1. Introduction

The Achilles tendon, renowned as the largest and strongest tendon in the human body, plays an indispensable role in human locomotion¹. It is critical for activities such as walking, running, and jumping, effectively transmitting the powerful forces generated by the calf muscles to the heel².

However, this vital structure is also susceptible to rupture, a significant musculoskeletal injury characterized by a partial or complete tear of the tendon fibers³. Such ruptures can lead to substantial pain, functional impairment, a protracted period of rehabilitation, and considerable time away from both occupational and recreational pursuits⁴.

In fact, Achilles tendon rupture is recognized as the most frequently injured tendon in the lower extremities, underscoring its clinical importance⁵. The injury typically occurs when the tendon is subjected to forces that exceed its inherent tensile strength, often during sudden, forceful, or uncoordinated movements³. This report aims to provide a comprehensive analysis of the global trends in Achilles tendon rupture incidence and to identify the primary factors that contribute to changes in these levels. By examining data from a diverse range of geographical regions, including France, Germany, Italy, Japan, the United States, South Korea, New Zealand, Denmark, Finland, Sweden, Australia, Canada, and the United Kingdom, this analysis seeks to discern overarching patterns in the occurrence of this injury. Understanding these trends and the underlying causes is of paramount importance for developing effective strategies aimed at prevention and for optimizing the clinical management of patients who sustain this debilitating injury. This report will synthesize the available evidence to provide a detailed overview of this significant musculoskeletal concern.

2. Global Trends in Achilles Tendon Rupture Incidence

Epidemiological studies conducted across the world have revealed a notable degree of variation in the reported incidence rates of Achilles tendon rupture. These rates span a considerable range, from 1.8 to 51.3 cases per 100,000 person-years, suggesting that the frequency of this injury may be influenced by a multitude of factors that differ across populations and regions⁶.

In the United States, research indicates an incidence rate ranging between 7 and 40 per 100,000 person-years, with the average annual incidence being approximately 13.4 per 100,000 individuals⁵. In contrast, Japan reported a relatively stable annual incidence of Achilles tendon rupture between 2010 and 2017, with rates fluctuating between 12.8/100,000 and 13.9/100,000⁸. Several countries have observed an increasing trend in the incidence of Achilles tendon ruptures. Sweden, for instance, has seen a significant rise from 28.8 per 100,000 person-years in 2002 to 41.7 in 2021⁹. Similarly, Finland has experienced an upward trajectory, with the incidence increasing from 17.3 to 32.3 per 100,000 person-years between 1997 and 2019¹¹. In North America, Ontario, Canada, reported an increase in the annual incidence density rate from 18.0 to 29.3 per 100,000 person-years between 2003 and 2013¹². Denmark has also documented a statistically significant rise in incidence from 1994 to 2013, with rates ranging from 26.95 to 31.17 per 100,000 person-years¹³. South Korea has shown a similar pattern, with the incidence increasing from 20.75 per 100,000 person-years in 2009 to 26.53 in 2017¹⁴. Germany's data reveals an average incidence of 7.77 per 100,000 person-years between 1991 and 2015, with an increasing trend observed until 2008, reaching a peak of 11.33 per 100,000 person-years⁶. Italy, however, experienced a peak in the incidence of Achilles tendon repair procedures in 2010¹. New Zealand is notable for a high incidence of Achilles tendon rupture among women, primarily linked to their participation in the sport of netball¹⁶. France reports an annual incidence ranging from 5 to 50 events per 100,000 people⁴. Overall, the data suggests a predominant global trend of increasing Achilles tendon rupture incidence, particularly evident in several European countries and North America. Japan's relatively stable incidence during its study period presents a notable contrast to this general pattern. The wide spectrum of reported incidence rates across different countries underscores the potential influence of diverse factors, including variations in study methodologies, population demographics, physical activity patterns, and healthcare systems.

