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Original article
The common mechanisms of anterior cruciate ligament injuries in judo: a retrospective analysis
  1. S Koshida1,
  2. T Deguchi2,
  3. K Miyashita3,
  4. K Iwai4,
  5. Y Urabe5
  1. 1Faculty of Health Sciences, Ryotokuji University, Chiba, Japan
  2. 2Graduate School of Education, Hiroshima University, Hiroshima, Japan
  3. 3College of Life and Health Sciences, Chubu University, Aichi, Japan
  4. 4Hiroshima College of Maritime Technology, Institute of National Colleges of Technology, Hiroshima, Japan
  5. 5Graduate School of Health Sciences, Hiroshima University, Hiroshima, Japan
  1. Correspondence to S Koshida, Ryotokuji University, 5-8-1 Akemi Urayasu, Chiba 2798567, Japan

Abstract

Background Although high prevalence of anterior cruciate ligament injuries (ACL) in judokas has been reported, there has been very little research concerning events preceding the injury.

Objective To determine the common situations and mechanisms of ACL injury in judo.

Methods A total of 43 cases of ACL injuries that had occurred during judo competition or practice were investigated, using questionnaires with interviews conducted by a single certified athletic trainer who has 20 years of judo experience to obtain information regarding the situation and mechanism in which the ACL injury occurred.

Results The number of ACL injuries when the participant's grip style was different from the style of the opponent (ie, kenka-yotsu style) (28 cases) was significantly greater than when the participant's grip style was the same as that of the opponent (ie, ai-yotsu style) (15 cases; p<0.001). The number of ACL injuries was significantly higher when the participant was attacked by the opponent than when counterattacked or when attempting the attack (p<0.001). In addition, being attacked with osoto-gari was revealed as the leading cause of ACL injury incidence among the participants (16.8%).

Conclusions Grip style may be associated with ACL injury occurrence in judo. In addition, direct contact due to the opponent's attack may be a common mechanism for ACL injuries in judo.

https://doi.org/10.1136/bjsm.2008.051425

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    Judo, one of the Japanese traditional martial arts, is now the most widely practiced martial art in the world. Judo includes at least four technical aspects: throw, hold down, choke and arm lock, each of which could impose large stress on various anatomical structures. In particular, for successful throws, a judoka needs to manipulate the centre of mass of the opponent relative to the base of support, and then make their opponent land on their back, with speed gathered in the fall as a consequence.

    Due to such characteristics injuries in judo may occur anywhere on the body, but some previous studies suggest that the risk of knee injury is greater than that of any other anatomical structure.1,–,6 Based on 4-year epidemiological research in Finland, Kujara et al1 reported that the knee injury accounted for approximately 20% of all injuries in judo. The study of Miyazaki et al4 also showed that 133 out of 145 collegiate freshman judokas had experienced a history of knee injury; 94 of them had also reported multiple episodes of knee injury in the preseason physical examination.

    Although the medial collateral ligament injury is the most common knee injury,4 anterior cruciate ligament (ACL) injury may be the most serious knee injury in judo. In many cases, surgical intervention will allow judokas to return to their previous activity level; this usually requires intensive and long rehabilitation, which may have large negative impacts on their athletic careers. In addition, the risk of osteoarthritis increases regardless of the surgical intervention.7 For these reasons, sports medicine practitioners must focus on developing effective preventive methods for ACL injuries in judo.

    It is necessary to understand the mechanism of ACL injury in specific sports to establish preventive strategies.8 9 With regard to ACL injury occurrence in team sports such as basketball, soccer and team handball, a number of studies have reported that the majority of ACL injuries occurred in noncontact situations such as in-cutting, stopping and jump landing.10,–,14 Based on these findings, neuromuscular training approaches were developed to reduce the risk of non-contact ACL injuries.15,–,17 Because of the characteristics of judo as a martial art, however, we assume that a non-contact mechanism is not the main cause of ACL injuries and that a neuromuscular training approach may not be suitable for prevention. In order to establish an effective preventive strategy for judokas, the events that incite ACL injuries in judo need to be studied specifically. Therefore, the aim of our study was to determine the common situations and mechanisms of ACL injuries in judo.

    Methods

    Participants

    A total of 46 judokas who experienced ACL injury during judo practice or competition from 13 collegiate judo teams and 2 high school judo teams volunteered for the study. The participants had to be able to recall the situation and the events that incited the ACL injury so that he/she could be included in the study. Prior to the study, all participants signed an informed consent form approved by the ethics committee at the Graduate School of Health Sciences, Hiroshima University, Hiroshima, Japan.

