With roughly 200,000 professional and around 240 million amateur soccer players, soccer has been recognized as the most popular sport worldwide. Nevertheless, given its rising popularity in society, one must also consider the increasing incidence of injuries as a result. Elite soccer players sustain between 10 and 35 injuries per 1000 competitive playing hours.1 Approximately 80% are traumatic, and 20% are overuse injuries.2 Soccer injuries are more frequent with increasing age of the participants, whereas the incidence of injuries in preadolescent players is low. The incidence of injuries has been found to be higher during competition when compared with practice/training sessions, with some studies showing that 59% of injuries occurred during games.2 Amateur or recreational soccer players sustain fewer injuries than professional soccer players, as one would expect, given both the higher intensity of training and match schedule in professionals.
The ankle is one of the most commonly injured joints in soccer, with some studies suggesting it comprises one-fifth of all injuries sustained during soccer, which is only second to those of the knee.2 Ankle sprains specifically are quite a common occurrence in soccer.3-9 A recent study of an English premier league club showed that over a 4-season period, 20% of injuries were of the foot and ankle with a mean return to sport time of 54 days.10 Of all foot and ankle related injuries, ankle sprains are the most common, followed by bruises/contusions, and tendon lesions. Fractures are very rare (1%) in soccer, but when they do occur they impart a much more extended recovery. During the 2010 Fédération Internationale de Football Association (FIFA) World Cup, ankle sprains were among the most common injuries and approximately half lead to players missing training or competitive matches.5
Knowledge of the biomechanics of both the foot and ankle joints is essential to understand soccer injuries. The ankle joint (talocrural articulation) consists of the distal ends of the tibia and fibula, which form the mortise, and the superior aspect of the talar dome.11 As a hinge joint, the ankle provides 20° of dorsiflexion and 50° of plantar flexion,12 with stability provided by the lateral, medial, and superior ligamentous complexes. The superior articular surface of the talus is narrower posteriorly, which creates a looser fit within the mortise during plantar flexion.11 This decreased stability could help explain why the most common injury in soccer involves a plantar flexion mechanism.13,14 Inferiorly, the talus articulates with the calcaneus to form the subtalar joint. It is at this site that the majority of both foot inversion and eversion occurs. The transverse tarsal joints (Chopart’s joints) separate the hindfoot from the midfoot. Movement of this joint depends on the relative alignment of its 2 articulations: the talonavicular and calcaneocuboid joints. During foot eversion, these 2 joints are parallel to each other allowing supple motion and aiding in shock absorption during the heel strike phase of the gait cycle. With foot inversion, the joints become nonparallel and thus lock the transverse tarsal joints providing a rigid lever needed for push-off.11,12
The ankle joint is stabilized laterally by a ligament complex consisting of 3 individual ligaments, all originating from the lateral malleolus: the anterior talofibular ligament (ATFL), the posterior talofibular ligament (PTFL), and the calcaneofibular ligament (CFL) (Figure 1).11,12,15 The ATFL is the primary restraint to inversion in plantar flexion, and it helps resist anterolateral translation of the talus in the mortise. However, it is the weakest and therefore the most frequently injured of the lateral ligaments. The PTFL plays only a supplementary role in ankle stability when the lateral ligament complex is intact. It is under the greatest strain in ankle dorsiflexion and acts to limit posterior talar displacement within the mortise as well as talar external rotation.13,16 The CFL is the primary restraint to inversion in the neutral or dorsiflexed position. It restrains subtalar inversion, thereby limiting talar tilt within the mortise.
The deltoid ligament complex consists of 6 continuous adjacent superficial and deep ligaments that function synergistically to resist valgus and pronation forces, as well as external rotation of the talus in the mortise.11-13,17 The superficial layer crosses both ankle and subtalar joints. It originates from the anterior colliculus and fans out to insert into the navicular, neck of the talus, sustentaculum tali, and posteromedial talar tubercle. The tibiocalcaneal (sustentaculum tali) portion is the strongest component in the superficial layer and resists calcaneal eversion. The deep layer crosses the ankle joint only. It functions as the primary stabilizer of the medial ankle and prevents both lateral displacement and external rotation of the talus. It originates from the inferior and posterior aspects of the medial malleolus and inserts on the medial and posteromedial aspects of the talus.12,17,18
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