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Knee injuries – diagnostics, treatment and prevention.

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Abstract

Dansk Sportsmedicin, 2012;4:24-26.
DANSK SPORTSMEDICIN • Nr. 4, 16. årg., NOVEMBER 2012
24 Fagligt
Knee injuries – diagnostics,
treatment and prevention
Markus Waldén, MD, PhD & Martin Hägglund, RPT, PhD
Football Research Group & Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
Abstract
Anterior cruciate ligament (ACL) in-
jury is the knee injury in football that
probably draws the most attention.
Many risk factors for ACL injury are
suggested in the literature, but the
knowledge about potential football-
specic risk factors is limited. Brie-
y, match play is associated with a
considerably higher ACL injury rate
than training, previous ACL injury is
associated with an increased rate of a
future ACL injury, female footballers
are more susceptible to ACL injury
compared to their male counterparts,
and female players also tend to sustain
their ACL injury at younger ages than
males. Fortunately, there is upcoming
evidence that many ACL injuries can
be prevented. In a recent cluster ran-
domised controlled trial in female ado-
lescent football, a coach-led 15-minute
neuromuscular warm-up programme
carried out twice a week during the
season resulted in a 64% reduction in
ACL injury rate.
Introduction
Football is the most popular sport
worldwide with more than 260 million
active players according to the FIFA
Big Count survey in 2006 (www.fa.
com). The knee injury rate in football
is known to be high and the injury that
probably draws the most attention is
the anterior cruciate ligament (ACL)
injury. However, ACL injury is not a
very common football injury, occurring
to between 0.5 and 6.0% of all female
players and between 0.6 and 8.5% of all
male players annually depending on
the setting (10). This article is a sum-
mary of the lecture on “Knee injuries
– diagnostics, treatment and preven-
tion” held at the Football Symposium
in Copenhagen on September 08, 2012.
The purpose of this short report is to
summarise the current football lite-
rature on ACL injury regarding risk
factors, return to play rates, and injury
prevention with personal reections
from our own research in the Football
Research Group in Linköping, Sweden.
Risk factors
Many risk factors for ACL injury are
proposed in the literature (8), and
they are usually divided into extrinsic
(environmental) and intrinsic (indivi-
dual) factors. These factors can further
be classied as modiable (e.g. body
mass) or non-modiable (e.g. age)
which might be of importance when
targeting injury prevention. A sum-
mary of the most commonly suggested
risk factors are seen in Table 1. Even if
numerous risk factors have been sug-
gested, studies about potential foot-
ball-specic risk factors are few, and
reliable scientic support can only be
found for activity type (extrinsic risk
factor), and previous injury, sex and
age (intrinsic risk factors).
Activity type
Match play is associated with a con-
siderably increased ACL injury rate
compared to training and studies have,
irrespective of sex, reported up to 65
times higher ACL injury rate in match
play than in training (10).
Previous injury
Previous injury is a well-known risk
factor for many different sports inju-
ries, including ACL injury. In a study
on the German female elite league
players with prior ACL injury had a
5-fold increased rate of a future ipsi-
lateral graft tear or contralateral ACL
injury (2).
Sex
Female athletes participating in jum-
ping, cutting and pivoting team sports
such as football, handball and basket-
ball are often claimed to have a 4-6
times higher ACL injury rate compared
to their male counterparts (3). The
female-to-male ACL injury rate ratio in
football has recently been reviewed in
two studies (7, 10). According to these
reviews, however, female footballers
are only up to 3 times more suscepti-
ble to ACL injury compared to their
male counterparts. In the rst study,
the pooled female-to-male ACL injury
rate ratio from 5 studies included in a
meta-analysis was 2.67 (7). In the se-
cond study, 13 studies were included
in a structured literature review with
the majority of the studies reporting
a 2- to 3-fold higher ACL injury rates
among females (10). Interestingly, only
one study reported more than a 4 times
higher rate in females and the gender
disparity seems to be more associated
DANSK SPORTSMEDICIN • Nr. 4, 16. årg., NOVEMBER 2012
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with injury rates during match play
and not during training (10).
Age
ACL injury is rare in pre-pubertal
children, and no difference in ACL
injury rate has been found between
girls and boys up to 12 years-of-age (9).
Even if the number of studies that have
reported the average age at injury is
limited, all studies to date have consi-
stently shown that female players are
younger when they sustain their ACL
injury (10). In addition, female late pu-
bertal or early post-pubertal teenagers
seem to be at highest risk (4). Age is
therefore most likely a confounding
factor when calculating female-to-male
ACL injury rate ratios in sports. This
phenomenon is best illustrated by re-
ferring to the example reported in a re-
cent study on the Swedish female and
male elite leagues (11). In that study,
the crude female-to-male ACL injury
rate ratio was 2.6, but after adjusting
for differences in age between the sexes
this ratio was lowered to 2.1, which
thus should be regarded as the “true”
female-to-male ACL injury rate ratio.
