Introduction
Soccer has a positive effect on health due to its large fans and popularity at all ages [1, 2]. But on the other hand, training and the nature of soccer can cause a lot of injuries [3 ,4]. Physical fitness and physical condition, psychological factors, techniques, team tactics, injuries, and recovery and recovery from past injuries are effective in the optimal performance of this sport [5].
Soccer injuries are more common in the lower limbs, especially the knee joint [6, 5]. Therefore, preventing athletes from getting injured is the most significant task in medicine and health [8, 9]. Despite all preventive measures, severe injuries such as anterior cruciate ligament (ACL) rupture frequently occur in non-collision situations [8]. One of the main mechanisms of knee joint injury is the dynamic valgus of the knee, which has been described as a combination of adduction and internal rotation of the hip joint and abduction of the knee joint [12].
Differences in the kinematic components of the hip and knee joint in such a situation may explain the emergence of various problems with pain in people with mobility impairments [15]. Excessive knee movement in the frontal plane during exercise is a known cause for many acute and chronic knee injuries [16]. Lack of information on the dynamic valgus knee in soccer can not give a comprehensive view to the designers of preventive exercises. Therefore, the present study, considering this, examines the valgus dynamics of the knee in male soccer players with a review approach to existing studies in this field.
Materials and Methods
In this study, research conducted in recent years, especially from 2000 to June 2021, was collected. These articles had were done by searching electronic sources in specialized English and Persian databases of Google Scholar, Science Direct, PubMed, Magiran Database, Jihad University of Scientific Database (SID), and Islamic World Science Citation Database (ISC). Keywords English and Persian equivalent for the search included the following: dynamic knee alignment, dynamic knee valgus, knee joint kinematics, frontal plane knee excursion, dynamic lower extremity valgus, Male/Men soccer player, Male/Men soccer player, Projection Angle.  
Articles were searched first electronically and then manually from the articles published in the mentioned databases. The criteria for entering the research for the selected articles are as follows: they should be in English or Persian, the full text of the article should be available, research should be done on the study of knee valgus dynamics among male soccer players. Exclusion criteria also included studies that did not examine Valgus knee dynamics among male soccer players and examined prevention or rehabilitation programs, as well as women excluded from the search process.
Results
The tools used in the articles found are more than video analysis to perform, one of the tasks such as jumping vines. This jump is one of the tasks to study the dynamic valgus of the knee after simulating different game minutes [22]and radiography [26]. The most significant situations introduced for the knee joint as traumatic situations in soccer, such as tackling, jumping, imbalance after hitting, and landing after jumping, showed the dynamic valgus position of the knee as a dominant movement pattern [21].
Also, after examining and simulating different minutes of the game, it was shown in the 0th and 60th minutes of the game, as well as in the 105th minute of the game, the Valgus angle was at its maximum [22]. Another study reported that anterior cruciate ligament (ACL) injury, which occurs most often in non-collision positions, puts the knee in a defective movement pattern of excessive valgus dynamics [25]. In 3 articles, it had reported that varus situation is more common in adult male soccer players than valgus and valgus situation is more common in women. 
They also reported that male soccer players will be more likely to suffer from varus than Valgus due to the long-term situation in football. Also, the valgus angle position decreases with age, especially in the late stages of puberty, and the person moves towards the varus position [23, 24, 26]. One study reported that the dynamic situation of the knee valgus is more indirectly involved in the occurrence of injury than directly [27].
Discussion
The valgus load was one of the dominant patterns among injury mechanisms [21]. Some studies confirm that anterior cruciate ligament (ACL) injury generally occurs early in knee flexion, with knee valgus loading [16]. It also seems that between 0 and 60 minutes of play due to low body temperature and insufficient muscle preparation, which reduces flexion, and on the other hand, when there is slight flexion in the knee, it increases dynamic valgus, and thus increases the risk of injury during this period [28].
On the other hand, in the last minutes of the game, the risk of injury due to increased valgus angle is likely to increase, which can be due to fatigue, so that muscle fatigue changes the shock absorption capacity, which can put more pressure on inactive structures [29]. The valgus angle decreases with age and in the late stages of puberty [24]. Also, reaching higher stages of puberty is less likely to injure the knee cause it had reported increasing muscle strength and body structures [24].
The three-dimensional position of the body affects the overall tension in the musculoskeletal system and, ultimately, the function [41]. Biomechanical changes due to the direction of the valgus dynamics may affect the loads applied to the joint [18]. For example, improper neuromuscular control leads to the inability of the knee to maintain alignment and adequate absorption of ground reaction force during dynamic activities, which increases knee valgus increases, stress on the ligaments, and leads to their damage [19].

Ethical Considerations
Compliance with ethical guidelines
All ethical principles are considered in this article. The participants were informed about the purpose of the research and its implementation stages; they were also assured about the confidentiality of their information; moreover, they were free to leave the study whenever they wished, and if desired, the research results would be available to them.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions
All authors contributed equally in preparing all parts of the research.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The Vice Chancellor for Education and Research of the Faculty of Physical Education and Sports Sciences of the University of Guilan is appreciated and thanked.



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