    Data collection

    We gathered information on participants' characteristics, injury characteristics and grip styles via a questionnaire sheet (table 1). In addition, we had a single certified athletic trainer with 20 years of judo experience carry out a semistandardised interview to acquire information on ACL injury incidence with regard to the situation, injury mechanism and other details (table 1). To avoid misinterpretation of the information provided in the interview, we also asked the participants to reproduce the situation and movement at the time of the incident as precisely as possible. The interviewer video recorded the reproduced movement and checked whether the information obtained during the interview matched the reproduced movement.

    View this table:
    Table 1

    Questionnaire and interview contents

    Data analysis

    For grip style, in the questionnaire we asked whether the grip side of the participant was the same as that of the opponent (ai-yotsu style) (fig 1A) or not (kenka-yotsu style) (fig 1B). Since the body position changes in relation to the opponent, each grip style will expose judokas to different situations in judo fighting, requiring different skills for successful throws.

    Figure 1
    Figure 1

    Grip styles. (A) Ai-yotsu grip style: a judoka and the opponent have the same grip side; (B) kenka-yotsu grip style: a judoka and the opponent have different grip sides. Informed consent was obtained for publication of this figure.

    The contents of the interview consisted of several categories (table 1): the judoka's behaviour, the injury mechanism and the technique that directly caused the injury. We categorised judoka behaviour into three groups: attempting an attack, being attacked and being counterattacked. Moreover, we categorised the injury mechanisms into four groups: direct contact injury, indirect contact injury, non-contact injury and others. Direct contact, indirect contact and non-contact injuries were operationally defined as contact with the injured extremity, contact with any part of the body except the injured extremity and no contact with the opponent, respectively.14

    Statistical analyses

    All statistical analyses were performed using Microsoft Excel 2003 (Microsoft, Redmond, Washington, USA). We conducted a χ2 test followed by multiple comparisons to determine the statistical differences between categories. Furthermore, we performed crosstabulation analyses to elucidate the interrelation between the participant's behaviour and the technique that directly caused the injury. Statistical significance was defined as an α level of 0.05 in this study. The α level was corrected with the Bonferroni method according to the number of categories.

    Results

    Six participants were excluded from the study as they did not recall or could not explain the precise situation and/or mechanism of the ACL injury incidence. Three of the participants had experienced bilateral ACL injuries. Therefore, we investigated 43 ACL injury incidents in total.

    The mean (SD) age of the 40 participants (23 men, 17 women) at the time of the investigation was 19.7 (1.6) years old. The mean (SD) age of the time of incident was 17.3 (1.3) years old. Therefore, the average duration between the ACL incidents and the investigation was 29.6 (23.6) months. All participants voluntarily reported that they were diagnosed as having ACL rupture by their orthopaedic doctors. In all, 21 cases had complications such as meniscus and/or other ligamentous injuries; 33 of the ACL injury cases were treated with surgical intervention.

    A total of 28 ACL injuries (65.1%) occurred in the kenka-yotsu style (the participant's grip side was different from their opponent's), whereas 15 ACL injuries (34.9%) occurred in the ai-yotsu style (the participant's grip side was the same as their opponent's). The difference in the number of ACL injury incidents between the two grip styles was statistically significant (χ2=13.062, p<0.001) (fig 2).

    Figure 2
    Figure 2

    Comparison in the number of anterior cruciate ligament (ACL) injury occurrences between the ai-yotsu and kenka-yotsu grip styles.

    A total of 29 ACL injury incidents occurred when the participant was being attacked (67.4%), whereas 8 cases (18.6%) occurred when the participant was being counterattacked and 6 cases occurred when the participant was attempting an attack (14%). The ACL injury occurrence when being attacked was significantly greater than when being counterattacked and when attempting an attack (χ2=22.651, p<0.001) (fig 3). In all, 36 cases of direct contact injury occurred (79.1%), whereas 7 cases of indirect contact injury occurred (20.1%). No noncontact injury was observed in the investigation. The χ2 test was performed after the indirect and non-contact mechanism categories were combined. The result showed that direct contact injury was significantly greater than the other two mechanisms (χ2=36.563, p<0.001) (fig 4).

    Figure 3
    Figure 3

    Comparison in the number of anterior cruciate ligament (ACL) injury occurrences within the categories of judoka behaviour.

    Figure 4
    Figure 4

    Comparison in the number of anterior cruciate ligament (ACL) injury occurrences within the categories of injury mechanism.

    With regard to the results of the crosstabulation analysis between the judoka's behaviour and the technique that directly caused the ACL injury (table 2), we found ACL injuries occurred in the following situations: the participant was attacked by osoto-gari (fig 5) (8 cases, 18.6%), the participant was attacked by kosoto-gari (gake) (fig 6) (6 cases, 14.0%), the participant attempted tai-otoshi (fig 7) (5 cases, 11.6%), the participant was attacked by harai-goshi (fig 8) (5 cases, 11.6%) or kouchi-gari (gake) (fig 9) (4 cases, 9.3%), the participant was counterattacked by ura-nage (fig 10) (4 cases, 7.0%), the participant was counterattacked by kosoto-gari (gake) (fig 11) (3 cases, 7.0%) and others (7 cases, 16.3%).

    Figure 5
    Figure 5

    A typical presentation of anterior cruciate ligament (ACL) injury incidence due to being attacked with osoto-gari: (A) the opponent (right) tries to break the balance of the participant (left), (B) the opponent's leg makes contact with the participant's leg, (C) and the opponent applies rotational force with the action of their upper body and throws the participant. Informed consent was obtained for publication of this figure.

    Figure 6
    Figure 6

    A typical presentation of anterior cruciate ligament (ACL) injury incidence due to being attacked with kosoto-gari (gake): (A) the opponent (right) steps behind the participant (left), (B) the opponent's leg makes contact with the participant's leg, (C) and the opponent applies rotational force with the action of their upper body and throws the participant backward. Informed consent was obtained for publication of this figure.

    Figure 7
    Figure 7

    A typical presentation of anterior cruciate ligament (ACL) injury incidence due to attempting tai-otoshi: (A) the participant (front) tries to break the balance of the opponent (back) with the action of their upper body. Simultaneously, the participant starts turning herself to fit the body for the throw, (B) the participant keeps turning herself and steps with the right leg to the lateral side to make the opponent trip, (C) and the opponent's body applies valgus stress to the participant's knee. Informed consent was obtained for publication of this figure.

    Figure 8
    Figure 8

    A typical presentation of anterior cruciate ligament (ACL) injury incidence due to being attacked with harai-goshi: (A) the opponent (right) tries to break the balance of the participant (left), (B) the opponent's leg makes contact with the participant's leg. Simultaneously, the opponent applies rotational force with the action of their upper body, (C), and the opponent throws the participant. Informed consent was obtained for publication of this figure.

    Figure 9
    Figure 9

    A typical presentation of anterior cruciate ligament (ACL) injury incidence due to being attacked with kouchi-gari (gake): (A) the opponent (left) steps forward to place her body position properly, (B) the opponent's leg makes contact with the participant's leg. Simultaneously, the opponent applies direct force to the participant's knee, (C), and the opponent throws the participant. Informed consent was obtained for publication of this figure.

    Figure 10
    Figure 10

    A typical presentation of anterior cruciate ligament (ACL) injury incidence due to being counterattacked with ura-nage: (A) the participant (right) tries to throw the opponent although the balance of the opponent is not broken, (B) the opponent holds the participant's body and tries to counterattack backwards, (C) and the opponent throws the participant. Informed consent was obtained for publication of this figure.

    Figure 11
    Figure 11

    A typical presentation of anterior cruciate ligament (ACL) injury incidence due to being counterattacked with kosoto-gari (gake): (A) the participant (right) tries to throw the opponent although the balance of the opponent is not broken, (B) the opponent holds the participant's body and tries to counterattack by sweeping the participant's leg, (C) and the opponent throws the participant. Informed consent was obtained for publication of this figure.

    View this table:
    Table 2

    Crosstabulation analysis between the judoka's behaviour and the technique that directly caused the injury

    The result of the crosstabulation analysis between grip style and the judoka's behaviour revealed that being attacked in ai-yotsu style resulted in 17 injury cases (39.5%), being attacked in kenka-yotsu style, 12 cases (27.9%), being counterattacked in kenka-yotsu style, 8 cases (18.6%) and attempting attack in kenka-yotsu or ai-yotsu style, 3 cases. However, there was no case of injury being caused by counterattack in the ai-yotsu style (table 3).

    View this table:
    Table 3

    Crosstabulation analysis between the judoka's behaviour and grip styles

    Discussion

    The most commonly reported mechanism for ACL injuries in judo was direct contact to the lower extremity. Our result also indicates that being attacked by an opponent with osoto-gari, kosoto-gari and harai-goshi may be common causations of ACL injuries in judo. In the interviews, all participants who were injured by being attacked with osoto-gari reported that they had felt the valgus collapse in the knee joint at the time of incident. Most participants also reported that the opponent forcefully rotated the participant's upper body on the leg, as is shown in fig 5.

