sustain an ACL injury than boys (Joseph et al., 2013). In girls, the highest per-season injury risk levels are in gymnastics, soccer, basketball, and lacrosse (Agel, Rockwood, & Klossner, 2016; Gornitzky et al., 2016). In boys, the highest injury risk levels per season are in American football, lacrosse, and soccer (Gornitzky et al., 2016). More than 127,000 ACL reconstructions are performed annually, making it the sixth most common orthopedic procedure in the United States (Hughes & Watkins, 2006; Kim, Bosque, Meehan, Jamali, & Marder, 2011), although rates are rising. From 2002 The ACL originates on the medial side of the lateral femoral condyle and runs through the intercondylar fossa to insert onto the medial tibial eminence (Figure 1). It can be divided into two functional bands, the anteromedial and posterolateral bundles (Petersen & Zantop, 2007). These two bands play different roles, depending on the degree of knee flexion. The anteromedial bundle remains taut throughout the full degree of knee range of motion (ROM), with increased tightening near full flexion (Amis & Dawkins, 1991; Sapega, Moyer, Schneck, & Komalahiranya, 1990). The posterolateral bundle is taut in full extension and in deep flexion but slackens throughout the midrange of motion. The ACL is the primary restraint to anterior translation of the tibia relative to the femur and a major secondary restraint to internal rotation, particularly when the joint is near full extension (Duthon et al., 2006). Normal knee arthrokinematics is maintained with the ACL, along with the posterior cruciate ligament (PCL), through the four-bar linkage system (Müller, 1983). The four-bar linkage system is a model of the knee in which the ACL and the PCL are depicted as rigid bars connecting to the femur and tibia. The restraints of these ligaments help to control roll and glide in the knee joint throughout a full ROM. Damage to the ACL can disrupt this system, resulting in aberrant motion during activity.
to 2014, the overall rate of ACL reconstruction increased 22% in the United States; adolescents (age 13 to 17 years) incurred the highest absolute rates, which increased 37%, 107% and 63% during the study period for isolated ACL reconstruction, ACL reconstruction with meniscal repair, and ACL reconstruction with meniscectomy, respectively (Herzog et al., 2018). In Australia from July 2000 to June 2015, the annual incidence of ACL reconstruction increased 43% including an astonishing 74% among those under 25 years of age (Zbrojkiewicz et al., 2018).
FUNCTIONAL ANATOMY
Figure 1: Knee Anatomy
Note . Retrieved from https://www.niams.nih.gov/health-topics/knee- problems/advanced
MECHANISM OF INJURY
● Knee flexion angle less than 30° in combination with higher hip flexion and lower ankle plantar flexion angles from initial contact to peak knee flexion during landing (Carlson, Sheehan, & Boden, 2016) or cutting/pivoting maneuver (Walden et al., 2015). ● Application of a quadriceps force when combined with knee internal rotation A valgus load combined with knee internal rotation. ● Excessive valgus knee loads applied during weight-bearing, decelerating activities. Patients with a noncontact mechanism of injury may demonstrate greater dynamic knee instability compared to those who have contact injuries (Hurd, Axe, & Snyder-Mackler, 2008a).
Damage to the ACL can result from a contact or a noncontact injury. An estimated 70% of ACL injuries result from noncontact mechanisms (Hewett, Myer, & Ford, 2006). Injuries are often reported during activities involving cutting, changing direction, or landing from a jump; landing on the foot instead of the toes and being perturbed before landing both increase the risk of ACL injury (Griffin et al., 2006). Noncontact ACL injuries are likely to happen during deceleration and acceleration motions with excessive quadriceps contraction and reduced hamstrings co- contraction at or near full knee extension (Shimokochi & Shultz, 2008). ACL loading is higher during any of these situations (Shimokochi & Shultz, 2008; Walden et al., 2015):
CLINICAL COURSE
The sequelae of ACL injury include quadriceps strength deficits, neuromuscular dysfunction, biomechanical maladaptations, and the development of knee osteoarthritis (Daniel et al., 1994; Lohmander, Östenberg, Englund, & Roos, 2004). However, because individuals do not respond uniformly to an acute ACL injury, outcomes can vary. Most of those who have had such an injury decrease their activity levels both in the short- and long-term (Ageberg, Pettersson, & Fridén, 2007; Ageberg, Thomeé, Neeter, Silbernagel, & Roos, 2008; Muaidi, Nicholson, Refshauge, Herbert, & Maher, 2007; Neeter et al., 2006; Ristanis et al., 2006; Tagesson, Oberg, Good, & Kvist, 2008). Nonoperative management of patients with ACL-deficient knees can be effective for those who are willing to avoid high- risk activities (Beynnon, Johnson, Abate, Fleming, & Nichols, 2005). However, between 23% and 42% of patients after ACL injury choose to return to high-level activities after nonoperative
rehabilitation (Hurd, Axe, & Snyder-Mackler, 2008b; Kostogiannis et al., 2007). The standard of care followed by most surgeons for ACL injury in the United States for young, active individuals is early ACL reconstruction (Delay, Smolinski, Wind, & Bowman, 2001; Dye, Wojtys, Fu, Fithian, & Gillquist, 1998). Epidemiological studies have found that patients who are male, younger, Caucasian, and of higher socioeconomic status, and who possess private health insurance are more likely to have ACL reconstruction than nonoperative treatment (Collins, Katz, Donnell-Fink, Martin, & Losina, 2013). Younger athletes who wish to return to high- level sports involving pivoting activities are often advised to undergo early ACL reconstruction because of the assumed inevitable knee instability with sports-related activities (Johnson, Maffulli, King, & Shelbourne, 2003; Marx et al., 2003; Myklebust & Bahr, 2005). However, some patients are able to postpone surgery following a period of intense rehabilitation in order to finish out the
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