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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 10  |  Issue : 3  |  Page : 197-203

Incidence and risk factors associated with knee injuries among active-duty military personnel in Saudi Arabia


1 Department of Physical Therapy, Prince Sultan Military College of Health Sciences, Dhahran, Saudi Arabia
2 Department of Physical Therapy, College of Applied Medical Sciences, Imam Abdulrahman Bin Faisal University, Saudi Arabia
3 Vice Deanship of Postgraduate Studies and Research, Prince Sultan Military College of Health Sciences, Dhahran, Saudi Arabia

Date of Submission10-Nov-2020
Date of Acceptance27-Oct-2021
Date of Web Publication6-Dec-2021

Correspondence Address:
Alexander Woodman
Vice Deanship of Postgraduate Studies and Research, Prince Sultan Military College of Health Sciences, King Fahad Military Medical City, Al Amal, Dhahran 34313
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sjhs.sjhs_243_20

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  Abstract 


Background: The numbers of musculoskeletal injuries and related risk factors are high, especially in military representatives, since they perform constant physical activities. One of the most common injuries is the knee injury. Although there are many studies relating to knee injuries in the military personnel, none of them have been conducted to estimate the incidence of this injury in the Kingdom of Saudi Arabia. Objectives: This study aimed to explore the incidence of knee injuries and risk factors among the military personnel on active duty in Saudi Arabia. Materials and Methods: This study included n = 2230 patients with knee injuries with a mean age 42.73 and standard deviation ± 16.343 from military branches of the Kingdom of Saudi Arabia (KSA) between 2010 and 2016. Data were collected from Saudi military hospitals and statistically analyzed using descriptive statistics and regression models. During the study, no injuries aggravations of existing injuries or conditions were reported. Results: The frequency distribution showed that anterior cruciate ligament (ACL) injuries were the most common of knee injuries (45.2%) followed by meniscus injury (24.9%) and internal derangement (10.1%) with an incidence rate 4.57, 0.25, and 0.10 respectively. Chi-square test revealed that sports are the most significant factor relating to all knee injuries (30.5%), followed by twisting injuries at 25% (P = 000). Conclusion: Future studies are recommended to generate effective measures to reduce the influence of preventable risk factors, such as sports and related physical activities, that contribute to knee injuries.

Keywords: Injuries, knee injuries, military service personnel, military, Saudi Arabia


How to cite this article:
Albishri SF, Ahmad R, Al Zahrani EM, Jebakumar AZ, Woodman A. Incidence and risk factors associated with knee injuries among active-duty military personnel in Saudi Arabia. Saudi J Health Sci 2021;10:197-203

How to cite this URL:
Albishri SF, Ahmad R, Al Zahrani EM, Jebakumar AZ, Woodman A. Incidence and risk factors associated with knee injuries among active-duty military personnel in Saudi Arabia. Saudi J Health Sci [serial online] 2021 [cited 2022 Jan 26];10:197-203. Available from: https://www.saudijhealthsci.org/text.asp?2021/10/3/197/331776




  Introduction Top


Musculoskeletal system injuries are common within the military personnel. The treatment of these injuries is time-consuming and challenging.[1],[2],[3] The process of rehabilitation prevents participation in military service. In addition to the adverse effect of injuries on the health of military personnel, the incidence of these injuries cannot easily be predicted and prevented.[1],[2],[3]

The military personnel has to maintain optimal fitness levels. They participate in physical activities: recreational team games, marching, and running to sustain the required fitness levels. While accomplishing these tasks, the risk of injuries related to the musculoskeletal system is high, of which the most common is the knee injury.[1],[4]

The incidence of knee injuries among military personnel is multifactorial, such as age, gender, type of sports, body mass index (BMI), flexibility, as well as overuse of the knee: muscle strength and stability, particularly the hamstring ratio to quadriceps strength muscle mass. Knee injuries represent the most significant part of injuries in the lower extremities. It is noteworthy that the number of studies on the incidence and risk factors for injuries of the musculoskeletal system corresponds to the number of studies on knee injuries.[1],[4],[5] These injuries and restrictions negatively affect military personnel's further operational productivity and sometimes impede military training and operations.[4],[5]