3. The Role of Demographics

Demographic factors such as age and sex have a significant influence on the incidence of Achilles tendon ruptures across the globe. A consistent finding in numerous studies is the higher occurrence of this injury in men compared to women, with reported male-to-female ratios ranging from approximately 2:1 to as high as 5.7:1⁷. For instance, in Japan, 67% of the reported Achilles tendon ruptures occurred in men⁸. The average age of individuals who experience an Achilles tendon rupture typically falls within the range of 30 to 50 years, a period often characterized by active participation in recreational sports¹⁸. In fact, ruptures tend to occur most frequently during the third and fourth decades of life⁸. Interestingly, a bimodal age distribution has been observed for Achilles tendon ruptures, with an initial peak in incidence among middle-aged athletes and a secondary, smaller peak in older, less active individuals¹⁹. This pattern suggests that different etiological factors may be at play across these age groups. However, in New Zealand, the high incidence of Achilles tendon rupture among women, primarily attributed to their involvement in netball, results in a younger average age of injury compared to typical reports¹⁶. Over time, several countries, including Denmark and Finland, have reported an increasing incidence of Achilles tendon ruptures in older populations, particularly those over 50 years of age¹¹. This trend may be indicative of increased participation in physical activities by older adults. In the United States, the most substantial increase in incidence was observed in the 40-59 year age group²¹. These demographic trends highlight the evolving patterns of Achilles tendon ruptures across different age and sex groups worldwide.

4. Sports and Physical Activity as Key Drivers

A substantial body of evidence indicates a strong association between sports and physical activity and the incidence of Achilles tendon ruptures. Many studies report that the majority of these injuries occur during participation in athletic endeavors⁶. Achilles tendon ruptures are particularly prevalent in sports that necessitate jumping, cutting, and sudden kinetic movements, which place considerable stress on the tendon²⁴. The phenomenon of "weekend warriors," referring to middle-aged adults who engage in intense physical activity sporadically, is often cited as a significant risk factor for these injuries³. Furthermore, the increasing trend of older adults participating in high-demand sports is considered a likely contributing factor to the observed rise in Achilles tendon rupture incidence in several countries⁸. The specific sports and activities commonly linked to Achilles tendon ruptures vary across different regions. In the United States, basketball is frequently reported as a common cause²¹. Soccer is a commonly implicated sport in European countries and Canada²³. Badminton is recognized as a frequent cause in Denmark and Sweden¹⁴. Tennis is another sport commonly associated with these injuries across various regions³. Volleyball is noted as a contributing factor in Finland, Canada, and Japan⁷. In New Zealand, netball stands out as a major cause, particularly among women¹⁶. Other sports like floorball in Sweden and American football in the US are also implicated²¹. The increasing involvement of individuals in recreational sports and the rising participation of older adults in physical activities are likely major factors driving the overall trends in Achilles tendon rupture incidence.

