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CASE REPORT

Lower Limb Injuries in Regular Runners—An Asian Perspective

Ng Yau Hong * Teo Wei Wen Timothy** Chan Yiong Huak*** 

Lee Boon Leng Kevin****

*Resident, Department of Orthopaedic Surgery, National University Hospital, Singapore

**Resident, Department of Orthopaedic Surgery, National University Hospital, Singapore

***Head of Biostatistics Unit, Yong Loo Lin School of Medicine, National University Health System, Singapore

****Consultant Orthopaedic Surgeon and Medical Director, Centre for Joint and Cartilage Surgery, Singapore

Address for Correspondence

Ng Yau Hong 

5 Lower Kent Ridge Road, Singapore 119074

P hone:+65 67795555 

Fax: +65 67795678

E-mail:honggg_85@hotmail.com 
 

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Abstract:

Introduction: Long distance running is known to be associated with lower limb injuries, but risk predictors for these running injuries are controversial. Our retrospective case control study aims to determine the incidence of running injuries in the Asian population and the potential risk factors for these injuries. Materials and Methods: Lower limb injuries in five hundred and nine (509) Asian runners and triathletes from 24 local athletic clubs and associations were analyzed through an anonymous email questionnaire. Results: More than one-third (36.0%) of the 509 runners had lower limb injuries, of which 65.0% were attributed to the long-distance training. Although the majority of these were simple strains and sprains (64.0%), a significant proportion (8.7%) required surgical treatment. Female gender, uneven running surfaces and pure runners, as opposed to triathletes, were found to be positive risk predictors for lower limb running injuries (p<0.05). Conclusions: We recommend long-distance training on even surfaces and appropriately adjusted weekly mileage to reduce incidence of lower limb injuries in long-distance runners. More large-scale studies are needed to better evaluate the risk predictors for running-related injuries.

J.Orthopaedics 2012;9(2)e6

Keywords:

long-distance running; knee injuries; risk factors; Asian population; running surface; mileage



Introduction:

Endurance sports such as long-distance running and triathlons have become increasingly popular in Asia and this is in no small part due to an increasing health-consciousness of a more well-educated public. The aerobic sport has a positive effect on cardiovascular health, and helps combat obesity.1-4 However it is also a well-documented fact that long-distance running comes with its own set of associated morbidities, particularly lower extremity injuries. Several studies exploring the incidence rates of such running injuries2,3,5,6 and their contributory risk factors2,5 have been done in a variety of settings, but results have been inconclusive and controversial. A systematic review of numerous studies done in various parts of the Western world like the Netherlands, Germany and Sweden by van Gent et al7 revealed a large discrepancy in incidence rates of running injuries.

Training distance has been found to be a risk factor for running injuries in many studies,7-10 but there are also authors who disagree.11 Asian populations are generally under-represented in many existing studies on this subject. It is a known fact Asian and Caucasian populations have significant differences in lower limb anatomy and biomechanics.12-14 It is also shown that there are social differences in the patients' attitudes towards seeking medical care and consultations of traditional medical practitioners.15             The present study aims to determine the incidence of lower extremity injuries in runners and triathletes in an Asian population, and through a retrospective analysis of the runners’ profiles, the potential risk factors for these injuries.

Methods:

The study was conducted in Singapore, which has a predominant Asian population, with 74.2% Chinese, 13.4% Malays, 9.2% Indians and 3.2% Eurasians and other minority racial groups. It was designed as an anonymous email questionnaire-based retrospective study which was conducted after receiving Institutional Review Board (IRB) approval. Questionnaires were sent to members of 24 local athletic clubs and associations, including major national running associations and recreational clubs. Runners included in the study were individuals who ran on a regular basis, defined as a minimum of 5km per week for 5 years or more.