Abt et al. reported that around 50% of injuries among special operational forces occurred in the lower extremities, of which about 23.1% was accounted for knee injuries.[6] Kuikka, et al., in their study relating to the occurrence of knee injuries in sports, highlighted the most common types of knee injuries. Thus, according to their study, these injuries were as follows: the injury of anterior cruciate ligament (ACL) (20.3%), medial meniscus tear (10.8%), the chondral lesion (10.6%), medial collateral ligament (MCL) tear (7.9%), contusion damage arising from trauma (5.5%), lateral meniscus tear (3.7%), and patellar dislocation (3.3%).[5] The authors reported that approximately half of all knee injuries occur during physical activity.[5] Males below the age of 30 were more likely to experience knee injuries. Individuals below the age of 20 had a higher chance (84%) to experience a patellar dislocation than those aged 40 or above. A lower military rank increases the risk of patellar dislocation. For instance, among junior army officers, the rates were higher than in senior positions by a ratio of three.[2],[5]

Hsiao et al. (2010) studied the incidence of acute traumatic patellar dislocation among military service members in the U. S. for 10 years. About 930 cases were reported annually. The incidence rate was 0.69 per 1000 person-years in the risk group, where the risk of men's injury was lower than that of women, and the incidence rate per 1000 person-years was 0.39 and 0.63, respectively.[2] Earlier in 2009, Kuikka et al. stated that military persons aged between 15 and 25 years had the highest rates of risk of a knee injury. Meniscal tears represented 15% of all knee injuries. The authors indicated that young male army personnel reported a lower incidence rate of patellofemoral pain syndrome (PFPS) than that of females. They further noted that it is an injury that can be a result of sporting activities.[7]

This statement was further supported by Kang et al. and Boling et al. They reported that PFPS was mainly common among physically active people, active-duty military personnel, and particularly among those between the age of 15 and 30. For example, it was noted that the rate of this injury was 70% among individuals aged between 16 and 25 in a medical clinic specializing in sports-related injuries.[3] The incidence rate of this injury was higher in females than males, 19.6% and 7.4%, respectively. Due to the extensive physical requirements among military personnel, PFPS is prevalent at rates between 4% and 17%.[3],[8]

Various factors are influencing the relatively high incidence of ACL injuries among active-duty military service personnel compared to other knee injuries, such as meniscus injuries, posterior cruciate ligament, and MCL.[9],[10] Of particular importance to the etiology of ACL injuries is the anatomy of the knee joint. In addition to the anatomic features of the knee joint, existing literature indicates that neuromuscular factors are also significant predictors of ACL injuries.[10] The anatomical risk factors relating to ACL injuries include a smaller femoral intercondylar notch width, increased slope of the tibial plateaus, and increased anterior-posterior knee laxity, as well as the relevance of quadriceps to hamstring strength ratio as a possible predictor of ACL tears.[9],[10] These anatomical risk factors are more specific for females than for males, this can explain the gender disparity in ACL injuries between males and females.[3],[8],[10]

Neuromuscular risk factors, such as knee extension during deceleration, lateral trunk motion, as well as posterior weight distribution, further enhance the effect of the anatomical risk factors. These neuromuscular risk factors are particularly significant among military service members because they are quite common in sports and physical exercises and activities that are routinely undertaken by active-duty military personnel.[3],[8],[9],[10] Dry weather conditions can increase risk factors of knee injuries.[9] Several scholars have suggested that footwear design may also influence the development of ACL injuries.[11] Thus, in a review by O'Malley et al. (2015), footwears with longer cleats around the periphery and shorter inner cleats were associated with a high risk of ACL injuries. Although interventions to address these factors have been developed, their effectiveness has not been confirmed to this point.[9]

There is a significant association between the risk of knee injuries and body mass index (BMI).[12] The incidence of such knee injuries as osteoarthritis (OA), meniscectomy, and ACL increases with the rising rates of individuals' BMI.[13],[14] Flexibility is considered one of the decisive factors for soldiers participating in military training, sports, and other physical activities.[15] American College of Sports Medicine defined flexibility as “the ability to move a joint through its complete range of motion.” The flexibility degree may affect the incidence of injuries, specifically knee injuries. Hence, flexibility can cause stress on a joint, including that of the knee.[15] Earlier, Mohammadi et al. reported that physical fatigue of military personnel due to multiple and strenuous physical exercises is one of the risk factors associated with knee injuries.[16]

Although there are many studies relating to knee injuries in the military personnel, none of them has been conducted to estimate the incidence and the prevalence of this injury among the Saudi military personnel. This indicates a gap in the research relating to risk factors and the incidence of knee injuries in Saudi Arabia. This study aimed to explore the incidence of knee injuries and risk factors among the military personnel on active duty in Saudi Arabia.