In our opinion, the notion that female
athletes participating in jumping, cut-
ting and pivoting team sports have
an up to 6-fold higher ACL injury rate
compared to their male counterparts
should therefore be questioned.
Return to play
In a study on 57 professional/elite
football clubs with 2329 players fol-
lowed over a varying number of sea-
sons from 2001 to 2009, a total of 76
male and female players suffered 78
ACL injuries (11). The majority of the
players with total tears in that study
returned to training within 10 months
after surgery (94%) and participated
in match play within 12 months after
surgery (89%). Up to now, prospective
data for 111 ACL injuries have been
collected between 2001 and 2011 (new
unpublished data). Interestingly, all
57 players with ACL injuries occur-
ring in the so-called UEFA Champions
League study returned to play at the
same level as prior to the injury (100%),
whereas 95% of players in the Swedish
male elite league (Allsvenskan) and
87% in the Swedish female elite league
(Damallsvenskan) returned to football,
respectively. These  gures are thus in
contrast to the average return to sports
rate (at the previous competition level)
after ACL injury that was recently re-
ported to be 63% in a review of 48 in-
dividual studies (1). In our experience,
the underlying reasons to the high
return to play success rates in high-
level football are probably multi-fac-
torial and include  nancial incentives,
referral to experienced high-volume
knee surgeons (“centralised” ACL re-
constructive surgery), use of magnetic
resonance imaging on a routine basis to
obtain an established diagnosis imme-
diately, proper treatment of any associ-
ated joint injuries, and individualised
daily physical therapy by the club phy-
siotherapist and rehabilitation team.
The mean lay-off period was 6.9
months (209 days) to the  rst full
training session without restrictions
(“medical clearance” from club medical
staff) and another month to the  rst
match appearance (245 days). If this
7-8 months lay-off period is the time it
actually takes to come back to the pitch
at the professional/elite level, it is, in
our opinion, unrealistic to expect that
a non-elite youth or amateur player
should be able to return to play after
approximately 6 months, which is the
most commonly recommended rehabi-
litation time advocated by many knee
surgeons.
ACL-injury prevention
Several parallel-group controlled stu-
dies have been conducted in football to
evaluate injury-prevention strategies,
most targeting female adolescents (4).
However, only two non-randomised
studies in adolescent football show sig-
ni cant reduction of acute knee injuries
or non-contact ACL injuries with neu-
romuscular warm-up programmes (5,
6). Importantly, most studies were not
designed to speci cally evaluate pre-
ventive effects on knee or ACL injury
as the primary outcome, and there has
been a lack of high-quality randomised
controlled trials targeting prevention of
these injuries.
DANSK SPORTSMEDICIN • Nr. 4, 16. årg., NOVEMBER 2012
26 Fagligt
We therefore conducted a strati ed
cluster randomised controlled trial in
female adolescent football evaluating
a coach-led 15-minute neuromuscular
warm-up programme targeting core
stability, balance, strength and proper
knee alignment (12). The neuromuscu-
lar warm-up programme (Knäkontroll,
SISU Idrottsböcker©, Sweden, 2005)
was intended to be carried out twice a
week throughout the competitive sea-
son in 2009 in the intervention group
clubs, whereas the control group clubs
trained as usual. In total, 309 clubs in
Sweden with female players aged 12-17
years were randomised and 230 clubs
with 4564 players were included for
analysis, making it the largest rando-
mised controlled trial in sports injury
prevention to date. Brie y, 21 players
suffered an ACL injury during the
season and, by intention-to-treat analy-
sis, we found a 64% reduction in ACL
injury rate in the intervention group
(Table 2). No signi cant rate reductions
were seen for the secondary outcomes
acute knee injury and severe knee
injury (Table 2). However, sub-group
analyses of players who carried out the
neuromuscular warm-up programme
at least once a week over the season
(“compliers”) showed signi cant redu-
ctions in all outcomes; ACL injury 83%,
severe knee injury 82%, and any acute
knee injury 47%.
References
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Correspondence to:
Dr Markus Waldén
Department of Medical
and Health Sciences
Linköping University
581 83 Linköping, Sweden
Tel: + 46 733 920 720
E-mail: markus.walden@telia.com
ResearchGate has not been able to resolve any citations for this publication.
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