Increased Incidence of Hamstring Injuries in the United States From 2015 to 2024 and Projected Growth Through 2030

Purpose

To evaluate the epidemiology of hamstring tendon injuries in the United States from 2015 to 2024 and to project incidence trends through 2030.

Methods

Patients diagnosed with hamstring strains between 2015 and 2024 were identified using International Classification of Diseases, 10th Revision code S76.31. Data were collected using the TriNetX US Collaborative Research Platform, which includes over 120 million deidentified patient records. Incidence proportion was calculated annually. Demographic substratification by age and sex was performed, and linear regression was used to project incidence through 2030.

Results

A total of 118,197 patients with hamstring injuries were identified, with a mean age of 48.7 years; 49% were female. In 2024, hamstring injury incidence was 42.79 per 100,000 (95% confidence interval, 42.01-43.98), a significant increase from 11.61 per 100,000 (95% confidence interval, 11.28-11.94) in 2015 ( P <.001). A bimodal distribution was noted, with the highest total number of injuries in adults aged 60 to 64 years and the highest incidence proportion in those aged 15 to 19 years. Under age 35 years, males had higher injury rates, while over age 35 years, females had higher rates. Projections estimate that incidence will rise to 56.2 per 100,000 by 2030 ( R ² = 0.83), reflecting a 6.7% average annual increase through 2030.

Conclusions

There is a rising burden of hamstring injuries in the general population, with the highest incidence among older adults and young people. Projections based on current trends estimate that the annual incidence of these injuries will continue to rise.

Level of Evidence

Level IV, descriptive epidemiologic study.

Hamstring strains are common muscle injuries, accounting for 12% to 29% of injuries in athletes, with recurrence rates exceeding 30%. ^,^,^,^, The hamstring muscle includes the semimembranosus, semitendinosus, and biceps femoris, which comprises both long and short heads. Injury typically occurs during the terminal swing phase of the gait cycle while sprinting, often presenting with an acute onset of posterior thigh pain.

Diagnosis is primarily clinical, supported by findings including ecchymosis, localized tenderness, swelling, a palpable defect, and weakness with resisted hip extension or knee flexion. ^, Radiographs are useful for detecting avulsion injuries, while magnetic resonance imaging is preferred for evaluating the extent and location of soft tissue injury. ^,^, Management depends on severity: mild to moderate strains are typically treated nonoperatively with rest, ice, physical therapy, and a gradual return to activity, whereas high-grade injuries may benefit from surgical intervention to restore function and minimize long-term deficits. ^,^,^,

Contemporary literature on hamstring tendon injuries has predominantly focused on athletic and physically active populations, with studies showing hamstring tendon injuries constituting 10% to 24% of all injuries in field-based team sports. ^,^,^,^, Furthermore, studies among athletic populations have found a rising annual incidence as these injuries become more recognized. Specifically, in men’s professional football, hamstring injury rates have increased by 6.7% annually from 2001 to 2022. ^, However, the broader epidemiology of hamstring injuries among recreational and nonathletic populations remains poorly defined. These patterns highlight the importance of examining epidemiologic trends in the broader US population, beyond competitive athletes. The purpose of this study was to evaluate the epidemiology of hamstring tendon injuries in the United States from 2015 to 2024 and to project incidence trends through 2030. We hypothesized that our findings would show a continued rise in the annual incidence of hamstring injuries, with projections indicating further increases through 2030.

Methods

Study Design

The TriNetX US Collaborative Research Platform was used to conduct a retrospective, multicenter study examining trends in hamstring injuries in the United States. The platform has access to over 70 health care organizations and 121 million electronic patient records, comprising almost one-third of the US population. The data are entirely deidentified in accordance with §164.514(b)(1) of the Health Insurance Portability and Accountability Act Privacy Rule, using expert-certified methods such as obfuscation and minimum thresholds, guaranteeing that each query includes at least 10 individuals. As a result, it does not qualify as Protected Health Information and is not subject to Health Insurance Portability and Accountability Act or institutional review board regulations. All data in the platform are accessed through the use of insurance billing codes, including the International Classification of Diseases, 10th Revision ( ICD-10 ) and Current Procedural Terminology codes.

Cohort Creation

All patients with hamstring tendon injuries in the research platform were identified using the ICD-10 code S76.31. Only patients in the United States were considered for analysis, and the study period was restricted from 2015 to 2024. Patients without ICD-10 code S76.31 and those outside the United States were excluded from analysis. Patients were substratified by demographic characteristics, including sex and age.