  Materials and Methods Top


Research design

A retrospective cohort study was selected as a type of research. The study examined the incidences and risk factors associated with knee injuries among military personnel on active duty at four military branches in the Kingdom of Saudi Arabia (KSA): land forces, air forces, naval forces, and air defense forces. The time frame of the study was between 2010 and 2016.

Data collection methods

The data collection process has involved the extraction of data from the available medical records of military hospitals. This extraction was facilitated by a precise sheet accurately designed by the principal investigator to address the study's objectives. The sheet included such variables as age, military unit, diagnosis, and the cause of injury. The sheet also included data used for hospitalization, summarized by major diagnostic categories at the seven-digit level, using the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) to record every patient's experience at military treatment facilities and through outpatient referrals, since most recent studies on knee injuries among active-duty military personnel have been done using ICD as well.

The international statistical classification of diseases and related health problems

The ICD-10-CM classification consists of approximately 14,400 distinct codes and has the tools that allow the addition of new entries. The use of ICD-10-CM sub-classification allows the development of more than 70,000 new codes. The system uses alphanumeric codes for the precise identification of diseases and associated problems.[17] The use of the ICD-10-CM classification in this study was instrumental in facilitating the extraction of relevant data from the medical records of each hospital that agreed to participate in the research.

Data collection procedures

The data collection process began with obtaining specific permissions from the corresponding medical authorities. The PI obtained relevant ethical and security approvals and sent them to military hospitals of the KSA. Only nine out of 13 military hospitals agreed to collaborate. Nine hospitals requested their medical records divisions to facilitate the data collection process.

Statistical analysis

Data analysis was done using SPSS version 23.0 (SPSS Inc., Illinois, U.S.A.). The main factors were the incidence of knee injuries per year (2010-2016) and risk factors associated with knee injuries. The incidence rate was calculated by dividing the total number of incidences of a specific knee injury by the total number of knee cases and expressing the rate per 100 person-years. Correlation between the incidence of knee injuries and various risk factors was evaluated by using a multivariate regression model. This model was applied to estimate the rate of knee injuries per 100 person-years with age, the cause of injuries, and the military unit. The association between diagnosis and causes of injuries was tested using the Chi-square test.


  Results Top


The study explores the incidence and risk factors, and causes of knee injuries among active-duty military personnel in the KSA. This retrospective cohort study extracted data on the incidence of knee injuries from nine military hospitals over 6 years, from 2010 to 2016. A total of n = 2230 patients with knee injuries were studied with a mean age of 42.73 years and standard deviation ± 16.343 [Table 1].
Table 1: Descriptive statistics by age

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The frequency distribution [Figure 1] shows that ACL injuries accounted for the majority of knee injuries in the military personnel at 45.2% (incidence rate of 4.57) of the total (n = 2230) patient population. Other knee injuries with notable incidence include meniscus injury (24.9%) (incidence rate of 0.25) and internal derangement (10.1%) (incidence rate 0.10); internal derangement can also relate to a torn cruciate ligament or a torn meniscus. The incidence of the other diagnoses was negligible with dislocation knee, MCL, and Osgood–Schlatter knee, showing only 0.1%.
Figure 1: The frequency distribution of ACL injuries in military hospitals

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Sports-related factors were the most significant, accounting for 30.5% of all knee injuries [Figure 2]. Twisting injuries (25%) followed after sports injuries. If the twisting occurred as a result of sports activities, the injury was considered a sports injury. Additional risk factors were age (3.9%), falls during daily routine (3.9%), and infection (0.7%).
Figure 2: Factors associated with knee injuries

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The overall incidence of knee injuries by military unit indicated that most knee injuries at 79.7% affected military service members whose specific military units were undetermined cause (unknown). Of those who reported a military unit, 14.2% were from armed forces, 4.8% air defense personnel, and 1.3% naval forces. Analysis [Table 2] revealed a Chi-square = 3931.62; P = 0.000 signifying a highly significant difference (since P < 0.05) between diagnosis and cause of injuries using Chi-square test.
Table 2: Parameter estimates of data from military hospitals

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  Discussion Top


In this retrospective cohort study, the overall incidence and specific types of knee injuries have been studied and calculated for each military hospital. ACL injuries had the highest incidence rate among the military personnel (45.7%, n = 2230). The rate of a meniscus injury was also significantly high (24.9%, n = 2230). Individual incidence rates for each hospital have been determined, as well as the three significant incidence rates for each hospital. This study also revealed significant knee injuries among military people at the age of 18–60 years. There was no association between the incidence of knee injuries and the age in the current study. In addition, there was an association between knee injuries and the cause of injuries reported by applying Chi-square tests. We found the odds ratio with confidence intervals (CIs) using multiple regression between the dependent variable (knee injuries) and the independent variables, such as age, cause of injury, and military unit.

