Knee Injuries
Knee injuries are some of the most common injuries in snow sport athletes, especially in skiers, accounting for approximately one third of all reported injuries.[23,30–32] Soft-tissue injuries account for most reported cases, and the ACL is involved in approximately 50% of all serious knee injuries. As in other sports, noncontact ACL injuries in skiing occur more frequently in females than in males. Ruedl et al[30] found a twofold increased risk for ACL tear in a female recreational skier's nondominant leg. This injury most commonly involved the left leg, because >90% of skiers preferred the right leg as their kicking leg. In addition to soft-tissue injuries, fractures secondary to high-energy trauma also are observed. In children, it is not uncommon to discover Salter-Harris fractures of the distal femur associated with downhill skiing.[33] In adults, the incidence of tibial plateau fracture is on the rise, with lateral plateau fractures being the most common variant.[28]
Multiple proposed mechanisms exist for ACL injuries related to snow sport activity. In a study by Bere et al,[34] 20 videos of World Cup skiers sustaining ACL injuries were analyzed. Three main mechanisms of injury were identified: back-weighted landing, slip-catching, and dynamic snow plowing. The ultimate cause of failure in the dynamic snow plowing and slip-catching mechanisms was knee internal rotation and/or valgus loading. Most injuries (50%) were in the slip-catching category and occurred as the outer ski was reestablishing contact with the snow. The inside ski edge suddenly caught the surface of the snow, forcing the knee into excessive valgus and internal rotation (Figure 2). This combination of valgus and internal rotation loading of the knee is consistent with biomechanical studies simulating ACL injuries in skiers. Other mechanisms have been described, such as valgus and external rotation loading of the knee, as well as the classic phantom foot phenomenon, which occurs as the skier falls backward in between the skis as the inside edge of the downhill ski catches the snow's surface, ultimately resulting in internal rotation of the flexed knee.[28,32] Secondary to the previously described mechanisms, especially valgus load, it is not uncommon to discover concomitant injuries, such as medial collateral ligament sprains, meniscal tears, and even tibial plateau fractures.[28] The previously described mechanisms of injury are unique to skiing and differ substantially from those experienced in other sports. Failure of ski bindings to release as these injuries occur has been noted, as demonstrated in 24.6% of skiers in the series by Koehle et al[32] and in 17 out of 20 skiers in the series by Bere et al.[34] Although ligamentous injuries of the knee tend to occur less frequently in snowboarders than in skiers, experienced snowboarders who perform large jumps and tricks are at risk for these injuries. A proposed mechanism for ACL injury in snowboarders is eccentric quadriceps contraction on a flexed knee while landing on a flat surface, forcing the knee into internal rotation.[7]
Figure 2.
Photographs showing a slip-catch mechanism of injury, causing left knee anterior cruciate ligament injury. A, The skier is out of balance backward and inward during a right-hand turn. B, The skier loses pressure on the outer ski, which drifts away from the body's center of mass. C, The outer ski catches the inside edge abruptly. D, The skier falls backward toward her left. (Reproduced with permission from Bere T, Mok KM, Koga H, Krosshaug T, Nordsletten L, Bahr R: Kinematics of anterior cruciate ligament ruptures in World Cup Alpine skiing: 2 case reports of the slip-catch mechanism. Am J Sports Med 2013;41 [5]:1067–1073.)
Overall, management of knee injuries related to winter sports does not differ greatly from that for injuries related to other sports. Oates et al[35] evaluated the risk for further injury in skiers with native, ACL-deficient, and reconstructed knees. Compared with knees that had intact ligaments, ACL-deficient knees exhibited a 6.2-times higher risk of injury than intact knees did, and reconstructed knees demonstrated a 3.1-times higher risk of injury. Only 13% of the native knees ultimately required surgery, whereas 39% and 41% of the ACL-deficient and reconstructed knees, respectively, required surgery. The authors also found that skiers who were treated with hamstring autograft were considerably more likely to experience rerupture than were those who were treated with patellar tendon autograft.
J Am Acad Orthop Surg. 2018;26(1):e1-e10. © 2018 American Academy of Orthopaedic Surgeons
