Anterior cruciate ligament (ACL) injuries are among the most common injuries in sports, specifically basketball. Female athletes aged 14–19 years have the highest incidence of ACL injury [1, 2]. These injuries have, in part, been associated with the nature of the sport, which involves high-speed changes in direction, jump landing, and pivoting, but more specifically, with the particular movement strategies adopted by these female athletes [3]. Levine et al. reported that combinations of anterior tibial shear force, knee abduction, and internal tibial rotation moments may lead to ACL failure [4]. Reportedly, female basketball players adopt more valgus positions on landing than female athletes from other sports, which may, in part, explain their increased risk [5].
On the other hand, studies have shown that individuals with poorer dynamic balance and core stability are more likely to experience lower extremity injuries [6, 7]. Therefore, poor balance is one of the leading causes of injury, especially in the lower extremities. When the knee assumes a valgus position during an activity, the joint is placed in a less stable position and prone to injury [8]. Accordingly, valgus loading reduction is an effective strategy for reducing the incidence of ACL injuries. Therefore, surgery and rehabilitation prevent adolescents from participating in sports activities for a long period, affecting healthy physical development. In addition, regardless of management, the risk of developing osteoarthritis significantly increases after an ACL injury [9, 10]. Thus, adopting urgent measures to correct this abnormality before reaching pathology can be helpful, indicating the need to develop injury prevention programs.
On the other hand, special warm-up exercises are apparently effective at meeting more demands or needs in sports training and reducing the risk of injury [11]. Consequently, given the importance of warm-up and specific exercises for athletes with ACL injuries, the German Knee Society (DKG) has presented a specific training program called Stop-X to correct dynamic knee valgus (DKV) defects, which can be performed by athletes with DKV defects. It has been reported that these training programs can reduce the incidence of knee injuries by up to 27% and ACL injuries by up to 51% [12].
In this respect, Herrington et al. reported that the drop jump knee valgus angle in the left leg on average was reduced by 9.8°, and that in the right leg was reduced by 12.3°; during the jump shot, the knee valgus angle in the left leg showed a mean reduction of 4.5°, and that in the right leg was reduced by 4.3° following 4 weeks of plyometric training on female basketball players [13]. Additionally, Kato et al. reported an improvement from 36.9° to 15.1° in the coronal-plane lower-extremity maximal angles and from 22.5° to 17.1° in the transverse (horizontal)-plane torsion angle following a course of neuromuscular exercises on basketball players [14]. Otsuki et al. evaluated the effect of injury prevention training (including warm-up) on dynamic knee alignment in female basketball players. According to the results, knee valgus motion and the probability of a high knee abduction moment (pKAM) did not significantly differ between the experimental group and the control group, but did increase [15]. In addition, Eslami et al. explored the effect of 8 weeks of Stop-X and FIFA 11 + Kids Warm-Up intervention on proprioception and balance in soccer players with DKV. The study findings suggested that Stop-X exercises are more effective than FIFA 11 + exercises at improving DKV and balance among young football players with knee valgus abnormalities [16].
On the other hand, basketball is a sport that places significant demands on the knee, requiring running, jumping, and cutting movements that can put the players at risk for ACL injuries [17]. Since females are more prone to ACL injuries than males due to an increased knee valgus angle during landing [18], preventing ACL injury is of paramount importance for basketball players, especially female basketball players. However, a literature review has shown that no research has been conducted on the effectiveness of Stop-X exercises on injured basketball players, such as those with DKV. Therefore, this study investigated the effect of the Stop-X injury prevention program on the knee valgus angle and static and dynamic balance in female basketball players with DKV defects.