The evidence from this study displayed that ACL and meniscus injuries were the most frequent prevalent knee injuries affecting military service members in the KSA: 45.2% of all knee injury cases among military personnel were affected by ACL, and 24.9% of the cases were affected by meniscal injuries. These findings are consistent with several previously published studies on knee injuries.[18] Rezasoltani et al. conducted a similar study among Iranian armed forces and reported that ACL injuries were the most common knee injuries followed by meniscus injuries.[19]

However, Kuikka et al. reported slightly different findings. In their retrospective study, Kuikka et al. reported that patellar dislocation was the most common type of knee disorder with an incidence rate of 3.1 per 1000 person-years, followed by meniscal injuries (2.2 cases per 1000 person-years). Jones et al. also reported a higher incidence of meniscal injuries (8.2 cases per 1000 person-years), since females were included in the population sample.[20] There is a gap in this study since it primarily calculated the incidence of meniscus problems without comparing it to other knee injuries, such as ACL, as there in some cases, there is a high probability of having both ACL and meniscal damage.

It is also important to note that although the overall results of the study have indicated that ACL and meniscus injuries were the most common diagnoses, some study locations (hospitals) reported contradictory results. For instance, data from the Sharourah and Khamis Mushait hospitals showed that the most common knee injuries were fractures of the patella, amounting to n = 16 (50%) and n = 126 (36.5%). Moreover, only data from 2015 to 2017 were available at Sharourah hospital compared to the 2010–2016 period in the other study locations.

Another contradictory finding in this study was noted at Hafr Albatin and Jeddah hospitals where meniscus injuries were the most common knee disorders accounting for 33% (n = 80) and 50% (n = 34), respectively. The number of studied subjects in these hospitals was lower than average compared to 252 patients per hospital (total sample n = 2230 in all the nine hospitals). The physical training program was almost the same for the entire sample since all officers and soldiers graduated from the same military college and the same military institutes, where there is not much difference in the physical training curriculum. However, the results from Hafr Albatin and Jeddah hospitals were consistent with the studies of Jones et al. (2012).[20] They reported high incidence rates of meniscal injuries among military officers at 8.2 and 10.08 per 1000 person-years. The results from the studies conducted in Taif hospital reported considerably lower incidence rate of ACL disorders and a higher incidence of OA of the knee, accounting for 36.9% of all diagnosed cases of knee injuries. Although OA is not an injury, for this study, researchers distinguished OA as a separate condition that can affect ACL. Still, it should be noted that a history of ACL injuries influences on the development of OA, which, in turn, indicate that the high rate of knee OA may be attributed to the previous history of knee injuries.[13],[18]

Causes of knee injuries

It was found that sports and related activities (30.5%) contributed to the majority of causes of knee injuries among military service members, taking into consideration the diagnosis versus the cause of injury cross-tabulation [Figure 2]. Further, it was found that the involvement in sports activities was a significant risk factor for the development of ACL injuries (P = 0.000), patella fracture (P = 0.000), and meniscus injuries (P = 0.000). Since the sports category is broad and not very specific, it does not tell us much about the causes of injuries. Twisting injury (25%) was the second-most significant factor of knee injuries among this sample. These findings were consistent with Hauret et al. (2015), who reported that 52% of injuries' causes among the military personnel were exercises and sports-related activities.[21] Kuikka et al. and Jones et al. acknowledged the influence of sports on the incidence of musculoskeletal injuries.[7],[20] Alternative studies on the risk factors leading to knee injuries indicated age as one of the decisive factors.[5],[22],[23],[24] However, the results of the current study indicated that age was not a significant risk factor for the development of the two most common knee injuries (ACL and meniscus injuries) among the study sample. The age factor in the development of ACL indicated a P value of 0.195 (95% CI: 0.956–1.009). This implies that age is not a significant risk factor for sustaining knee injuries. Similarly, the influence of age was not statistically significant on the diagnosis of meniscal injuries among sample study, P value of 0.315 (95% CI: 0.958–1.013). Thus, the findings of the current study are contrary to those of Jones et al., Pihlajamäki et al., Kuikka et al., and Gordon et al.[5],[20],[21],[22],[23] Still, in the current study, the age factor was significantly associated with fracture of the patella (P = 0.01) and knee dislocation (P = 0.038).