Outcomes Evaluated

The primary epidemiologic outcome evaluated was incidence proportion (IP), which was defined as the number of new hamstring strain cases diagnosed in a given year divided by the total population at risk that year. We define the total population at risk for each year as the number of unique individuals who had at least 1 health care encounter recorded in the database during that year. Diagnoses prior to 2015 were excluded from the analysis due to a substantial reduction in the number of health care organizations contributing data to the TriNetX platform before that year. General information on the cohort was also collected, including demographic information, comorbidities, and geographic distribution. A linear regression was performed to project the incidence of hamstring strains to 2030. This time frame was selected to maintain predictive accuracy and avoid excessive uncertainty associated with longer-term extrapolations. Model fit was assessed using R ².

Statistical Analysis

The incidence proportion was calculated using the epidemiologic tools within the TriNetX platform. A Poisson distribution was assumed to generate a 95% confidence interval (CI) for the incidence proportion values. Rates between years and demographic categories were compared using a χ ² test. A P value of less than.05 was considered significant.

Results

Cohort Characteristics

From 2015 to 2024, a total of 118,197 patients were diagnosed with a hamstring strain ( Table 1 ). The mean age of the cohort was 48.7 ± 21.2 years. Females accounted for approximately 49% of the cohort, while males comprised 46%. Most patients were White (70%), followed by African American patients (12%). Essential hypertension was the most common comorbidity, affecting one-third of patients. Geographically, most diagnoses occurred in the Northeast (33%), closely followed by the South (30%).

Table 1

Hamstring Strain Cohort Characteristics (n = 118,197)

Characteristic	Value
Age, y	48.7 ± 21.2
Sex
Male	51,182 (46)
Female	54,825 (49)
Unknown	5,600 (5)
Race
White	77,827 (70)
Unknown	12,288 (11)
Black or African American	13,912 (12)
Asian	2,590 (2)
Other	3,883 (3)
Body mass index	28.5 ± 7.12
Comorbidities
Nicotine dependence	8,302 (7)
Diabetes mellitus	13,242 (12)
Essential (primary) hypertension	34,559 (31)
Overweight, obesity, and other hyperalimentation	21,602 (19)
Chronic lower respiratory disease	20,999 (19)
Acute kidney failure and chronic kidney disease	7,132 (6)
Iron-deficiency anemia	5,344 (5)
Metabolic syndrome	327 (<1)
Geographic distribution
Northeast	39,835 (33)
Midwest	27,729 (23)
South	35,126 (30)
West	14,992 (13)
Unknown	1,388 (1)

NOTE. Values are presented as n (%) or mean ± standard deviation.

Overall Trends in Hamstring Injuries

In 2024, the IP was 42.8 (95% CI, 42.0-44.0) cases per 100,000 patients, which was significantly higher than in 2015, when the IP was 11.6 (95% CI, 11.3-11.9) cases per 100,000 patients ( P <.001). The IP observed a sharp increase from 2015 to 2016 (92.4%), followed by a gradual increase from 2016 to 2019. A marked decline occurred in 2020 (24.8% decrease), but values rebounded in 2021 to levels similar to 2019 and continued to rise through 2024 ( Fig 1 ).

Image, AltText currently not available — Fig 1

Hamstring Injuries by Sex and Age

From 2015 to 2024, males had a significantly higher IP of hamstring injuries than females ( P <.01). In 2024, males had an IP of 49.9 (95% CI, 48.8-51.1) cases per 100,000 patients, and females had an IP of 37.6 (95% CI, 36.6-38.6) cases per 100,000 patients ( Fig 2 ).

When stratified by age, IP was significantly increased among all age groups when comparing values between 2015 and 2024 ( P <.01). Regarding IP, the 15- to 19-year age group experienced the highest IP, with 78.8 (95% CI, 74.7-82.9) cases per 100,000 patients, followed by the 65- to 69-year age group, which had an IP of 57.8 (95% CI, 54.8-60.8) cases per 100,000 patients ( Fig 3 ).

An analysis of male and female rates stratified by age from 2015 to 2024 observed that female patients between the ages of 60 and 64 years experienced the highest total number of hamstring injury cases (208.8 cases per 100,000 patients; 95% CI, 203.4-214.2), followed by males between the ages of 10 and 14 years (198.6 cases per 100,000 patients; 95% CI, 193.1-204.0). In contrast, among females, patients between the ages of 20 and 24 years experienced the lowest number of hamstring strains (49.6 cases per 100,000 patients; 95% CI, 47.3-51.9), while males older than 85 years experienced the lowest rate of hamstring strains (55.6 cases per 100,000 patients; 95% CI, 48.3-63.2) ( Fig 4 ).