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Recurrence of Achilles tendon injuries in elite male football players is more common after early return to play: An 11-year follow-up of the UEFA Champions League injury study

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Background There is limited information about Achilles tendon disorders in professional football. Aims To investigate the incidence, injury circumstances, lay-off times and reinjury rates of Achilles tendon disorders in male professional football. Methods A total of 27 clubs from 10 countries and 1743 players have been followed prospectively during 11 seasons between 2001 and 2012. The team medical staff recorded individual player exposure and time-loss injuries. Results A total of 203 (2.5% of all injuries) Achilles tendon disorders were registered. A majority (96%) of the disorders were tendinopathies, and nine were partial or total ruptures. A higher injury rate was found during the preseason compared with the competitive season, 0.25 vs 0.18/1000 h (rate ratio (RR) 1.4, 95% CI 1.1 to 2.0; p=0.027). The mean lay-off time for Achilles tendinopathies was 23±37 (median=10, Q1=4 and Q3=24) days, while a rupture of the Achilles tendon, on average, caused 161±65 (median=169, Q1=110 and Q3=189) days of absence. Players with Achilles tendon disorders were significantly older than the rest of the cohort, with a mean age of 27.2±4 years vs 25.6±4.6 years (p<0.001). 27% of all Achilles tendinopathies were reinjuries. A higher reinjury risk was found after short recovery periods (31%) compared with longer recovery periods (13%) (RR 2.4, 95% CI 2.1 to 2.8; p<0.001). Conclusions Achilles tendon disorders account for 3.8% of the total lay-off time and are more common in older players. Recurrence is common after Achilles tendinopathies and the reinjury risk is higher after short recovery periods.
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Recurrence of Achilles tendon injuries in elite male
football players is more common after early return
to play: an 11-year follow-up of the UEFA
Champions League injury study
Mariann Gajhede-Knudsen,
1,2
Jan Ekstrand,
1,2,3
Henrik Magnusson,
2,4
Nicola Maffulli
5,6
1
Division of Community
Medicine, Department of
Medical and Health Sciences,
Linköping University,
Linköping, Sweden
2
Football Research Group,
Linköping University,
Linköping, Sweden
3
UEFA Medical Committee,
Nyon, Switzerland
4
Division of Physiotherapy,
Department of Medical and
Health Sciences, Linköping
University, Linköping, Sweden
5
Department of
Musculoskeletal Disorders,
University of Salerno, School of
Medicine and Surgery, Salerno,
Italy
6
Queen Mary University of
London, Centre for Sports and
Exercise Medicine, London, UK
Correspondence to
Professor Jan Ekstrand,
Solstigen 3, S-589 43,
Linköping, Sweden;
jan.ekstrand@telia.com
Received 2 February 2013
Revised 14 April 2013
Accepted 12 May 2013
Published Online First
14 June 2013
To cite: Gajhede-
Knudsen M, Ekstrand J,
Magnusson H, et al. Br J
Sports Med 2013;47:
763768.
ABSTRACT
Background There is limited information about
Achilles tendon disorders in professional football.
Aims To investigate the incidence, injury circumstances,
lay-off times and reinjury rates of Achilles tendon
disorders in male professional football.
Methods A total of 27 clubs from 10 countries and
1743 players have been followed prospectively during 11
seasons between 2001 and 2012. The team medical
staff recorded individual player exposure and time-loss
injuries.
Results A total of 203 (2.5% of all injuries) Achilles
tendon disorders were registered. A majority (96%) of
the disorder s were tendinopathies, and nine were partial
or total ruptures. A higher injury rate was found
during the preseason compared with the competitive
season, 0.25 vs 0.18/1000 h (rate ratio (RR) 1.4, 95%
CI 1.1 to 2.0; p=0.027). The mean lay-off time for
Achilles tendinopathies was 23±37 (median=10, Q
1
=4
and Q
3
=24) days, while a rupture of the Achilles
tendon, on average, caused 161±65 (median=169,
Q
1
=110 and Q
3
=189) days of absence. Players with
Achilles tendon disorders were signicantly older than
the rest of the cohort, with a mean age of 27.2±4 years
vs 25.6±4.6 years (p<0.001). 27% of all Achilles
tendinopathies were reinjuries. A higher reinjury risk was
found after short recovery periods (31%) compared with
longer recovery periods (13%) (RR 2.4, 95% CI 2.1 to
2.8; p<0.001).
Conclusions Achilles tendon disorders account for
3.8% of the total lay-off time and are more common
in older players. Recurrence is common after Achilles
tendinopathies and the reinjury risk is higher after short
recovery periods.
INTRODUCTION
The elastic properties of the Achilles tendon are
important for locomotion.
13
The tendon has a
capacity to withstand loads up to 12.5 times the
body weight,
4
but nevertheless many athletes
sustain Achilles tendon disorders.
57
The cause of
Achilles tendon disorder is unclear,
8
but it is sug-
gested that the essential lesion of tendinopathy is a
failed healing response.
912
Achilles tendinopathy
often manifests with a gradual onset of pain during
tendon load (especially 26 cm proximal to the
tendon insertion),
13
morning stiffness and some-
times a localised swelling.