  Conclusions Top


This study revealed that ACL injuries followed by meniscal injuries were the most common knee injuries among active-duty military personnel in the KSA. Sports activities were commonly cited as the cause/risk factors influencing the incidence of knee injuries. The outcomes of sustaining musculoskeletal injuries among military personnel are not limited to the cost of treatment. It also includes time spent on treatment and rehabilitation. The injuries negatively influence on the operational productivity and military training by preventing military readiness due to time spent out of service during treatment and rehabilitation. Information should also be collected on the data of the time spent in rehabilitation, away from the active duty as a result of ACL injuries, since any patient with ACL needs time to return to daily activities. However, there is a lack of knowledge about how many days (weeks) are required on average for the rehabilitation process. Likewise, the ACL injury (which is the most common knee injury) is a predictive factor for leading to chronic conditions, such as knee OA. This increases the number of lost-duty days, which prevents participation in particular service roles and presents a significant challenge in the military service.

ACL injury among active-duty military personnel is a predictive factor causing chronic conditions, including knee OA. Although there are proper and qualified rehabilitation methods in military hospitals of Saudi Arabia directed by qualified physiotherapists, in most cases, patients do not follow the processes and treatment plan. Future studies are recommended to generate effective measures to reduce the influence of preventable risk factors, such as sports and related physical activities, that contribute to the development of knee injuries, as sports category is broad and not very specific. Accordingly, it is recommended to establish effective measures to reduce the impact of modifiable risk factors, such as sports and related factors, that contribute to the development of knee injuries and develop strategies for reducing risk factors for knee injuries, ways to minimize its effects, and prevent injuries. As such, this study can be seen as a hypothesis-generating study, which supports future research efforts to be redirected to possible alternative factors leading to an ACL injury, for example, those with a BMI >30, the influence of wrong shoes (standard-issue boots versus joggers versus other), hard-playing fields compared to grassy areas, fitness before exercise or sports during development, and cultural attitudes toward physical activity and injuries in subsequent years. Furthermore, based on the results of this study, the authors would recommend for the health informatics management (coding system) to add subcategorize, for instance, sports to football, sprinting, running, and fireman's carry.

The quality and specificity of the diagnoses should be improved. In addition, there may be a significant coincidence between the various actual pathologies affecting the knee and the final diagnoses, as recorded. These issues should be considered as a matter of discussion, and not assume that all health care providers know what they are looking at. If not, they are recommended to undergo a particular training program to recognize and diagnose musculoskeletal system injuries precisely. Furthermore, such factors should be considered as the effect of poorly supporting shoes (lack of support for the medial longitudinal arches of the feet), the relevance and contribution of flat feet to injuries, physical activity in childhood, and the influence of BMI (high BMI) to the likelihood of injury. All these points should be informed and recommended to health care providers. To conduct future results-oriented studies, the health care providers should collaborate with the hospital staff responsible for the ICD coding system and provide more detailed information about each patient.

Study limitations

Based on the study, a significant challenge was identified, as data were collected in only nine out of 13 military hospitals. The remaining four lacked sufficient capacity to accommodate the ICD-10-CM coding system. Some military hospitals have already adapted to the updated ICD-10-CM system, most of the medical facilities are still using the outdated ICD-9-CM code system, which might potentially hinder future research that will rely on the use of the new classification. The way of knee injuries coding by ICD-10-CM was not the same in all hospitals.

The other limitation of this study was the study sample. All participants were males as females in the KSA are not recruited to serve in the military due to cultural issues. The PI was unable to study the effect of gender as a risk factor of knee injuries.

One of the risk factors that was intended to be studied is whether serving in a particular military unit can influence the incidence of knee injuries. However, only three hospitals out of nine consider the type of military unit while coding different types of knee injuries, which was another limitation for more precise analysis.

Acknowledgments

The authors thank all research participants and military hospitals of the KSA who gave their acceptance to participate in this research.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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