A distance of 5 km of walking or running per week, is seen throughout literature as the minimum required for a significant reduction in the risk of coronary artery disease.16 Our inclusion criteria also ensured that regular recreational runners were not excluded from the study. The study subjects ranged from amateur to professional runners. A total of 875 questionnaires were sent out to the various clubs and associations. Five hundred and sixty questionnaires were returned, of which 41 were rejected because the respondents did not meet the inclusion criteria. 10 questionnaires were incomplete and voided as well.          

   The questionnaire surveyed the runners on their running patterns, in terms of variables like average weekly mileage, frequency of training and types of running surface, as well as the injuries they had sustained through running. Running injuries were defined as pain or bodily dysfunction causing inability to continue with the sport at the usual intensity, occurring during or shortly after a run.             Respondents were subsequently stratified according to their demographics like age, gender and race, and statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS version 16.0) by our biostatistician collaborator.

 

Results      

       Five hundred and nine runners were included in the study. The demographic data of the runners are presented in Table 1. The respondents were a highly-educated group, with undergraduates, graduates and postgraduates making up more than half of the study population (68.8%). Majority of the runners were aged between 15-35 years old (71.5%). The majority (80.4%) of these runners were male and were predominantly Chinese (84.1%), which corresponds with the racial distribution in Singapore. Of these runners, 5.1% were pure triathletes who did long-distance running purely as part of their training for triathlons, 83.5% were pure runners who never did triathlons and 11.4% did both running and triathlons. A large proportion of these athletes (76.8%) also did sports other than long-distance or triathlon training, such as soccer, racquet games and water sports. More than one-third (36.0%) of the 509 runners had lower limb injuries, of which 65.0% were attributed to the long-distance training. Most of these injuries were simple strains and sprains (64.0%); other major injuries include meniscal injuries (10.9%) and cruciate ligament injuries (10.4%).

A significant number of these injuries (8.7%) required surgical treatment. The distribution of injury types is illustrated in Table 2. These injuries affected the athletes both at the time of injury and at the time of the survey. More than half of these athletes (57.3%) could not continue training with the same intensity at the time of injury and up to 57.9% of the athletes were still bothered by their injuries at the time of the survey, to various extents. Table 3 illustrates the effects of the injuries on the athletes in greater detail. To determine possible risk factors for running injuries, running patterns of these athletes were analyzed. No statistically significant association was found between incidence of running injuries and the number of years of training (p=0.210). Overall, frequency of running also appeared to have no bearing on the incidence of running injuries (p=0.121).

There was however a statistically significant association between the average weekly mileage and running injuries (p=0.015). Runners who ran 11 to 30km per week (p=0.007, OR=1.7, 95% CI 1.2-2.5) as well as runners who ran more than 30km per week (p=0.050, OR=1.8, 95% CI 1.01-3.2) were more likely to sustain running. The warm-up time did not appear to have an effect on injury rate (p=0.469). Upon a multivariate regression analysis (see Table 1), the following factors were found to be significantly linked to running injuries. The female gender appeared to have an increased risk of sustaining running injuries (p=0.022, OR=1.8, 95% CI 1.1-3.1), compared to males. Runners who had previously trained on uneven running surfaces, like trails and park routes, were also at an increased risk of sustaining running injuries as compared to those who only ran on level running surfaces, like treadmills, roads and stadium tracks (p=0.016, OR=1.7, 95% CI 1.1-2.5). Pure runners also had a statistically significant increased risk of sustaining running injuries as compared to pure triathletes (p=0.041, OR=3.0, 95% CI 1.1-8.8). Subjects who did both running and triathlon showed a trend of increased risk too (p=0.068, OR=3.0, 95% CI 0.92-9.6).

 

 

Discussion:

Endurance sports like long-distance running and triathlons are becoming increasingly popular worldwide. In Singapore, jogging has consistently been the single most popular sport and participation rate has increased steadily over the years from 13.3% in 2001 to 21.1% in 2005.17 Participation rates for mass events like the Singapore Marathon and Singapore International Triathlon have also seen exponential increases over the recent few years, with a record of 40,000 runners participating in the former event in 2007.                    

