Clinical Review

Knee Injuries in American Football: An Epidemiological Review

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Posterior Cruciate Ligament

The PCL is the primary posterior stabilizer of the knee.61,62 It consists of the anterolateral and posteromedial bundles, named by their insertion on the posterior tibial plateau. The larger, stronger anterolateral bundle is the primary restraint to posterior tibial translation.63

Due to the relative infrequency of PCL injuries, there is a paucity of epidemiological data on sports-related PCL injuries. These injuries in the literature are commonly found due to traffic accidents (45%-57%) or from sports (33%-40%).64,65 According to Swensen and colleagues,1 PCL injuries account for 2.4% of all high school sport knee injuries. In a cohort of 62 knees with PCL injuries, Patel and colleagues66 found football was the most common cause of injury (19.3%).

The most common mechanism of injury in athletes is knee hyperflexion or a direct blow to the tibia in a flexed knee.67 In football, contact mechanisms are the most common. In a 16-year review of the National Collegiate Athletic Association (NCAA) injury surveillance system, the incidence of contact PCL injuries during games were 7.3 times higher than noncontact.68 The most common activity was being tackled, which accounted for 22.9% of all PCL injuries.68

Due to the high energy of these injuries, isolated PCL injuries are rare. In one trauma center’s experience, 96.5% of PCL injuries had an additional ligament injury.64 In that study, injuries to the PCL were associated with posterolateral corner, ACL, and MCL injuries 62%, 46%, and 31% of the time, respectively.64,69

Because isolated PCL injuries are rare, clinicians must rely on a thorough history and physical examination when evaluating athletes with knee injuries. Classification of PCL injuries is based on the amount of posterior tibial translation in relation to the femur with the knee bent to 90°. Grade I is 1 to 5 mm; Grade II, 6 to 10 mm; and Grade III, >10 mm. If there is suspicion of a PCL injury, there should be a very low threshold for magnetic resonance imaging, given the high association with additional injuries.

Natural history of Grade I and II isolated PCL injuries is generally favorable compared to Grade III and multi-ligamentous injuries.70 As a result, isolated Grade I and II PCL injuries are generally treated nonoperatively. Treatment consists of physical therapy with emphasis on quadriceps strengthening. Return to play can be considered as early as 2 to 4 weeks from injury.71 Recent long-term data have shown successful conservative management of Grade I and II injuries with quadriceps strength to 97% of contralateral leg and full range of motion.72 However, there was 11% moderate to severe osteoarthritis in these patients at a mean follow-up of 14.3 years.72 Fowler and Messieh67 managed athletes with 7 isolated complete PCL tears and 5 partial tears nonoperatively, all of whom were able to return to sport without limitation. Parolie and Bergfeld73 managed 25 athletes with isolated PCL tears conservatively. In this study, 80% of athletes reported satisfaction and 68% returned to previous level of play.73 Neither of the aforementioned studies specify the grades of the injuries. Finally, Patel and colleagues66 managed 6 NFL athletes with Grade I and II injuries nonoperatively, and all were able to return to sport.

Treatment of isolated Grade III PCL injuries is more controversial, and no consensus exists in the literature. In an epidemiological study, Dick and colleagues68 found that only 39% of NCAA football athletes underwent surgery for their torn PCLs, compared to 79% of ACL injuries. However, their study makes no mention to the severity of these injuries. Numerous options exist for PCL reconstruction, with no consensus on the preferred method.


Knee injuries are the most common injury in football. Knowledge of the natural history of these injuries, as well as treatment options and expected outcomes, will help treating physicians educate their patients on the optimal treatment and manage return to play expectations.

Am J Orthop. 2016;45(6):368-373. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

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