Original article
Br J Sports Med 2011;45:1026–1028. doi:10.1136/bjsports-2011-0903421026
1
Sports Medicine Department,
The Hague Medical Centre,
Leidschendam,
The Netherlands
2
Department of Orthopaedics,
Erasmus Medical Centre,
Rotterdam, The Netherlands
3
Department of Orthopaedics,
Leiden University Medical
Centre, Leiden,
The Netherlands
4
Department of General
Practice, Erasmus University
Medical Centre, Rotterdam,
The Netherlands
Correspondence to
S de Jonge, Orthopaedic
Research Laboratory, Erasmus
MC, PO Box 2040, 3000 CA
Rotterdam, The Netherlands;
s.dejonge@erasmusmc.nl
Accepted 3 August 2011
Incidence of midportion Achilles tendinopathy in
the general population
S de Jonge,
1,2
C van den Berg,
1
R J de Vos,
1
H J L van der Heide,
3
A Weir,
1
J A N Verhaar,
2
S M A Bierma-Zeinstra,
2,4
J L Tol
1
ABSTRACT
Background Achilles tendon disorders, like Achilles
tendinopathy, are very common among athletes. In
the general population, however, knowledge about the
incidence of Achilles tendinopathy is lacking.
Design Cross-sectional study.
Methods In a cohort of 57.725 persons registered in
primary care, the number of patients visiting the general
practitioner (GP) with diagnosis of mid-portion Achilles
tendon problems was counted using computerised
registration networks of GPs in 2009. Subsequently,
the authors assessed associations of these rates with
demographic characteristics.
Results The incidence rate of Achilles tendinopathy is
1.85 per 1,000 Dutch GP registered patients. In the adult
population (21–60 years), the incidence rate is 2.35 per
1,000. In 35% of the cases, a relationship with sports
activity was recorded.
Conclusion This is the fi rst report on incidence rates
of mid-portion Achilles tendinopathy in general practice.
With an incidence of 1.85 per 1,000 registered persons,
Achilles tendinopathy is frequently seen by GPs. The
actual incidence might even be higher due to study
limitations. More research on the frequency of this injury
is required.
INTRODUCTION
Achilles tendon problems frequently occur in ath-
letes and are supposed to be common as well in
the general population. The frequency of Achilles
tendinopathy in athletes has been reported in
several studies. Elite long-distance runners have
a lifetime risk of 52%, and the lifetime incidence
of 416 participants of Finnish conscription was
5.9%.
1
Others reported annual incidence rates of
Achilles tendon disorders of 7% and 9%, respec-
tively, in top-level runners.
2 3
Among the military
population, an incidence of 2.98 per 1,000 person
years was found.
4
A cohort study of 725 male
marathon runners reported an incidence of 7.4%
in the month before the Rotterdam marathon.
5
While these frequency rates were recorded in
the sporting population, Achilles tendinopathy
is not always associated with excessive physical
activity; it is also seen in patients who do not par-
ticipate in sports.
6–8
To our knowledge, there are
no studies on the incidence of Achilles tendinopa-
thy in the general population. Incidence rates are
useful for studying trends in occurrence of dis-
eases, future intervention studies, and for burden
of disease estimates.
To obtain this incidence rate, a cross-sectional
study within the Dutch general practice setting
was performed. In the Netherlands, every non-in-
stitutionalised inhabitant is registered with a gen-
eral practitioner. In case of a health problem, the
general practice is intended to be a gatekeeper to
specialist care. The primary aim of this study was
to ascertain the frequency of mid-portion Achilles
tendinopathy seen in the general practitioner (GP)
setting.
METHODS
In this cross-sectional study, data were obtained
from computerised registration systems of Dutch
GPs. General practices were approached for par-
ticipation by mail and telephone. After permis-
sion, the researcher visited the practices.