614
Achilles tendinopathies are often difcult to
treat, have a poor prognosis
13 15 16
and a tendency
to chronicity and recurrence,
17
with long periods
of absence from sports.
17 18
Achilles tendon disorders are frequently seen in
sports including running and jumping.
7 8 15 19 20
Achilles tendinopathy or an Achilles tendon rupture
can be career altering or career ending for profes-
sional athletes,
6172122
but only a few studies have
focused on Achilles tendon disorders in profes-
sional football players.
17 23 24
Woods et al
25
did
not report Achilles tendon disorders as a separate
diagnosis, but when evaluating ankle injuries
during two seasons in English professional football,
they found that 1% of all injuries were classied as
tendonitis or paratendonitis. Nearly one-third of
these occurred during the preseason period.
24
The present study investigated the incidence of
Achilles tendon disorders and the risk of reinjury in
a large population of elite male football players.
MATERIALS AND METHODS
Participants and study cohor t
The present study was performed within the frame-
work of the prospective injury study UEFA (Union
of European Football Associations) initiated among
male elite level football teams in 2001, the UCL
(UEFA Champions League) study.
26
This portion of
the study included 27 European professional foot-
ball teams from 10 countries. The teams were fol-
lowed over a varying number of seasons (111
seasons) between February 2001 and December
2011 and consisted of 1743 players (in an average
15 teams per season). All contracted players in the
rst team were invited to participate in the study.
Players who left the team during the season (eg,
because of transfer) were included during their
time on the team. Teams were followed during the
full season, including the preseason and competi-
tive season.
Data collection and study denitions
The study design followed the consensus on deni-
tions and data collection procedures in studies of
football injuries outlined in the consensus docu-
ment
27
and by UEFA
28
for studies of football. The
validation of the injury and exposure reporting
system and denitions has been described previ-
ously.
28
To ensure high reliability of data registra-
tion, all teams were provided with a study manual
describing the denitions used and procedures to
record data, including explanatory examples. To
avoid language problems, the manual and the study
Gajhede-Knudsen M, et al. Br J Sports Med 2013;47:763768. doi:10.1136/bjsports-2013-092271 1 of 6
Original article
forms were translated from English into ve other languages:
French, German, Italian, Russian and Spanish. In addition, the
study group checked all reports each month, and feedback was
sent to the teams correcting any missing or unclear data. The
denitions applied in the study are shown in table 1.
At the start of each season, player baseline data were col-
lected. Individual player participation in training and matches
(minutes of exposure) was recorded by the club contact person
on a standard exposure form sent to the study group on a
monthly basis. This included exposure with the rst and the
second teams, as well as any national team exposure, for all
players. The training content was not recorded. The team
medical staff recorded all time-loss injuries on a standard injury
form that was sent to the study group every month. The injury
form provided information about the diagnosis, nature and cir-
cumstances of injury occurrence. All injuries resulting in the
player being unable to fully participate in training or match play
(ie, time-loss injuries) were recorded, and the player was consid-
ered injured until the team medical staff allowed full participa-
tion in training and availability for match selection. Injuries
were categorised under of severity based on the number of
days of absence from training and/or match. All injuries were
followed until the nal day of rehabilitation.
The present study included all recorded Achilles tendon injur-
ies, including Achilles tendinopathies, partial Achilles tendon
ruptures and total Achilles tendon ruptures. The diagnosis was
based on the clinical examination by the team medical staff, and
no specic diagnostic criteria were set out in advance.
For the 48 severe injuries (>28 days lost) in 43 players, spe-
cic data about surgery and location of injuries were collected
retrospectively from the team doctors and the club medical
records.
Statistical analyses
Anthropometric data (age, height, body weight and body mass
index (BMI)) are presented with mean±SD and analysed with
independent sample t test. Lay-off time is presented with mean
±SD and corresponding median and quartiles (Q
1
(25th per-
centile) and Q
3
(75th percentile)). Owing to a skewed distribu-
tion in the lay-off time, group differences were analysed using
the Mann-Whitney U test. Pearsons χ
2
test was used to analyse
association between categorical variables. Injury rates are
reported as the number of injuries per 1000 player-hours and
injury burden was calculated as the number of lay-off days per
1000 player-hours. The rate ratio (RR) with 95% CI was used
for group comparisons of injury rates and injury burden, and
signicance was tested using z statistics. Seasonal trend,
expressed as the average annual percentage of change, was ana-
lysed using linear regression with log-transformed injury rates as
the dependent variables. A 2-year moving average (MA)
approach, by summarising two consecutive seasons, was also
used to smooth out the large seasonal variation. The reinjury
risk after the short (010 days) and long (>10 days) recovery
periods was compared using the risk ratio with 95% CI, and sig-
nicance was tested using z statistics. Season injury prevalence
was calculated as the number of injured players during a season/
total number of players in that season ×100. All tests were two-
sided and the signicance level was set at p<0.05.
The study design underwent an ethical review at Linköping
University, Linköping, Sweden and was approved by the UEFA
Football Development Division and the UEFA Medical
Committee.
