The UEFA injury study: 11-year data concerning 346 MCL injuries and time to return to play

Abstract

Background Medial collateral ligament (MCL) injury is the most common knee ligament injury in professional football.
Aim To investigate the rate and circumstances of MCL injuries and development over the past decade.
Methods Prospective cohort study, in which 27 professional European teams were followed over 11 seasons (2001/2002 to 2011/2012). Team medical staffs recorded player exposure and time loss injuries. MCL injuries were classified into four severity categories. Injury rate was defined as the number of injuries per 1000 player-hours.
Results 346 MCL injuries occurred during 1 057 201 h (rate 0.33/1000 h). The match injury rate was nine times higher than the training injury rate (1.31 vs 0.14/1000 h, rate ratio 9.3, 95% CI 7.5 to 11.6, p<0.001). There was a significant average annual decrease of approximately 7% (p=0.023). The average lay-off was 23 days, and there was no difference in median lay-off between index injuries and reinjuries (18 vs 13, p=0.20). Almost 70% of all MCL injuries were contact-related, and there was no difference in median lay-off between contact and non-contact injuries (16 vs 16, p=0.74).
Conclusions This largest series of MCL injuries in professional football suggests that the time loss from football for MCL injury is 23 days. Also, the MCL injury rate decreased significantly during the 11-year study period.

Full text

The UEFA injury study: 11-year data concerning
346 MCL injuries and time to return to play
Matilda Lundblad,
1,2
Markus Waldén,
1,2
Henrik Magnusson,
2,3
Jón Karlsson,
4
Jan Ekstrand
1,2,5
1
Division of Community
Medicine, Department of
Medical and Health Sciences,
Linköping University,
Linköping, Sweden
2
Football Research Group,
Linköping University,
Linköping, Sweden
3
Division of Physiotherapy,
Department of Medical and
Health Sciences, Linköping
University, Linköping, Sweden
4
Department of Orthopaedics,
Sahlgrenska University,
Gothenburg, Sweden
5
UEFA Medical Committee,
Nyon, Switzerland
Correspondence to
Professor Jan Ekstrand,
Football Research Group
Solstigen 3, Linköping
University, Linköping S-589 43,
Sweden; Jan.ekstrand@telia.
com
Accepted 29 March 2013
Published Online First
26 April 2013
To cite: Lundblad M,
Waldén M, Magnusson H,
et al.Br J Sports Med
2013;47:759–762.
ABSTRACT
Background Medial collateral ligament (MCL) injury is
the most common knee ligament injury in professional
football.
Aim To investigate the rate and circumstances
of MCL injuries and development over the past decade.
Methods Prospective cohort study, in which
27 professional European teams were followed over
11 seasons (2001/2002 to 2011/2012). Team medical
staffs recorded player exposure and time loss injuries.
MCL injuries were classified into four severity categories.
Injury rate was defined as the number of injuries per
1000 player-hours.
Results 346 MCL injuries occurred during 1 057 201 h
(rate 0.33/1000 h). The match injury rate was nine times
higher than the training injury rate (1.31 vs 0.14/1000 h,
rate ratio 9.3, 95% CI 7.5 to 11.6, p<0.001). There was
a significant average annual decrease of approximately
7% (p=0.023). The average lay-off was 23 days, and
there was no difference in median lay-off between index
injuries and reinjuries (18 vs 13, p=0.20). Almost 70% of
all MCL injuries were contact-related, and there was no
difference in median lay-off between contact and non-
contact injuries (16 vs 16, p=0.74).
Conclusions This largest series of MCL injuries in
professional football suggests that the time loss from
football for MCL injury is 23 days. Also, the MCL injury
rate decreased significantly during the 11-year study
period.
INTRODUCTION
The overall injury rate of professional footballers is
approximately 1000 times higher than that of
typical industrial occupations, generally regarded as
high risk.
1
Several studies have investigated the
injury epidemiology in high-level football,
2–8
but
few have reported the data on medial collateral
ligament (MCL) injuries. After hamstring injury,
MCL injury is the most common severe injury
subtype.
2
The objective of this study was to investigate the
rate and circumstances of MCL injuries and their
development over the past decade. The hypotheses
of this study were that the MCL injury rate
decreased during the study period and that MCL
injuries are more frequently caused by contact
mechanisms.
MATERIAL AND METHODS
A prospective cohort study of professional men’s
football in Europe has been carried out since 2001
in collaboration with the Union of European
Football Associations (UEFA): the UEFA
Champions League study.
2
For the purpose of this
study, 27 European teams (1743 players) were fol-
lowed for 11 seasons from 2001 to 2012.
3
All con-
tracted players in the first teams were invited to
participate in the study. The mean squad size was
25 players.
3
Study design and definitions
The full methodology and the development of the
study design have been reported elsewhere.
9
The
study design followed the consensus on definitions
and data collection procedures in studies of football
injuries.
10
Specifically for this study, MCL injury
was defined as ‘a traumatic distraction injury to the
superficial MCL (sMCL), deep MCL (dMCL) and
the posterior oblique ligament (POL) leading to a
player being unable to participate fully in training
or match play’. General definitions are given in
table 1.
Data collection
Player baseline data were collected once a year at
player inclusion. Individual player exposure in
training and matches was registered by the clubs on
a standard exposure form sent to the study group
on a monthly basis. The teams’medical staff
recorded injuries on a standard injury form that
was also sent to the study group each month. The
injury form provided the information about the
diagnosis, nature and circumstances of injury occur-
rence, for example. All injuries resulting in a player
being unable to participate fully in training or
match play (ie, time loss injuries) were recorded.
The player was regarded as injured until the team
medical staff allowed full participation in training
and availability for match selection. All injuries
were followed until the final day of rehabilitation.
Contact/non-contact was recorded on the injury
form from 2004 to 2005, match minute of injury
from 2005 to 2006 and injury mechanisms from
2008 to 2009.
Statistical analyses
Lay-off time is presented as the mean±SD and the
corresponding median and quartiles (Q
1
=25
th
per-
centile and Q
3
=75
th
percentile). Owing to skewed
distribution in lay-off time, group differences were
analysed using the Mann-Whitney U test. Pearson’s
χ
2
test was used to analyse the association between
categorical variables. Injury rate was 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 a 95% CI was used for group compari-
sons of injury rates and injury burden, while signifi-
cance was tested using z-statistics.
11
Seasonal trend,
Lundblad M, et al.Br J Sports Med 2013;47:759–762. doi:10.1136/bjsports-2013-092305 1 of 5
Original article