During this visit, all electronic patient fi les
for consultations in 2009 were systematically
searched under supervision of the GP. GPs in the
Netherlands use International Classifi cation of
Primary Care (ICPC)
9
codes to register the reason
for the visit. These codes include disease-specifi c
codes as well as complaint specifi c codes. There
is, however, no specifi c code for Achilles tendi-
nopathy. Another sensitive way of searching for
certain diagnosis is to use diagnosis specifi c words
in the free text of the records. We searched for the
term achil to fi nd as many records describing the
diagnosis of Achilles tendinopathy (eg, terms as
Achillodynia could also be found). Medical fi les of
the found records were read by a single researcher
(CvdB) to assess whether they met the inclusion
criteria. For the diagnosis of Achilles tendinopa-
thy, a description of pain in the Achilles tendon
above the insertion was required. Lack of this
description resulted in exclusion. When the fi rst
contact with the GP for complaints was in the year
2009 without a previous visit in 2008, the patient
was scored as an incident case. In addition, age,
gender, date of presentation and sports activity
(related to complaints) were recorded if these had
been recorded in the medical record. The medi-
cal record was also screened for diabetes mellitus
(DM) type 1 and 2.
Statistical analysis was performed using SPSS
(version 17). Incidence rates were calculated sepa-
rately for age group and sex.
RESULTS
Between February 2011 and April 2011, 128 gen-
eral practices were approached. Fourteen practi-
tioners did not answer repeated phone calls and 94
GPs refused to participate. Twenty GPs at differ-
ent geographic locations responded positively to
the invitation and were visited by the researcher.
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Original article
Br J Sports Med 2011;45:1026–1028. doi:10.1136/bjsports-2011-090342 1027
The 20 participating practices contained 57.725 registered per-
sons, with an average of 2,886 persons in each practice (range
1,757–6,486).
The research strategy “Achil” in the free text resulted in
277 cases in 2009. After screening the medical fi les, 116 cases
of mid-portion Achilles tendinopathy could be recorded.
Frequently reported other Achilles tendon disorders were
insertional disorder, lash and bursitis. The prevalence rate of
Achilles tendinopathy is 2.01 per 1,000 registered patients.
Of these 116 prevalent cases, 9 patients had visited the gen-
eral practitioner in 2008 for the same reason, resulting in 107
incident cases in 2009. The incidence rate for mid-portion
Achilles tendinopathy is 1.85 per 1,000 registered patients.
The 107 incident cases contained 56 females (52.3%) and 51
males (47.7%). Age- and sex-specifi c incidence rates are given
in table 1. The overall incidence rate in the adult population
between 21 and 60 years is 2.35 per 1,000. The mean age at
time of presentation within the cases was 43.4 years (range
7–85 years). Mid-portion Achilles tendinopathy equally affects
women and men.
Mean duration of symptoms at presentation (reported in 39
cases) was 11.3 weeks (range 1–52). In 37 cases (34.6%), a rela-
tionship with sports activity was recorded. Ten patients (9.3%)
were known to have DM—two patients with type 1 DM and
eight patients with type 2 DM. Table 2 shows the patient char-
acteristics of the case group compared with the study popula-
tion and the Dutch population.
DISCUSSION
This is the fi rst study presenting incidence rates of Achilles
tendinopathy in the general practice. The overall incidence rate
is 1.85 per 1,000 registered persons per year, and for the adult
population it is 2.35. There are no other studies on the inci-
dence rates of Achilles tendinopathy in the general population
to compare these results with. The prevalence rate was higher
than that for another tendinopathy like lateral epicondylitis of
1.3% (men) and 1.1% (women) in 9,696 persons registered at
two general practitioners.
10
The incidence rates in our study are lower than the incidence
of 2.98 found in the military population
4
and than the annual
incidence 7% and 9% in top-level runners.
2 3
While it seems plausible that the incidence rate of Achilles
tendon injuries is higher in athletes than within a more general
population, only in 35% of the cases in our study was a relation-
ship with sports activity described. Intrinsic risk factors such
as body weight and insulin resistance might also play a role.
11
Although we could not assess information on body weight,
the diagnosis of DM was available from the medical records.
DM seemed more prevalent among the incident cases com-
pared with the general Dutch population (table 2). However,
more research is needed to draw any conclusions on a caus-
ative association The minor difference between the incidence
and prevalence rate suggests that most patients only visit their
GP once with their Achilles tendon problems. This might be
because of a short duration of symptoms or that the patients
go to a physiotherapist or sports physician afterwards.