RESULTS
Injury rates
In total, 1 057 201 h of exposure (888 249 h of training and
168 952 h of match play) were recorded. Overall, 8029 injuries
were documented during the study period, 203 (2.5%) of which
were Achilles tendon disorders. One hundred and ninety-four
(96%) disorders were classied as gradual onset tendinopathies,
and nine (4%) were acute onset partial or total ruptures. The
injury rate was almost 22 times higher in Achilles tendinopathies
compared with Achilles tendon ruptures (0.18 vs 0.01 injuries/
1000 h, RR 21.6, 95% CI 11.0 to 42.1; p<0.001). As the mean
total exposure time for a team of 28 players is about 7000 h per
season, a team can roughly expect one Achilles tendinopathy
every season, and one Achilles tendon rupture every 17th
season.
Between-season and within-season variation of injury rates
The injury rate of Achilles tendon disorders has uctuated,
between 0.12 and 0.35 injuries/1000 h, over the 11 seasons.
The highest injury rate was found in the February 2001 season
and the lowest notations were found in the 2006 and 2007
seasons. The crude injury rates and the smoother 2-year MA
injury rates are illustrated in gure 1. The MA approach indi-
cated an average annual decrease of 1.8% in the injury rate. The
tted regression model, however, indicated a non-signicant sea-
sonal trend in the log-transformed injury rates (R
2
=0.23, b=
0.056, 95% CI 0.131 to 0.020; p=0.132).
The within-season variation, measured as quarterly injury
rates, are shown in gure 2 and table 2. A higher injury rate was
found during the preseason ( JulyAugust) compared with the
competitive season (SeptemberMay), 0.25 vs 0.18 injuries/
1000 h (RR 1.4, 95% CI 1.1 to 2.0; p=0.027).
Table 1 Operational definitions used in the study
Training session Team training that involved physical activity under the
supervision of the coaching staff
Match Competitive or friendly match against another team
Injury Injury resulting from playing football and leading to a player
being unable to fully participate in future training or match
play (ie, time-loss injury)
Rehabilitation A player was considered injured until the team medical staff
allowed full participation in training and availability for
match selection
Index injury The first reported injury of each player is assumed to be an
index injury
Reinjury Injury of the same type and at the same site as an index
injury occurring not more than 2 months after a players
return to full participation from the index injury
Slight/minimal
injury
Injury causing absence of 03 days from training and match
play
Mild injury Injury causing absence of 47 days from training and match
play
Moderate injury Injury causing absence of 828 days from training and
match play
Severe injury Injury causing absence of over 28 days from training and
match play
Traumatic injury Injury with sudden onset and known cause
Overuse injury Injury with insidious onset and no known trauma
Injury rate Number of injuries per 1000 player-hours ((Σ injuries/Σ
exposure-hours)×1000)
Injury burden Number of days of absence per 1000 player-hours ((Σ days
of absence/Σ exposure-hours)×1000)
2 of 6 Gajhede-Knudsen M, et al. Br J Sports Med 2013;47:763768. doi:10.1136/bjsports-2013-092271
Original article
Injury severity and consequences
The severity of injuries and consequences in the form of lay-off
time and injury burden are shown in table 3. The mean lay-off
time for Achilles tendinopathies was 23±37 (median=10,
Q
1
=4 and Q
3
=24) days, while a rupture of the Achilles tendon,
on average, caused an almost seven times longer lay-off time,
with 161±65 (median=169, Q
1
=110 and Q
3
=189) days of
absence. Achilles tendon disorders account for 3.8% of the total
lay-off time reported in the study. The injury burden was
approximately three times higher in Achilles tendinopathies
compared with Achilles tendon ruptures (4.24 vs 1.37 days lost/
1000 h, RR 3.1, 95% CI 2.9 to 3.3; p<0.001).
Reinjuries
Twenty-seven per cent of all Achilles tendinopathies were reinju-
ries (table 3). No early recurrences were seen among the nine
Achilles tendon ruptures. The reported recurrence rate of all
injuries is 12% in the cohort. A higher reinjury risk was found
after short (010 days) recovery periods (31%) compared with
longer (>10 days) recovery periods (13%), (risk ratio 2.4, 95%
CI 2.1 to 2.8; p<0.001).
Anthropometric data
Players with Achilles tendon disorders were signicantly older
than the rest of the cohort, with a mean age of 27.2±4 years vs
25.6±4.6 years (p<0.001). No differences could be found in
height (182.1±6.2 cm vs 182.3±6.4 cm, p=0.607), body
weight (78.4±7.1 kg vs 78±7.1 kg, p=0.473) or BMI (23.6
±1.3 vs 23.4±1.4, p=0.092).
Location and treatment of severe injuries
Information about surgery and location was provided for 34 of
the 39 severe (>28 days lost) Achilles tendinopathies and infor-
mation about surgery was received for eight of the nine severe
Achilles tendon ruptures.