   Several biomechanical research studies have shown deformation and degenerative changes in articular cartilage after repetitive impulsive forces and mechanical loading.18-21 Load-dependent volume changes of knee meniscal cartilage,22 and relationship between training levels of long-distance runners and chronic knee lesions23 have also been reported in MRI studies. As cartilaginous injuries tend to recover poorly, premature osteoarthritis may result. This coupled with the increasing number of long-distance runners worldwide may result in an epidemic of osteoarthritis in the years to come.

            Based on the results of our study, we found that the positive predictors for increased risk of running injuries to be female gender, uneven running surfaces and pure runners (as compared to pure triathletes). Our study showed that females were significantly more likely to sustain running-related lower limb injuries than males. This finding correlates with that of several other published studies, particularly with regards to anterior cruciate ligament injuries and anterior knee pain syndrome from running.7, 24-27 This predisposition of females to lower limb injuries from running has been attributed to a combination of biomechanical, neuromuscular and hormonal factors.

There was however an MRI study by Schueller-Weidekamm et al23 which found no significant difference in chronic knee lesions on MRI between male and female runners. This disparity between radiological and clinical findings possibly reflects an under-diagnosis and hence under-treatment of running-related lower limb injuries in the male gender, as a result of under-reporting of symptoms in this group of athletes. We also found that the incidence of knee injuries was higher in runners who had previously trained on uneven running surfaces, like park routes and trails, as compared to those who only trained on even running surfaces like treadmills and stadium tracks. This is probably a result of cumulative subclinical trauma to the joint cartilage from increased joint reaction forces and also an increased likelihood of sprains and strains.            

The lower incidence rate of lower limb injuries in triathletes compared to pure runners could be due to the higher weekly mileage clocked by the pure runners, with consequent increased microtrauma and stress to the lower limb ligaments and joints.      

       To prevent running-related injuries, we advise long-distance runners, particular the non-competitive runners, to train on even surfaces as much as possible and weekly mileage should also be adjusted according to the level of fitness of the individual. More large-scale studies need to be done to develop proper guidelines on the optimal training regime for long-distance running. We are now embarking on a study looking at injuries in female runners in particular, as well as marathoners and ultra-marathoners with longer cumulative training mileage. 

TABLE 1

Runners' profile

 

 

 

 

 

 

 

 

Unadjusted (univariate analysis)

Adjusted (multivariate analysis)

 

Running injuries(%)

OR(95% CI)

p-value

OR(95% CI)

p-value

Age (years)

 

 

 

 

 

15-25 (n=182)

31.3

1.0

 

1.0

 

26-35 (n= 182)

40.1

1.5(0.95-2.3)

0.081

1.4(0.8-2.5)

0.212

36-45 (n=97)

37.1

1.3(0.8-2.2)

0.329

1.5(0.8-2.8)

0.217

46-55 (n= 41)

39.0

1.4(0.7-2.8)

0.343

1.6(0.7-3.6)

0.300

56-65 (n=7)

14.3

0.4(0.04-3.1)

0.357

0.5(0.05-4.4)

0.504

Gender

 

 

 

 

 

Male (n=409)

47.0

1.0

 

1.0

 

Female (n=100)

33.3

1.8(1.1-2.8)

0.011

1.8(1.1-3.1)

0.022

Race

 

 

 

 

 

Chinese (n=428)

37.1

1.0

 

1.0

 

Malay (n=16) 

43.8

1.3(0.5-3.6)

0.593

1.0(0.3-3.1)

0.953

Indian (n=27) 

29.6

0.7(0.3-1.7)

0.434

0.5(0.2-1.3)

0.151

Others (n=38)

23.7

0.5(0.2-1.1)

0.102

0.5(0.2-1.2)

0.128

Frequency of running

 

 

 

(times per week)

 

 

 

 