5. Other Contributing Factors to Changing Incidence

While sports-related activities are a primary trigger for Achilles tendon ruptures, several non-sporting factors also contribute significantly to their occurrence and the observed changes in incidence levels. Age-related degeneration of the Achilles tendon is a crucial intrinsic factor. Tendon ruptures frequently occur in tendons that have already undergone degenerative changes, which weaken their structural integrity⁸. As people age, the Achilles tendon naturally loses some of its flexibility and may develop tendinosis, a condition characterized by degenerative changes within the tendon tissue that can predispose it to tearing²⁵. Furthermore, individuals with a prior history of Achilles tendinitis, an inflammatory condition of the tendon, have a higher risk of experiencing a subsequent rupture, indicating that a compromised tendon is more vulnerable to injury¹⁸. Certain medications have also been implicated in increasing the risk of Achilles tendon rupture. Fluoroquinolone antibiotics, a class of commonly prescribed drugs, have been associated with an elevated risk of this injury, possibly due to their adverse effects on collagen, the main structural protein of tendons¹⁸. Similarly, while corticosteroid injections are sometimes used to manage pain and inflammation in the ankle area, they can also weaken the surrounding tendons and have been linked to an increased risk of Achilles tendon rupture³. The use of oral or parenteral glucocorticoids is also considered a risk factor¹⁸. Body weight and obesity also play a significant role. Excess body weight places additional mechanical strain on the Achilles tendon during daily activities and physical exertion, potentially increasing the likelihood of rupture¹⁸. Studies have indicated that overweight or obese individuals are more prone to developing Achilles tendinopathy, which, as mentioned earlier, can be a precursor to rupture⁵⁸. The influence of socioeconomic factors on Achilles tendon rupture incidence is less clear and appears to be complex. One study reported a higher incidence of re-rupture in less socioeconomically deprived populations⁶⁰, while another found that patients with Achilles tendinopathy from lower socioeconomic backgrounds might experience poorer treatment outcomes⁶¹. Interestingly, a separate study observed a higher incidence of primary Achilles tendon rupture in less socioeconomically deprived populations, suggesting a potential link with greater participation in sports among these groups⁶². Finally, while the provided snippets offer limited information on occupational risks, it is recognized that abnormal or excessive mechanical loading of the Achilles tendon in certain working environments can contribute to tendon injury⁶³. Further research would be needed to fully understand the extent to which occupational factors contribute to the global incidence trends of Achilles tendon rupture.

6. Trends in Treatment and Their Potential Influence

The management of Achilles tendon ruptures typically involves either surgical repair or non-surgical treatment, often followed by a structured rehabilitation program. Surgical approaches aim to re-approximate the torn ends of the tendon, while non-surgical management usually involves immobilization in a cast or brace to allow the tendon to heal naturally. Analysis of the provided sources reveals varying trends in the preference and frequency of these treatment approaches across different countries and time periods. Denmark has observed a notable decrease in the proportion of patients undergoing surgical treatment for acute Achilles tendon rupture between 1994 and 2013¹³. Similarly, Sweden has experienced a decline in surgical incidence rates for this injury from 2002 to 2021⁹. In North America, Ontario, Canada, reported a significant decrease in the annual rate of surgical repair for acute Achilles tendon ruptures between 2003 and 2013¹². Finland has also seen a reduction in the incidence of operative treatment for Achilles tendon ruptures from 1997 to 2019¹¹. In contrast, Japan has shown a significant increase in the annual proportion of surgical treatment for Achilles tendon ruptures between 2010 and 2017⁸. South Korea has also reported an increasing trend in the overall incidence of surgical treatment for these injuries¹⁴. Germany indicates a growing preference for surgical management of Achilles tendon ruptures⁶⁴. On the other hand, the United States did not exhibit a significant change in the trend of operative versus non-operative treatment between 2005 and 2011⁶⁵. These shifts in treatment preferences likely reflect the evolving understanding of the outcomes associated with surgical and non-surgical management, as well as patient and physician factors. While these trends in treatment do not directly influence the incidence of Achilles tendon ruptures, they are important to consider when interpreting epidemiological data, as they can affect the number of reported surgical procedures for the injury.

7. Regional Insights and Country-Specific Observations

The global analysis of Achilles tendon rupture incidence reveals several unique findings and trends that are specific to individual countries, highlighting the influence of local factors on the epidemiology of this injury. New Zealand presents a distinctive case with a high incidence of Achilles tendon rupture among women, primarily attributed to their widespread participation in netball. This sport-specific injury pattern also results in a younger average age of injury in New Zealand compared to typical reports from other regions¹⁶. Sweden has experienced a notable acceleration in the increase of Achilles tendon rupture incidence rates since 2017. This recent surge contrasts with the trends observed in other parts of Europe and Asia, suggesting that specific factors within Sweden's population or environment may be contributing to this accelerated rise¹⁰. Japan stands out with a relatively stable incidence of Achilles tendon rupture between 2010 and 2017. This finding is in contrast to the increasing trends reported in Scandinavian countries during similar timeframes, indicating potential differences in lifestyle, sports participation, or other risk factors between these regions⁸. In South Korea, socioeconomic factors appear to play a role, as a higher income level was associated with an increased incidence of Achilles tendon rupture⁶⁶. Additionally, the incidence of this injury in South Korea shows a seasonal pattern, with higher rates reported during the spring and summer months and the lowest incidence occurring in winter⁶⁶. This seasonal variation may be linked to changes in physical activity patterns throughout the year. These country-specific observations underscore the importance of considering local contexts when examining the epidemiology of Achilles tendon ruptures. Factors such as the popularity of particular sports, socioeconomic conditions, and even environmental influences can significantly shape the incidence and characteristics of this injury within different geographical regions.

