., & Setter, D. (2010, October). Anterior Cruciate Ligament Injury: Diagnosis, Management, and Prevention. American Family Physicians. 82(8). Retrieved from: https://www.aafp.org/afp/2010/1015/p917.pdf
- Nessler, T., Denney, L., & Sampley, J. (2017, September). ACL Injury Prevention: What Does Research Tell Us? Curr Rev Musculoskeletal Med, 10(3): 281-288. Doi: 10.1007/s12178-017-9416-5. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577417/
- Prentice, W. (2014). Principles of Athletic Training: A Competency-Based Approach. The McGraw Hill Companies.
- Willadsen, E., Zahn, A., & Durall, C. (2019). What is the Most Effective Training Approach for Preventing Noncontact ACL Injuries in High School-Aged Females Athletes? Journal of Sport Rehabilitation. Retrieved from: https://journals.humankinetics.com/doi/pdf/10.1123/jsr.2017-0055
- Zadro, J., & Pappas, E. (2018, October). Time for a Different Approach to Anterior Cruciate Ligament Injuries: Educate and Create Realistic Expectations. Sports Medicine. Retrieved from: https://www.researchgate.net/profile/Joshua_Zadro/publication/328078972_Time_for_a_Different_Approach_to_Anterior_Cruciate_Ligament_Injuries_Educate_and_Create_Realistic_Expectations/links/5bea1985299bf1124fce1f2f/Time-for-a-Different-Approach-to-Anterior-Cruciate-Ligament-Injuries-Educate-and-Create-Realistic-Expectations.pdf