This cross-sectional study has some limitations, due to
which the actual incidence of Achilles tendinopathy in the
general population is probably higher than observed in this
study.
Firstly, not every person with a certain complaint will visit a
healthcare professional. In a cross-sectional population-based
study, Picavet et al reported that approximately 50% of the
patients with musculoskeletal complaints visited a healthcare
professional.
12
However, those with severe or persistent com-
plaints will probably seek healthcare.
Second, while most patients in the Dutch healthcare system
will visit their GP before being referred to a therapist or special-
ist, since 2006 patients can visit a physiotherapist or sports phy-
sician without referral by a GP. It would be interesting to know
the incidence rates of Achilles tendinopathy within the patient
population of the Dutch physiotherapists and sports physicians
Table 1 Age and sex specifi c incidence rates for Achilles tendinopathy in 20 general practices
Age at time of diagnosis
< 20 years 21–40 years 41–60 years > 60 years Total
n Persons IR n Persons IR n Persons IR n Persons IR n Persons IR
Male 7 6371 1.1 13 7289 1.8 24 8459 2.8 7 5642 1.2 51 27761 1.8
Female 6 6342 0.9 21 7584 2.8 18 8996 2.0 11 7042 1.6 56 29964 1.9
Total 13 12713 1.0 34 14873 2.3 42 17455 2.4 18 12684 1.4 107 57725 1.9
n = number of persons with Achilles tendinopathy; Persons = number of registered persons; IR, incidence rate = number cases per 1000 registered persons.
Table 2 Patient characteristics in the cases with Achilles tendinopathy, in the total study population,
and in the Dutch population (as recorded by CBS, Statistics Netherlands http://www.cbs.nl 2009)
Patients with Achilles
tendinopathy (95% CI) n=207
Study population n=57.725
Dutch population in year 2009
n=16.485.787
Gender
Male 47.7% (95% CI, 38.0 to 57.3) 48.1% 49.5%
Female 52.3% (95% CI, 42.7 to 62.0) 51.9% 50.5%
Diabetes mellitus 9.3% (95% CI, 3.7 to 15.0) 4.1%
Type 1 1.8% (95% CI, 0 to 4.5) 0.8%
Type 2 7.5% (95% CI, 2.4 to 12.5) 3.3%
Age groups
<20 years 12.1% (95% CI, 5.9 to 18.4) 22.0% 23.9%
21–40 years 31.8% (95% CI, 22.8 to 40.7) 25.8% 25.7%
41–60 years 39.3% (95% CI, 29.8 to 48.7) 30.2% 35.5%
>60 years 16.8% (95% CI, 9.6 to 24.0) 22.0% 15.0%
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Original article
Br J Sports Med 2011;45:1026–1028. doi:10.1136/bjsports-2011-0903421028
as well, but since the denominators of these populations are
unknown, no exact incidence rates could be obtained.
Finally, because there is no specifi c registration code (ICPC)
available for Achilles tendinopathy, GPs register this injury
using other or more general codes. The search strategy “Achil”
is considered to be highly sensitive for Achilles tendon prob-
lems; however, there is a possibility of missing some cases.
Furthermore, the 13 patients less than 20 years old might have
a growth-related disorder rather than mid-portion Achilles
tendinopathy.
In concordance with other studies,
4 13
mo st c as es w ere enco un -
tered in the middle-aged population (age group 41–60 years). It
is unclear why Achilles tendinopathy is more frequent within
this age group. A possible explanation might be a higher inci-
dence of degenerative tendons, susceptible to overuse, in the
elderly.
CONCLUSION
In conclusion, this is the fi rst study to report an incidence rate
of Achilles tendinopathy in the general population. With an
incidence of 1.85 per 1,000 registered patients, and of 2.35 in
the adult population, more research on pathophysiology and
therapy is warranted.
Acknowledgements The authors would like to thank Marienke van Middelkoop,
PhD (Department of General Practice, Erasmus University Medical Centre,
Rotterdam, the Netherlands), for her contribution to the study design. The authors
thank the general practitioners for their participation in the study.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.
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