8. Implications for Prevention and Risk Management

The synthesis of the identified causes and risk factors for Achilles tendon rupture provides a foundation for formulating evidence-based recommendations aimed at prevention and risk management. Several strategies can be implemented to potentially reduce the incidence of this injury. Engaging in proper warm-up routines and incorporating stretching exercises before participating in any physical activity is crucial for preparing the Achilles tendon and the surrounding muscles for the demands of exercise, thereby reducing the risk of sudden rupture³. Gradually increasing the intensity and duration of training programs allows the Achilles tendon to adapt to increasing loads over time, minimizing the risk of injury due to sudden overload⁴⁶. Incorporating regular calf-strengthening exercises into fitness routines can enhance the tendon's capacity to absorb force and withstand stress, thus lowering the likelihood of rupture⁵⁵. Wearing appropriate footwear that provides adequate cushioning and support, particularly in the heel area, is essential for minimizing stress on the Achilles tendon during physical activities⁵⁶. Engaging in cross-training activities and incorporating low-impact exercises into workout regimens can help to avoid overuse of the Achilles tendon and promote overall musculoskeletal health, reducing the risk of injury from repetitive strain²⁶. Individuals should also be aware of the potential risks associated with certain medications, such as fluoroquinolone antibiotics and corticosteroid injections, and should discuss alternative treatment options with their healthcare providers if possible, especially if they are at higher risk for tendon injuries³. Maintaining a healthy body weight can significantly reduce the overall strain on the Achilles tendon, thereby lowering the risk of rupture⁴³. Finally, it is crucial to listen to the body and take adequate rest when experiencing any pain or discomfort in the Achilles tendon area, as pushing through pain can exacerbate minor issues and potentially lead to a more severe injury like a rupture⁵⁶. By focusing on these modifiable risk factors and promoting healthy lifestyle choices and safe exercise practices, it may be possible to mitigate the increasing global trend of Achilles tendon ruptures. Targeted prevention programs could also be developed based on the incidence patterns observed in specific sports and demographic groups.

9. Conclusion

In summary, the analysis of global trends in Achilles tendon rupture incidence reveals a general increasing trend in many regions, particularly in Northern Europe and North America. Japan stands out with a stable incidence during the studied period, while significant variations are observed across different countries. The key factors identified as driving these changes include aging and increasingly active populations, greater participation in high-impact sports, the prevalence of pre-existing tendon degeneration, the use of certain medications known to weaken tendons, rising rates of obesity, and potentially socioeconomic factors that influence lifestyle and access to sports. While this report provides a valuable overview based on the available research, it is important to acknowledge the limitations inherent in the data. These limitations include varying study periods, inconsistencies in methodologies across different studies, a lack of comprehensive data for certain geographical regions, and the potential for reporting bias. These factors underscore the need for more standardized and comprehensive epidemiological studies conducted across a wider range of countries to enable more direct and reliable comparisons of incidence rates and trends. Future research should also focus on undertaking more in-depth investigations into the complex role of socioeconomic and occupational factors in Achilles tendon rupture, as well as performing longitudinal studies to assess the long-term impact of prevention strategies and treatment trends on incidence rates. Ultimately, a more complete understanding of the global epidemiology of this prevalent injury is essential for developing more effective prevention and management strategies to address this growing public health concern.