A 17-year-old male came to clinic for his health supervision visit. He had been injured during the previous football season and had undergone left anterior cruciate ligament (ACL) repair and successful rehabilitation. He had been cleared by physical therapy and his orthopaedic surgeon to play competitive sports again and was looking forward to the next season. The past medical history was otherwise unremarkable and this was his only significant injury.
The pertinent physical exam showed a muscular male with normal vital signs, with no change in weight or height over the previous year. His physical examination was unremarkable except for a well-healed surgical scar.
The diagnosis of a healthy male with a previous ACL repair was made. The teen noted that he had been working very closely with his physical therapist and weight trainer at school. “I know that I can get hurt again because I’m a running back and have to cut in and out and speed up and slow down. But I’ve worked really hard and done everything I’ve been asked to do. I’m excited that I can play again and want to have a great season especially as I’m a senior now and won’t play in college. I’m good but not good enough for that level,” he said. The pediatrician recommended continuing to work with the trainer and do the exercises to keep his knee strengthened and his other balancing exercises. The pediatrician knew that after ACL repair the longer term outcome wasn’t great for athletes but didn’t know any specifics and decided to look up the question.
The anterior cruciate ligament (ACL) “is an intra-articular but extrasynovial collagenous structure with limited healing capacity that originates in the posteromedial aspect of the lateral femoral condyle and crosses into anteromedially to insert anterior into the intercondylar eminence of tibial articular surface.” It plays an important part as a mechanoreceptor particularly as a proprioceptor. Its main role is to prevent excessive anterior tibial translation, limits varus/valgus stress when the knee is in full extension and some rotary movements of the knee.
There are ~120,000 surgeries per year mainly in the teenage and young adult population, with the number of injuries slowly increasing because of athletic opportunities and exposure. This is especially true for girls and young women who have increased risks because of hormones, genetic predisposition, narrower knee notch width and differences in cutting (e.g. change of direction) and landing biomechanics. Females have an increased risk per exposure at 3.8 vs 3.7 for males. Other risk factors for ACL injury include patella alta (high riding patella) or an increased tibial slope. For females the highest risk sports for ACL injury are soccer and basketball, while for males it is football and lacrosse. Potentially a multisport athlete over 4 years of a high school career could have up to 5-10% chance of having an ACL injury.
Most ACL injuries are non-contact mechanisms (70-80%). Usually a deceleration, cutting, jumping or direct impact (e.g. fall) on the knee. Patients having difficulties describing what occurred, but often stating something like “the knee popped out of its socket,” or it “bent the wrong way” (i.e. hyperextended). On physical examination, risk factors which are more likely with an ACL injury include having a popping sensation during the trauma, the knee “giving way”, presence of continuous effusion and a positive anterior drawer test and/or Lachman test. There are also other tests such as the pivot shift test or lever test which can also be used to help determine on physical examination if the ACL is injured. The gold standard for determination though is magnetic resonance imaging of the knee. Prevention programs include strengthening, multiple different types of exercises and “proximal control” exercises to help with biomechanics.
As a reminder:
Anterior drawer test is performed, “[w]ith the patient in supine position, the hip and knee were flexed to 45 and 90 degrees respectively. While the foot [is] stabilized on the examination table and the hamstrings [are] relax[ed], frequent manual gentle antro-posterior forces [are] applied to the proximal tibia, and tibia antero-posterior displacement in flexed knee [is] measured. The degree of displacement was compared with normal side. Displacement of more than 6 mm comparing the opposite side with a soft end point [is] proposed as torn ACL”
“The Lachman test is carried out in relax supine position, the examiner bends the knee to about 15 degrees [with] slightly external rotation. Then, by stabilizing the femur with one hand and putting the other hand behind the proximal tibia at the level of joint line, and then the tibia is pulled forward. In normal response there should be a steady restraint to anterior movement. Anterior displacement of proximal tibia being felt by examiner thumb in a soft or mushy end point [is] associated with positive Lachman test.”
ACL repair surgery is very successful for patients with good rehabilitation. There are various surgical techniques for repair but treatment appears to be more successful if done within 3 months of injury which appears to prevent additional trauma.
However the long-term outlook may not be as good as one would hope. Up to “81% of athletes return to some sport, while 65% return to their pre-injury level, and 55% return to competitive sports. However, only 38% remained at the same level 2 years after ACL [repair].” Depending on the study, the sport, the particular position on a team, the level of competitiveness, and the amount of time after injury, even many highly trained professional athletes often had fewer games, competitive outcomes (games, assists, goals etc.) and career lengths. Long term problems after repair can include injury to contralateral ACL, osteoarthritis, pain or loss of motion. The loss of motion is often more problematic for patients because of loss of function. Once one ACL is injured there is an increased risk of a contralateral ACL injury (4-25x) within 2 years of surgery.
Questions for Further Discussion
1. What are potential complications of other soft tissue injuries?
2. What are potential complications of fractures? A review can be found here
3. What are indications for use of computed tomography or magnetic resonance imaging for orthopaedic injuries?
4. How are posterior cruciate ligament injuries or meniscal injuries diagnosed?
- Disease: Anterior Cruciate Ligament Injury (ACL) | Knee Injuries and Disorders
- Symptom/Presentation: Extremity Problems
- Specialty: Orthopaedic Surgery and Sports Medicine | Physical Medicine and Rehabilitation / Physical Therapy
- Age: Teenager
To Learn More
To view pediatric review articles on this topic from the past year check PubMed.
Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.
Information prescriptions for patients can be found at MedlinePlus for this topic: Knee Injuries and Disorders
To view current news articles on this topic check Google News.
To view images related to this topic check Google Images.
To view videos related to this topic check YouTube Videos.
Kaeding CC, Leger-St-Jean B, Magnussen RA. Epidemiology and Diagnosis of Anterior Cruciate Ligament Injuries. Clin Sports Med. 2017;36(1):1-8. doi:10.1016/j.csm.2016.08.001
Dekker TJ, Rush JK, Schmitz MR. What’s New in Pediatric and Adolescent Anterior Cruciate Ligament Injuries? J Pediatr Orthop. 2018;38(3):185-192. doi:10.1097/BPO.0000000000000792
Sepulveda F, Sanchez L, Amy E, Micheo W. Anterior Cruciate Ligament Injury: Return to Play, Function and Long-Term Considerations. Curr Sports Med Rep. 2017;16(3):172-178. doi:10.1249/JSR.0000000000000356
Makhmalbaf H, Moradi A, Ganji S, Omidi-Kashani F. Accuracy of Lachman and Anterior Drawer Tests for Anterior Cruciate Ligament Injuries. Arch Bone Jt Surg. 2013;1(2):94-97.
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa