Injury mechanism of knee medial collateral ligament: An online systematic video analysis

INTRODUCTION

The medial collateral ligament (MCL), one of the main stabilizers of the knee, is also the most injured ligament of the knee.^[1-3] Isolated MCL injuries are common in young men who play contact sports (e.g. soccer, judo, skiing, wrestling, and hockey).^[4] At the same time, increased participation in sports over the years has contributed to the increase in the frequency of these injuries.^[5]

Isolated injuries to the medial side of the knee, especially the MCL, have received little attention in the literature.^[4] This is primarily due to a focus on anterior and posterior cruciate ligaments as well as postero-lateral corner injuries.^[4] Therefore, besides a discernible lack of evidence when looking at knee motion and muscle recovery following isolated MCL injury, there are still some concerns regarding the incomplete or underestimated clinical and radiographic findings of these injuries.^[4,6]

Although these injuries cause loss of time in athletes, low-stage injuries of the MCL are often not reported.^[2,6] Further studies are needed to elucidate the optimal treatment of MCL injuries as the demand for rapid recovery of patients to pre-injury activity levels, whether recreational or professional, is increasing.^[7] The correct characterization of every aspect of injury will help determine the optimum treatment plan.^[5] One of these aspects that can shed light on the treatment planning for MCL injury is knowing the most common injury mechanism.^[2]

One of the methods used to determine an injury mechanism in detail is the video analysis method.^[8] To the best of our knowledge, there is no video analysis study on the mechanism of MCL injury in the literature. In this study, the aim was to determine the body positions related to the mechanism of injury and the maneuvers that caused it by video analysis of isolated MCL injuries. It was hypothesized that MCL rupture in professional athletes develops with a specific injury mechanism. Furthermore, body posture at the time of injury varies in different sports.

MATERIALS AND METHODS

On May 15, 2021, “knee medial collateral injury” and “MCL injury” were entered in a YouTube^® search.^[9] All search results obtained were monitored. All videos found in the search were reviewed and approved by the three study authors. The inclusion criteria were to verify that the video was compatible with the injury, that the video included the foot, ankle, knee, hip, and the whole body at the time of injury, and that image quality was sufficient to detect the mentioned body parts. Exclusion criteria were suspicious injury videos, insufficient images, poor video quality, and additional injuries with MCL. After scanning, 31 videos with 29 injuries were found. One case was excluded because the whole body could not be seen in the video, three cases were due to non-MCL injury, one case due to poor image quality, and three cases were due to accompanying anterior cruciate ligament injury in the video description. The remaining 23 MCL injury videos were included in the study [Table 1]. This methodology has previously been used in recent research.^[10,11]

The injury mechanism was analyzed into two categories non-contact and contact. Contact injuries, on the other hand, were divided into direct and indirect contact injuries. Direct contact injuries are those in which an external force was applied directly to the injured knee, whereas indirect contact injuries are those where the injury occurs without any contact at the knee or other level before or during the injury.^[12]

A video analysis software was not used to examine each part of the video. Therefore, quantitative measurements were not performed. The videos were viewed by slowing them down to 0.25 speed. The above-mentioned authors examined the videos for the following: the presence of contact, play activity at the time of injury (take-off/acceleration, jump descent, jump, stop/turn), body position (neutral, flexion, and extension), body tilt (ipsilateral, contralateral), body rotation (ipsilateral and contralateral), coronal hip position (neutral, abduction and adduction), sagittal hip position (neutral, flexion, and extension), hip rotation (neutral, internal, and external), sagittal knee position (flexion and extension), coronal knee position (neutral, varus, and valgus), sagittal ankle position (neutral, dorsiflexion, and plantar flexion), coronal heel position (neutral, varus, and valgus), and foot position (neutral, pronation, and supination). Videos were evaluated blindly by all three authors. These data were analyzed statistically, and then intra- and inter-observer agreements were evaluated. The common position indicated by at least two observers in the obtained body positions was considered the correct position. In any case, where all observers indicated a different position, the three observers would watch the video together to make a joint decision. However, this did not occur in the course of this study. Intra- and inter-observer agreement was investigated using the Fleiss kappa (k) statistics for categorical data. The inter-observer agreement percentages were calculated by dividing the number of occasions of the complete agreement by the total number of occasions. It was interpreted as follows: <0.00= poor agreement; 0.00–0.20= slight agreement; 0.21–0.40= fair agreement; 0.41–0.60= moderate agreement; 0.61–0.80= substantial agreement; and 0.81–1.00= almost perfect agreement. Statistical significance was set at P < 0.05. SPSS^® version 23.0 was used in the statistical analyses.

RESULTS

Of the 23 injuries included in the study, 22 (95.7%) were male and one was female (4.3%). The right side was injured in five cases (21.7%) and the left side was injured in 18 cases (78.3%). The distribution of activities in which injuries occurred was seven basketball (30.4%), four American football (17.4%), four ice hockey (17.4%), three soccer (13.0%) one water ski (4.3%), one skateboard (4.3%), two-track and field (8.6%), and one wrestling (4.3%).

In 18 cases (78.3%), the injury occurred by contact. Of these, 16 were caused by direct contact (69.6%) and two by indirect contact (8.7%).

In the data obtained from the video recordings, the intra- and inter-observer agreement was substantial (k = 0.790, P = 0.01 and k = 0.743, P = 0.01, respectively). The game activity at the time of injury is summarized in [Table 2] and the features of the video analysis related to the mechanism of injury are summarized in [Table 3].

DISCUSSION

The important findings in this study were that MCL injury occurred when valgus force was applied when the trunk was flexed and turned toward the injured side, the hip was abducted and slightly flexed, and the knee was slightly flexed. In 69.6% of these cases, there was direct lateral contact to the knee. The most common injury occurred as a result of a collision with an opponent or an object.

Isolated MCL injuries are common ligament injuries of the knee and are generally treated conservatively.^[4] However, injuries on the medial side are heterogeneous. The complex anatomy of this region has led to the difficulty of planning with a standard algorithm for treatment. Knowing the MCL anatomy makes it much easier to understand the clinical examination and pathological anatomy and to choose the correct treatment method to obtain a stable knee close to normal function and return to the pre-injury activity levels.^[13] Injury prevention research has been described as a step-by-step process in which information about its causes is systematically collected and used to develop potentially effective intervention methods. It is important to identify the triggering event or mechanism of injury to develop specific injury prevention methods for a particular type of injury in a particular sport.^[8] To know the mechanism of injury is necessary to effectively design specific exercise programs to reduce its frequency.^[8,12] Video analysis in determining the injury mechanism may reveal deficiencies or mislead the mechanisms specified by the previously determined theoretical models.^[10,11] Since the present study is the first video analysis study on MCL injury mechanisms in the literature, it provides valuable information.

The MCL is the main medial stabilizer against valgus stress in the knee and provides resistance against external rotational trauma of the lower extremity.^[14,15] The information in the literature agrees that direct or indirect valgus stress applied to the flexed knee will play a role in MCL injury.^{[2,6,7,16-19]} On the other hand, it is not clear whether the external rotation mechanism accompanies isolated MCL injury.^{[2,3,6,7,16-20]} In the present study, the rate of external rotation of the tibia accompanying the injury mechanism was only 26.1% of the cases. Often the injuries were not accompanied by rotation. One previous study examined the relationship between pronation-type ankle injuries and MCL injuries.^[21] When pronation force is applied to the ankle and subtalar joint, internal rotation and abduction of the tibia occur together.^[22] This event causes valgus and rotational force in the knee joint, which forces the medial-sided structure of the knee, causing valgus knee injury.^[23] In the present study, the foot was in pronation in 39.1% of the cases. This situation was in the form of the foot taking the pronation position while the proximal tibia medialized with the valgus force applied directly to the knee while standing on the ground. Or, when the foot was suddenly placed on the floor while the hip was abducted, valgus strain occurred in the knee while the foot was going to pronation.

MCL injuries mostly occur by contact.^[4,6,20] Lundblad et al. reported 70.4% of contact-related injuries.^[6] A similar rate of injury occurring after contact was determined in the present study. And 88.9% of these were seen after direct contact with the knee from the lateral.

These injuries are common in contact sports such as football, ice hockey, rugby, wrestling, and judo.^[6] Basketball and football were the most common injury groups in this study. And often, there was an injury due to a blow from an opponent during a double fight.

In the prevention of sports injuries, exercise programs, the use of a brace, regulation in sports rules, or the strict application of the rules against some positions by the referees can be counted.^[5,6,24] Considering that the majority of MCL injuries occur by contact mechanism, the use of a brace and sports rules are more important in the prevention of injury. However, the use of a brace may reduce sports performance.^[5] In this case, the sports rules and the strict enforcement of these rules by referees may be important in preventing MCL injury. New developments in brace technology may play a key role against these injuries in the future.

There are several shortcomings of the present study. Factors such as demographic characteristics, characteristics of MCL injury, treatment method, duration, and characteristics of rehabilitation are not known. In addition, the risk factors for these injuries to cause MCL injury is unknown. Furthermore, because injury data are derived from public records, they may not be 100% accurate and it may not be confirmable that every athlete assessed as an isolated MCL injury during the study period suffered an isolated MCL injury or was an isolated injury. However, video analysis of injuries reported on YouTube is an accepted method used to identify different injuries.^[10,11] Another shortcoming can be listed as the limitations in video analysis. Since the videos are uploaded by different people and/or for different purposes, the video quality and camera angles, the distance the image was taken from, and the number of views obtained from different angles were not the same. At the same time, there were amateur camera shots as well as injuries to professional athletes. For this reason, some videos were examined from one angle. Due to the lack of this standardization, joint angles based on injury could not be measured on a video program and thus could not be analyzed quantitatively by pouring into numerical values. Since only the positions at the time of MCL injury were defined, they could be evaluated qualitatively. However, despite these deficiencies, valuable information regarding MCL injuries occurring during professional or amateur sportive activities can be gained as this is the first study to examine body positioning and activities of isolated MCL injuries through video analysis.

CONCLUSION

Isolated MCL injury occurs when valgus force is applied with the trunk flexed and turned towards the injured side, the hip abducted and slightly flexed, and the knee slightly flexed. The majority of these cases occur after a direct blow to the lateral knee.