expressed as the average annual percentage of change, was ana-
lysed using linear regression with log-transformed injury rates as
the dependent variable. A 2-year moving average approach, by
summarising two consecutive seasons, was also used to smooth
out large seasonal variation. A one-sample proportional z-test
was used to analyse the differences between 15 min periods in
matches. All tests were two-sided and the significance level was
set at p<0.05.
RESULTS
In all, 10 57 201 h of exposure (8 88 249 h of training and
1 68 952 h of match play) were registered. In overall terms, 8029
injuries were documented, 346 (4.3%) of which were MCL injuries.
The total MCL injury rate was 0.33/1000 h (table 2); a team of 25
players can therefore expect roughly two MCL injuries every
season. The match injury rate was nine times higher than the train-
ing injury rate (1.31 vs 0.14/1000 h, RR 9.3, 95% CI 7.5 to 11.6,
p<0.001).
Between-season and within-season variation
The MCL injury rate fluctuated between 0.19 and 0.57/1000 h
over the 11 seasons; the lowest was in 2008/2009 and the
highest in 2004/2005. The crude injury rate and the 2-year
moving average injury rate are illustrated in figure 1. The
moving average approach indicated an average annual decrease
of 3%, while the log-transformed regression model indicated a
significant annual average decrease of approximately 7%
(R
2
=0.46, b=−0.069, 95% CI −0.125 to −0.012, p=0.023).
No significant differences could be found within the seasons.
Lay-off time
The mean lay-off time in MCL injuries was 23±23
(median=16, Q
1
=8, Q
3
=31) days. The mean lay-off time in
other knee ligament injuries such as anterior cruciate ligament
(ACL), posterior cruciate ligament (PCL) and lateral collateral
ligament (LCL) was 194±75 (median=194, Q
1
=166, Q
3
=228)
days, 52±57 (median=31, Q
1
=12, Q
3
=85) days and 23±26
(median=12, Q
1
=6, Q
3
=27) days, respectively. Sixty per cent
of the MCL injuries affected the dominant leg. There was no
difference in lay-off time between MCL injuries to the dominant
leg compared with the non-dominant leg (median=19, Q
1
=7,
Q
3
=33 vs median=15, Q
1
=8, Q
3
=28, p=0.39).
Circumstances and mechanism
Almost 70% (182/264) of all MCL injuries were due to contact
with another player or an object, which could be compared
with 37% (21/57) among ACL injuries, 70% (7/10) among PCL
injuries and 57% (24/42) among LCL injuries. There was a sig-
nificant association between the distribution of contact/non-
contact injuries and the type of knee ligament injury
(p<0.001). The most common mechanisms of contact injuries
were collision (26%), being tackled (25%) and being blocked
Table 2 Medial collateral ligament injuries of the knee in
professional football
MCL injuries, n (% of total no. of injuries) 346 (4.3)
Reinjuries, n (%) 37 (10.8)
Lay-off days, mean±SD 23±23
Index injury 24±24
Reinjury 18±15
Dominant leg injury 24±22
Non-dominant leg injury 23±26
Contact injury 23±24
Non-contact injury 21±18
Lay-off days, median (Q
1
–Q
3
)16(8–31)
Index injury 18 (8–32)
Reinjury 13 (7–25)
Dominant leg injury 19 (7–33)
Non-dominant leg injury 15 (8–28)
Contact injury 16 (8–29)
Non-contact injury 16 (7–30)
Injury rate* (95% CI) 0.33 (0.29 to 0.36)
Training injury rate 0.14 (0.12 to 0.17)
Match injury rate 1.31 (1.15 to 1.49)
Dominant leg injury rate 0.20 (0.17 to 0.22)
Non-dominant leg injury rate 0.13 (0.11 to 0.15)
Contact injury rate 0.21 (0.18 to 0.24)
Non-contact injury rate 0.10 (0.08 to 0.12)
Injury severity, n (%)
Slight/minimal (0–3 days) 32 (9.2)
Mild (4–7 days) 54 (15.6)
Moderate (8–28 days) 162 (46.8)
Severe (>28 days) 98 (28.3)
Injury burden†(95% CI) 7.6 (7.5 to 7.8)
Lay-off days/player/season, mean±SD 1.8±9.6
*Injury rate expressed as number of injuries/1000 player-hours.
†Injury burden expressed as number of lay-off days/1000 player-hours (injury
rate×mean lay-off).
MCL, medial collateral ligament; Q
1
, 25th percentile; Q
3
, 75th percentile.
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 participate fully in future training
or match play (ie, time-loss injury)
Rehabilitation A player was considered to be injured until team medical
staff allowed full participation in training and availability
for match selection
Reinjury Injury of the same type and at the same site as an index
injury occurring no more than 2 months after a player’s