    Osoto-gari, kosoto-gari (gake) and harai-goshi have similar technical characteristics. These techniques are executed by a sweeping leg making direct contact. In the preparatory phase of the throw, the centre of mass of a judoka who is attacked needs to be moved in a medial–lateral direction, resulting in a shift of body weight to one leg.18 19 Simultaneously, the judoka who attacks needs to place his body properly for a successful throw.19 In the case of ACL injury incidents, we speculate that the valgus stress and then the rotational force applied to the participant's leg by the opponent's action in the throwing phase (probably due to the poor skill of balance breaking and/or misplaced body position of the opponent during the preparatory phase) were causative factors.

    Our results also demonstrate that the number of ACL injury occurrences from the kenka-yotsu style was significantly greater than that those from the ai-yotsu style. We speculate that the higher number of ACL injury occurrences from the kenka-yotsu style may be associated with the higher risk of being counterattacked. Although being attacked was the most frequently observed situation of ACL injury incidence, our results demonstrate that all eight cases of ACL injury occurrence due to counterattack were observed in the kenka-yotsu style, whereas no injury occurred with counterattacks in ai-yotsu style. This result indicates that judokas may be more prone to be injured from counterattacks in the kenka-yotsu style than in the ai-yotsu style, which may be related to the difference in the number of ACL injury occurrences between the two grip styles.

    It is noteworthy that most cases of ACL injury when attempting attack (five out of six cases) occurred with tai-otoshi. As is shown in fig 7, the participant attempts to throw the opponent by breaking the opponent's balance forward and placing their leg in front of the opponent's leg to make him/her trip on it forwards. In the event of ACL injury, valgus stress may have been applied to the participant's knee of the leg placed in direct contact on the lateral side. The risk of injury by attempting tai-otoshi appeared to be higher when the judoka's knee joint was in a full or almost full extension position in the preparatory phase. Avoiding this knee position may play a great role in decreasing ACL injury incidence with tai-otoshi.

    Since we conducted the study retrospectively, the reliability of the participant responses to the questionnaire and the interview warrants careful consideration. In this study, however, we instructed the participants to reproduce the situation at the time of their ACL incident and reviewed whether the filmed situation matched the description obtained during the questionnaire and interview. Therefore, the current results should be reliable and should reasonably represent common situations and mechanisms of ACL injury in judo.

    In addition, no ACL injuries were reported when the participant and opponent were in mat positions, though the authors have experienced working with a judoka who experienced an ACL injury in such a situation. A larger sample size may help us to fully describe the common mechanisms of ACL injuries in judo.

    The neuromuscular training programme developed for ACL injury prevention in basketball and soccer may not be suitable in judo; therefore, a different approach may need to be considered. Ettlinger et al20 developed an education programme for ACL injury prevention in alpine skiers to make skiers recognise dangerous situations with an aim to aid injury avoidance, and reported that the rate of ACL injury occurrence in highly skilled alpine skiers decreased through the use of the education programme. In future studies, it may be necessary to develop an ACL injury awareness programme specifically for judo. An education programme may also help judokas recognise and avoid situations of high risk for ACL injury in judo.

    Any particular injury was related to many factors before the actual occurrence of the injury event, which may include age, gender, race, flexibility, previous injuries and somatotype.8 9 21 In particular, a higher rate of ACL injury in female athletes has been reported than that in male counterparts.11,–,13 22 The difference in gender or other individual characteristics may also need to be taken into consideration in developing an effective preventive strategy for ACL injury in judo.

    In addition, the number of ACL injuries in a particular situation may have been manipulated by the history of how often the judokas had encountered the situation in practice and competition. For instance, among judokas who have had greater opportunity to practice judo in the kenka-yotsu style, the risk of ACL injury from the kenka-yotsu grip style may be greater than that from the ai-yotsu style. In order to enhance our understanding of ACL injury mechanisms in judo, we may also need to closely analyse the individual profiles of judokas in practice and competition.

    Conclusions

    Our results reveal that a direct contact mechanism was the main causative factor of ACL injury in judo. Whether the grip style is the same as that of the opponent or not may also be associated with ACL injury occurrence in judo. Moreover, ACL injuries also occurred more frequently when the participant was being attacked by the opponent than when the participant was being counterattacked or when the participant attempted an attack. In particular, being attacked with techniques that use a single limb as a fulcrum (eg, osoto-gari, kosoto-gari and harai-goshi) may be the most common situation for ACL injuries.

    Acknowledgments

    We would like to thank Mr Naotoshi Minamitani, Ms Ryoko Watanabe, Mr Naotake Watanabe, Ms Motoko Matsuda and Mr Kazuya Tanimura for their assistance in data collection.

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    Footnotes

    • Competing interests None

    • Ethics approval Prior to the study, all participants signed an informed consent form approved by the ethics committee at the Graduate School of Health Sciences, Hiroshima University, Hiroshima, Japan.