1-2 (n=256)

32.0

1.0

 

1.0

 

3-4 (n=217)

41.0

1.5(1.02-2.2)

0.043

1.3(0.8-2.0)

0.359

5 or more (n=36)

33.3

1.1(0.5-2.2)

0.876

1.0(0.4-2.4)

0.983

Average mileage 

 

 

 

 

(kilometres per week)

 

 

 

 5-10 (n=244)

29.5

1.0

 

1.0

 

11-30 (n=204)

41.7

1.7(1.2-2.5)

0.007

1.5(0.9-2.4)

0.120

>30 (n=61)

42.6

1.8(1.01-3.2)

0.050

1.5(0.7-3.3)

0.273

Number of years of training

 

 

 

<2 (n=199)

30.7

1.0

 

1.0

 

2-5 (n=158)

39.2

1.5(0.9-2.3)

0.091

1.2(0.7-2.0)

0.451

5-10 (n=63)

42.9

1.7(0.9-3.0)

0.075

1.3(0.7-2.5)

0.452

>10 (n=89)

37.1

1.3(0.8-2.3)

0.283

1.1(0.6-2.1)

0.776

Type of running surface

 

 

 

Only on even surface (n=194)

27.8

1.0

 

1.0

 

Uneven surface (n=315)

41.0

1.8(1.2-2.6)

0.003

1.7(1.1-2.5)

0.016

Warm-up time

 

 

 

 

 

No (n=74)

32.4

1.0

 

1.0

 

<10min (n=374)

35.3

1.1(0.7-1.9)

0.637

1.2(0.6-2.0)

0.633

≥10min (n=59)

42.4

1.5(0.8-3.1)

0.239

1.5(0.7-3.2)

0.313

Activity type

 

 

 

 

 

Pure triathletes (n=26)

19.2

1.0

 

1.0

 

Pure runners (n=425)

36.0

2.4(0.87-6.4)

0.090

3.0(1.1-8.8)

0.041

Both (n=58)

43.1

3.2(1.1-9.6)

0.040

3.0(0.92-9.6)

0.068

 

TABLE 2

 

Types of running injuries (some patients had >1 injury)

 

 

 

 

 

Frequency

 

 

Strain/sprain

117(64.0%)

 

Meniscal injury

20(10.9%)

 

 

Cruciate ligament injury

19(10.4%)

 

 

Others

 

 

 

Chondromalacia patellae

10(5.5%)

 

 

Metatarsalgia

8(4.4%)

 

 

Knee dislocation

1(0.6%)

 

 

Stress fractures

3(1.6%)

 

 

Tendinitis

8(4.4%)

 

 

Plantar fasciitis

11(6.0%)

 

 

Low back pain

10(5.5%)

 

 

TABLE 3

 

 

Effect of injury

 

 

 

 

 

 

 

Frequency

 

 

 

 

At time of injury

 

 

 

 

Totally lay off

20(10.9%)

 

 

 

 

Cut down mileage

85(46.4%)

 

 

 

 

Continue at same intensity

78(42.6%)

 

 

 

 

Currently

 

 

 

 

 

(At time of study)

 

 

 

 

No longer bothered by injury

77(42.1%)

 

 

 

 

Gave up running totally

4(2.2%)

 

 

 

 

Cut down mileage but not taking medication

57(31.1%)

 

 

 

 

Taking medication but not cutting down mileage

19(10.4%)

 

 

 

 

Not cutting down mileage and not taking medication

26(14.2%)

 

 

 

 

 

 

 

 

 

 

Surgery needed?

 

 

 

 

Yes

16(8.7%)

 

 

 

 

No

167(91.3%)

 

 

 


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This is a peer reviewed paper 

Please cite as : Ng Yau Hong ,Lower Limb Injuries in Regular Runners—An Asian Perspective.

J.Orthopaedics 2012;9(2)e6

URL: http://www.jortho.org/2012/9/2/e6

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