Twenty-three per cent of the proximal Achilles tendinopathies
were operated on (3/13), two of them with resection of the
plantaris tendon. Forty-ve per cent (9/20) of the insertional
tendinopathies were operated on. One player had surgery after
problems both in the main body and at the insertion. The mean
lay-off time for tendinopathy of the main body was 66±49
(median=43, Q
1
=35 and Q
3
=78) days, and for insertional ten-
dinopathies 79±50 (median=61, Q
1
=41 and Q
3
=109) days
(p=0.320). Surgery was performed on all seven total ruptures.
The partial rupture, from which we received information about
treatment, was not operated on.
DISCUSSION
A team of 28 players can roughly expect one Achilles tendon
disorder every season, and older players are more frequently
affected. Most absence periods for Achilles tendinopathies were
short (median of 10 days), but the recurrence rate was high
(27%). There was a signicantly higher risk of sustaining a rein-
jury if the player rested for less than 10 days. Finally, Achilles
tendinopathy was more common during the preseason period.
Achilles tendinopathies are common overuse injuries
Achilles tendon ruptures are rare
The season prevalence of Achilles tendinopathies in this study
was 2.15.1%. Woods et al
25
did not report Achilles tendon
Figure 1 Seasonal variations in
injury rates of Achilles tendon
disorders in male professional football
players.
Figure 2 Monthly variations in injury
rates of Achilles tendon disorders in
male professional football players.
Gajhede-Knudsen M, et al. Br J Sports Med 2013;47:763768. doi:10.1136/bjsports-2013-092271 3 of 6
Original article
disorders as a separate diagnosis, but when evaluating ankle
injuries during two seasons in English professional football, they
found that 1% of all injuries were classied as tendonitis or
paratendonitis. Fredberg et al
17
reported that 15% of the
players reported time loss attributable to Achilles tendinopathy
in Danish professional football players. The difference in injury
prevalence may reect a true difference in injury prevalence or
differences in study methodology, reporting thresholds or
varying treatment regiments (ie, to let players with symptoms
carry on playing or take them out of training). Achilles tendon
ruptures were rare at 0.01 injuries/1000 h of exposure.
Higher risk of Achilles tendinopathy during preseason
The incidence of Achilles tendon disorders was signicantly
higher during the preseason. All the teams in this cohort fol-
lowed an autumnspring season with preseason training in July
August, and a competitive season between September and May.
One team had a longer break between December and February
and contributed half the injuries in January, but the injury inci-
dence was still signicantly higher in the preseason.
More overuse, especially tendon injuries, occurs during the
preseason period.
24 2931
Woods et al
24
reported that 32% of
all Achilles tendon disorders occurred during the preseason, but
this study did not account for exposure, so the high number of
injuries could just reect more training sessions. The intense
preseason follows a period of rest. These sudden changes in
intensity, training load and training type are suggested to be risk
factors for overuse injuries such as Achilles tendinopa-
thies,
6714202432
because the Achilles tendon may not be able
to adapt fast enough to changes in loading pattern.
14
Varying absence periods for Achilles tendinopathy
The absence period for Achilles tendinopathy in this study
varied, with a median of 10 days and an average of 23 days.
Both Sankey et al
18
in rugby (mean=30 days) and Oztekin
et al
23
in Turkish professional football (median=30 days)
reported longer absences. This may reect differences in meth-
odology and in the demands of the sport.
The variations in lay-off time can be explained by the nature
of the injury. Achilles tendinopathy often manifests with a
gradual onset of pain,
61314
and it can be difcult to decide if
and when a player should rest. Many players continue to partici-
pate in training even with symptoms of Achilles tendinopa-
thy,
33 34
especially if they want to play an important match.
35
This affects the rehabilitation time needed. The players import-
ance to the team can also explain why some players rest less
than others.
Table 2 Achilles tendon disorders in the UCL cohort, comparison of preseason and competitive season in male professional football
Preseason Competitive season p Value
Achilles tendon disorders, n (percentage of total number of injuries) 54 (3.8) 149 (2.3) <0.001
Reinjuries, n (%) 17 (31) 36 (24) 0.306
Lay-off days, mean±SD 32±56 28±45 N/A
Lay-off days, median (Q
1
Q
3
)11(427) 10 (427) 0.964
Injury rate* (95% CI) 0.25 (0.19 to 0.33) 0.18 (0.15 to 0.21) 0.027
Training injuries 0.17 (0.12 to 0.24) 0.14 (0.11to 0.17) 0.302
Match injuries 0.81 (0.54 to 1.24) 0.37 (0.29 to 0.49) 0.003
Injury severity, n (%) 0.821
Slight/minimal (03 days) 13 (24) 28 (19)
Mild (47 days) 10 (19) 34 (23)
Moderate (828 days) 18 (33) 52 (35)
Severe (>28 days) 13 (24) 35 (23)
Injury burden (95% CI) 8.16 (7.78 to 8.55) 4.97 (4.82 to 5.12) <0.001
*Injury rate expressed as the number of injuries/1000 h of total exposure.
Injury burden expressed as the number of days of absence/1000 h of total exposure (injury rate×mean absence).
N/A, not applicable; Q
1
, 25th percentile; Q
3
, 75th percentile; UCL, UEFA Champions League.
Table 3 Achilles tendon disorders in the UCL cohort, comparison
of Achilles tendinopathies and Achilles tendon ruptures in male
professional football
Tendinopathies
Partial or
total ruptures
Achilles tendon disorders,
n (percentage of total
number of injuries)
194 (2.4) 9 (0.1)
Reinjuries, n (%) 53 (27) 0 (0)
Lay-off days, mean±SD 23±37 161±65
Index injury 20±34 161±65
Reinjury 32±44 N/A
Lay-off days, median (Q
1
Q
3
)10(424) 169 (110189)
Index injury 8 (421) 169 (110189)
Reinjury 14 (437) N/A
Injury rate* (95% CI) 0.18 (0.16 to 0.21) 0.01 (0.00 to 0.02)
Injury severity, n (%)
Slight/minimal (03 days) 41 (21)
Mild (47 days) 44 (23)
Moderate (828 days) 70 (36)
Severe (>28 days) 39 (20) 9 (100)
Injury burden (95% CI) 4.24 (4.12 to 4.37) 1.37 (1.30 to 1.44)
Days of absence/player/season,
mean±SD
1.0±10.5 0.3±7.8
Season prevalence, range 2.1 to 5.1 0.0 to 0.5
*Injury rate expressed as the number of injuries/1000 h of total exposure.
Injury burden expressed as the number of lay-off days/1000 h of total exposure
(injury rate×mean absence).
Season prevalence expressed as the number of players with an injury in a season/
total number of players in that season×100.
N/A, not applicable; Q
1
, 25th percentile (first quartile, 25%); Q
3
, 75th percentile
(third quartile, 75%); UCL, UEFA Champions League.
4 of 6 Gajhede-Knudsen M, et al. Br J Sports Med 2013;47:763768. doi:10.1136/bjsports-2013-092271
Original article
Achilles tendon ruptures cause long absences from football
The median absence period for the Achilles tendon rupture in
this study was 169 days (mean=161). Both professional rugby
players (mean=185.5 days)
18
and professional Turkish football
players (median and mean=180 days)
23
reported longer
absences. This may result from differences in methodology and
study size, or in rugby, differences between sports. Also, with
only nine ruptures in 11 years, the average is vulnerable to
outliers.
Six of the nine players sustaining ruptures of the tendon had
been followed in our study before the season when the rupture
occurred, and none of these players had any Achilles disorders
resulting in time loss before their rupture. Symptoms before
ruptures are reported to vary between 10% and 25%.
19 3638
Since degenerative changes are found in almost all ruptured
tendons,
38
it seems plausible that tendons undergo changes
during an asymptomatic period of several months, where the
tendon might be injured but the player does not experience
symptoms, before the pathology results in pain and the changes
become symptomatic.
17 38
Therefore, some tendons might
rupture before signs of Achilles tendinopathy occur.
38
Short absence time increases the risk of reinjury
The high recurrence rate for Achilles tendinopathy found in this
study (27%) reects the chronic and recurrent character of this
condition. The frequent relapse of symptoms when players
return to football after a short rehabilitation period could be
explained if pain is only the tip of the iceberg. Even if pain
recedes to below the threshold, the pathological changes in the
tendon could still exist and could therefore become symptom-
atic when the player resumes his activity level.
14
Players who
abstained from training and matches for less than 10 days at
their index injury experienced a signicantly higher risk of rein-
jury than players who rested for more than 10 days (p<0.001).
Inadequate rehabilitation, with a premature return to activity, is
a risk factor for reinjury.
30 39 40
Therefore, it could be suggested
that a longer rehabilitation period at the rst signs of Achilles
tendinopathy could be benecial to avoid recurrences. A func-
tional test before returning to play might also reduce
recurrences.
41
There is little evidence on how to prevent these recurrences.
Fredberg et al
17
showed that prophylactic eccentric and stretch-
ing exercises did not reduce the frequency of ultrasonographic
abnormalities in Achilles tendons in professional football
players. On the other hand, the lack of effect might be because
the training was not intense enough (2.25 times/week).
17
Older players sustain Achilles tendinopathy
The players who sustained an Achilles tendon disorder were sig-
nicantly older than the rest of the cohort (27.2 vs 25.6 years),
as reported in other studies.
622
The incidences of muscle calf
injuries increase with age
42
and, if the calf muscle is more
exposed to injury, this could affect the risk of injury in the
Achilles tendon as well. Further, it is well established that pro-
longed, strenuous endurance exercise induces muscle damage
and impairs muscle function.
43
Normally, the muscle tendon
unit is able to repair and adapt, but there might be a limit to the
regenerative capacity and adaptability, resulting in pathology.
44
If the calf muscles of older players theoretically have impaired
function, there is a risk that the muscles become more easily
fatigued. Fatigued muscles lose their ability to absorb shock,
6
which theoretically can put a greater stress on the Achilles
tendon.
Treatment of the severe injuries
In accordance with other studies, all the total Achilles tendon
ruptures in this study were managed surgically.
18 23
Many
Achilles tendinopathies can be treated conservatively, but around
25% require surgery.
20 45
Of the severe (>28 days lost) tendino-
pathies in the present study, 38% were operated on.
Most severe tendinopathies in this study were located at the
insertion (20 of the 34 we had information about). The inser-
tional lesions also required surgery more often (45% vs 23%)
and caused longer absences from football than the proximal
lesions (mean=79 vs 66 days).
Methodological considerations
The prospective design and the 11-season study period are the
strengths of the present study, together with the large and
homogeneous sample of professional footballers.
However, this study also has some limitations. First, no treat-
ment details were requested on the general injury card.
Additionally, no substudy specic injury card was sent to the
clubs as was done for some of our previous substudies.
Distinction between insertional and proximal Achilles tendon
disorders was therefore not possible, which was a limitation in
the study. We did, however, retrospectively collect data about
the location and surgery for injuries causing an absence of
greater than 28 days and since most clubs preserve les with
objective data such as images and surgery protocols of previous
injuries, we did receive data for most of these injuries.
Second, our study manual did not provide the participating
clubs with specic diagnostic or return-to-play criteria: it is
therefore possible that the reported subclassications, lay-off
times and reinjury rates varied between clubs due to different
diagnostics and treatment algorithms. Third, no reliable history
of injury was collected at player inclusion; it was therefore not
possible to compare the rates of Achilles disorders between
uninjured players and players with prior Achilles disorders.
Fourth, with the current time-loss denition, the number of
overuse injuries, such as Achilles tendinopathy, captured in this
surveillance study might only be the tip of the iceberg.
45
Overuse injuries might be underestimated, because many players
with Achilles tendinopathy keep participating in training and
matches despite having problems, and are therefore not cap-
tured in our time-loss denition.
35 45
However, this denition
was chosen for the general injury surveillance study to capture
the injuries, which had a substantial effect on the players and
the teams ability to perform.
35
What are the new ndings?
Achilles tendon disorders account for 2.5% of all injuries
and 3.8% of lay-off times in male professional football.
Achilles problems are more common in older players.
A majority (96%) of the disorders are gradual onset
tendinopathies, and 4% are acute onset partial or total
ruptures.
The incidence of Achilles disorders is higher during the
preseason compared with the competitive season.
The median lay-off time for Achilles tendinopathies is
10 days and for ruptures it is 169 days.
Twenty-seven per cent of Achilles tendinopathies are
reinjuries and these are more common after short (>10 days)
recovery periods.
Gajhede-Knudsen M, et al. Br J Sports Med 2013;47:763768. doi:10.1136/bjsports-2013-092271 5 of 6
Original article
How might it impact on clinical practice in the near
future?
Players with Achilles tendinopathies might need longer
recovery periods since the reinjury risk is signicantly higher
after recovery periods of less than 10 days.
The team medical and coaching staffs should be aware of
the increased risk of Achilles problems during the preseason
training period and observant of overuse to Achilles
tendons.
The team medical and coaching staffs should be observant
of the higher risk of older players who suffer from
muscle-tendon problems after repetitive hard training
sessions.
Acknowledgements The authors would like to thank the participating clubs,
medical staffs and players.
Contributors JE was responsible for the conception and design of the study. HM
has been the statistical advisor and revised the paper. MGK wrote the rst draft of
the manuscript, which was critically revised by NM, HM and JE. All authors
contributed to the interpretation of the ndings and approved the nal draft of the
manuscript. JE is the study guarantor.
Funding This study was supported by grants from the Union of European Football
Associations (UEFA), the Swedish National Centre for Research in Sports and
Praktikertjänst AB.
Competing interests None.
Patient consent Obtained.
Ethics approval The study design underwent an ethical review at Linköping
University, Linköping, Sweden and was approved by the UEFA Football Development
Division and the UEFA Medical Committee.
Provenance and peer review Not commissioned; externally peer reviewed.
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Original article
... 1,2,19,27,35 However, the performance data for RTP after ATRs in professional soccer remains sparse. In a study of the Union of the European Football Association (UEFA) Champions League, Gajhede-Knudsen et al 10 found the incidence of Achilles tendinopathy to be 0.18 injuries per 1000 hours and the incidence of ATR to be 0.01 per 1000 hours, with ATRs resulting in 161 ± 65 days of lost playing time. The authors did not investigate performance metrics as an outcome of interest, despite evidence of long-term healing. ...
... The mean layoff after ATR has been reported to be 161 days among professional soccer players and 4.8 months for elite athletes. 10,22 Additionally, we found that 71% of injured players returned to high-level play within the first postoperative year and 78% returned at any timepoint. Previous investigations have demonstrated similar outcomes in the context of ATR. ...
... Interestingly, 1 investigation found shorter recovery periods to be significantly associated with reinjury, highlighting the importance of adhering to rehabilitation timelines to allow adequate healing of the repair. 10 The present investigation found the mean age of ATR among professional soccer players to be 27.49 years. ...
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Background Achilles tendon rupture (ATR) is a potentially career-ending injury in professional athletes. Limited information exists regarding return to play (RTP) in professional soccer players after this injury. Purpose To determine the RTP rate and time in professional soccer players after ATR and to evaluate player performance relative to matched controls. Study Design Cohort study; Level of evidence, 3. Methods We evaluated 132 professional soccer players who suffered an ATR between 1999 and 2018. These athletes were matched 2:1 to uninjured controls by position, age, season of injury, seasons played, and height. We collected information on the date of injury, the date of RTP, and player performance metrics (minutes played, games played, goals scored, assists made, and points per game) from official team websites, public injury reports, and press releases. Changes in performance metrics for the 4 years after the season of injury were compared with metrics 1 season before injury. Univariate comparisons were performed using independent-sample, 2-group t tests and Wilcoxon rank-sum tests when normality of distributions was violated. Results The mean age at ATR was 27.49 ± 4.06 years, and the mean time to RTP was 5.07 ± 2.61 months (18.19 ± 10.96 games). The RTP rate was 71% for the season after injury and 78% for return at any timepoint. Overall, 9% of the injured players experienced a rerupture during the study period. Compared with controls, the injured players played significantly less (-6.77 vs -1.81 games [ P < .001] and -560.17 vs -171.17 minutes [ P < .05]) and recorded fewer goals (-1.06 vs -0.29 [ P < .05]) and assists (-0.76 vs -0.02 [ P < .05]) during the season of their Achilles rupture. With the exception of midfielders, there were no significant differences in play time or performance metrics between injured and uninjured players at any postinjury timepoint. Conclusion Soccer players who suffered an ATR had a 78% RTP rate, with a mean RTP time of 5 months. Injured players played less and demonstrated inferior performance during the season of injury. With the exception of midfielders, players displayed no significant differences in play time or performance during any of the 4 postinjury seasons.
... 4 Despite favorable longterm outcomes with progressive loading, approximately half of those with Achilles tendinopathy will experience either symptom persistence or recurrence. [5][6][7][8] Accelerated return-to-sport (RTS) appears to increase the risk of symptom recurrence, 5 underpinning the importance of a structured RTS phase during rehabilitation. Yet, it is currently unclear what measures should be used by clinicians, patients, and other stakeholders when progressing those with Achilles tendinopathy through the RTS phase. ...
... 4 Despite favorable longterm outcomes with progressive loading, approximately half of those with Achilles tendinopathy will experience either symptom persistence or recurrence. [5][6][7][8] Accelerated return-to-sport (RTS) appears to increase the risk of symptom recurrence, 5 underpinning the importance of a structured RTS phase during rehabilitation. Yet, it is currently unclear what measures should be used by clinicians, patients, and other stakeholders when progressing those with Achilles tendinopathy through the RTS phase. ...
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We aimed to 1) compare pain, tendon structure, lower limb function, and Achilles tendon loads while running between limbs in runners with Achilles tendinopathy, and 2) explore the relations of pain, tendon structure, and lower limb function to Achilles tendon loads while running. Twenty runners with Achilles tendinopathy participated in this pilot study. Pain was assessed with questionnaires, quantitative sensory testing, and functional testing. Tendon morphology and mechanical properties were evaluated with ultrasound imaging, continuous shear wave elastography, and ultrasound imaging combined with dynamometry. Lower limb function was assessed with an established test battery. Achilles tendon loads were estimated from biomechanical data acquired during running. Compared to the least symptomatic limb, the most symptomatic limb had lower scores on the Victorian Institute of Sports Assessment – Achilles questionnaire and worse pain during drop countermovement jumping, hopping, and running. Tendon thickness and cross‐sectional area were greater, and Young’s modulus, drop countermovement jump height, and plyometric quotient during hopping were lower on the most symptomatic limb. Side‐to‐side differences in drop countermovement jump height were significantly associated with side‐to‐side differences in Achilles tendon peak forces and average loading rates during running. Various measures of pain, structure, and function differ between limbs in runners with Achilles tendinopathy during return‐to‐sport. Tendon forces, however, do not differ between limbs during comfortable running. In addition to measures that differ between limbs, measures of performance during drop countermovement jumping may aid in clinical decision‐making during return‐to‐sport because they are associated with tendon forces while running.
... Recovery of an adequate tendon load-bearing capacity is mandatory among athletes, particularly due to the high risk of recurrence of tendinopathy observed after early return to Medicina 2021, 57, 1088 2 of 10 sport [6]. Currently, recommended treatment strategies are extremely variable [1]. ...
... Recovery of an adequate tendon load-bearing capacity is mandatory among athletes, particularly due to the high risk of recurrence of tendinopathy observed after early return to sport [6]. Currently, recommended treatment strategies are extremely variable [1]. ...
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Tendinopathy is a complex clinical condition with a rising incidence and prevalence, particularly during sports practice. For the return to play in affected patients, adequate functional and structural recovery of the tendon is the ultimate goal, avoiding the high risk of recurrence. In this perspective, local therapies alongside exercise are showing promising results. Despite evidence suggesting hyaluronic acid (HA) injections as effective in the treatment of tendinopathy, current recommendations about the management of this condition do not include this intervention. HA seems to be an effective therapeutic option for the management of sport-related tendinopathies, but further studies with a larger sample size are needed to confirm available findings. In this narrative review, we analyzed available literature about the rationale of the use of HA in the management of tendon injury and, particularly, in sport-related tendinopathies.
... Gajhede-Knudsen et al. conducted a series of three experiments in 2013 to screen the video of badminton matches in time and space and to explore the ability of judging the batting mode in different levels of badminton matches. e results showed that the judgment ability of novice badminton game decreased significantly after the amount of information of batting in the video was reduced [20]. In the same year, Abian-Vicen et al. studied the difference in prejudging ability of receiving badminton matches in different levels through space blocking technology. ...
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... Players of both sexes showed a high percentage of training contents aimed at injury prevention. Considering the reduction of the conditioning-dependent properties of tissues, especially tendons and muscles, as well as the mismatches of neuromuscular control, several authors have suggested the need to provide different types of stresses (Buchheit & Laursen, 2013b;Gajhede-Knudsen, Ekstrand, Magnusson, & Maffulli, 2013) to maintain structural adaptations, and different types of speeds and movements to guarantee the functionality of the tendon (Kubo, Ikebukuro, Yata, Tsunoda, & Kanehisa, 2010). Speed was one of the contents to which less importance was given in the training programs, although it is known that a single week of training cessation can reduce the performance of speed resistance in trained soccer players (Joo, 2018). ...
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... Although the tipping point where match exposure shifts from having a protective effect against injuries to a detrimental impact is likely to be influenced by a complex range of factors and is currently unknown, it is clear that playing a subsequent match within 24 hours is uniquely detrimental to player welfare beyond other intermatch intervals. An additional hypothesis is that players who had not played because of injury in the previous 7-14 days were at a higher risk of injury when returning to match play perhaps as a consequence of premature return to play [36][37][38]. ...
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... A retrospective review of male soccer players in any of the 5 major European soccer leagues (English Premier League, Bundesliga, Serie A, La Liga, and Ligue 1) was conducted from 2000 to 2016 via a publicly available database, as established in previous investigations. 10,12,24,[37][38][39] Players with traumatic fractures involving the femur, the tibia, and/or the fibula were identified for inclusion in the LE fracture cohort. Players with no recorded injury of the LE were identified for inclusion in the control cohort. ...
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To conduct a comprehensive systematic review and meta-analysis of studies assessing the prevalence of Achilles tendinopathy (AT) in physical exercise (PE). Specifically, we estimate the overall risk of AT in physical exercise and compare sport-specific estimates of AT risk. Four databases (PubMed, Web of Science, Cochrane Library, SPORTDiscus) were searched before 1st October 2021. Random-effects, subgroup analysis, sensitivity analysis and meta-regressions were conducted, involving 16 publications. This meta-analysis found that the overall prevalence of AT was 0.06 (95% CI, 0.04–0.07). The prevalence of Achilles tendon rupture was 0.03 (95% CI, 0.02–0.05). Subgroup analysis showed that the prevalence of AT increased with age, the highest among the group aged over 45 (0.08; 95% CI, 0.04–0.11), and the lowest among the group under 18 years old (0.02; 95% CI, 0.01–0.03). The two sport events with the highest prevalence of AT were gymnastics and ball games, at (0.17; 95% CI, 0.14–0.20) and (0.06; 95% CI, 0.02–0.11), respectively. The prevalence of AT in athletes (0.06; 95% CI, 0.04–0.08) was higher than that of amateur exercisers (0.04; 95% CI, 0.02–0.06) and there was no difference in prevalence of AT between male and female. There are differences in the prevalence of AT in different ages, sport events and characteristics of participants. This systematic review and meta-analysis suggested that it was necessary to pay more attention on AT in the people who were older or engaged in gymnastics.
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Background Acute Achilles tendon ruptures (AATRs) that occur in athletes can be a career-ending injury. The aim of this study was to describe return to play and clinical outcomes of isolated endoscopic flexor hallucis longus (FHL) transfer in active soccer players with AATR. Methods Twenty-seven active male soccer players who underwent endoscopically assisted FHL tendon transfer for acute Achilles tendon ruptures were included in this study. Follow up was 46.2 (±10.9) months after surgery. Return to play criteria and clinical outcome measures were evaluated. Results All players returned to playing professional competitive soccer games. Return to active team training was at a mean of 5.8 (±1.1) months postoperatively. However, return to active competitive match play occurred at a mean of 8.3 (±1.4) months. Twenty-two players (82%) were able to return to their preinjury levels and performances and resumed their professional careers at the same soccer club as their preinjury state. One player (3.7%) shifted his career to professional indoor soccer. At 26 months postoperatively, the mean Tegner activity scale score was 9.7 (±0.4), the mean Achilles tendon total rupture score was 99 (±2), and the mean American Orthopaedic Foot & Ankle Society ankle-hindfoot score was 99 (±3). No patients reported any great toe complaints or symptomatic deficits of flexion strength. Conclusion The current study demonstrated satisfactory and comparable return to play criteria and clinical results with minimal complications when using an advanced endoscopically assisted technique involving FHL tendon transfer to treat acute Achilles tendon ruptures in this specific subset of patient cohort. Level of Evidence Level II, prospective cohort case series study.
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