return to full participation from the index injury
MCL injury A traumatic injury to the superficial MCL, deep MCL and
the posterior oblique ligament leading to a player being
unable to participate fully in training or match play
Slight/minimal injury Injury causing lay-off of 0–3 days from training and
match play
Mild injury Injury causing lay-off of 4–7 days from training and
match play.
Moderate injury Injury causing lay-off of 8–28 days from training and
match play
Severe injury Injury causing lay-off of more than 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
Non-contact injury Injury occurring without contact with another player or
object
Dominant leg Preferred kicking leg
Foul play Violation of the laws of the game according to the match
referee
Injury rate Number of injuries per 1000 player-hours ((Σinjuries/Σ
exposure hours)×1000)
Injury burden Number of lay-off days per 1000 player-hours ((Σlay-off
days/Σexposure hours)×1000)
MCL, medial collateral ligament.
2 of 5 Lundblad M, et al.Br J Sports Med 2013;47:759–762. doi:10.1136/bjsports-2013-092305
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(15%). Thirty-eight per cent of the non-contact injuries, repre-
senting a small fraction of the data, were the consequence of
twisting/turning. No difference in lay-off times between contact
(median=16, Q
1
=8, Q
3
=29) and non-contact (median=16,
Q
1
=7, Q
3
=30) injuries was detected (p=0.74).
Foul play
A higher percentage of foul play injuries were found in MCL
contact injuries compared with other contact injuries during
match play (24% vs 18%, p=0.015).
Variation of injury risk during matches
Approximately 43% (53/123) of the MCL match injuries
occurred during the last 15 min of the first or second half of the
game (see figure 2). This finding is significantly higher than
would be expected (1/3) of the injuries in each quarter of an
hour (p=0.022). No difference was found in the quarterly dis-
tribution between the first and second halves (p=0.76).
Reinjuries
Eleven per cent of all MCL injuries were classified as reinjuries,
which is approximately the same as the reported recurrence rate
for other injuries in the study cohort (12%). There were no dif-
ferences in lay-off time between index injuries (median=18,
Q
1
=8, Q
3
=32) and reinjuries (median=13, Q
1
=7, Q
3
=25;
p=0.20).
Playing position
A significantly higher injury rate was found among outfielders
compared with goalkeepers (0.33 vs 0.17/1 000 h, RR 2.1, 95%
CI 1.3 to 3.2, p=0.001).
DISCUSSION
The principal finding in this study was that MCL injury causes
an average lay-off from professional football for slightly more
than 3 weeks. Another important finding was that MCL injuries
were more frequently caused by contact than non-contact situa-
tions, but, interestingly, lay-off times do not differ significantly
between these two mechanisms. Also, the MCL injury rate
decreased significantly over the 11-year study period.
Injury epidemiology
A professional football team with a typical 25-player squad can
expect around two MCL injuries every season. In spite of a
somewhat fluctuating rate over the seasons, the MCL injury rate
has decreased slightly over time. It is possible to speculate about
whether this is a consequence of (1) less contact between
players during matches and training nowadays, (2) because of
the development of football into a more technically skilled
game or (3) the referees being stricter and more observant of
dangerous contact situations. Another plausible explanation is
that radiological imaging is used more frequently nowadays
compared with the beginning of the study period; there may
have been clinical ‘overdiagnosis’historically. There is, however,
no study showing that the use of radiological imaging reduces
injury rates, shortens lay-off times or reduces injury recurrence.
Figure 1 Seasonal variation in injury
rates for medial collateral ligament
injuries in professional football.
Figure 2 Distribution of medial
collateral ligament injuries during
15 min periods of match play in
professional football.
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Injury circumstances
Almost 70% of all MCL injuries were due to contact with
another player or object. Interestingly, the proportion of
contact-related MCL injuries is thus of approximately the same
percentage as that of non-contact ACL injuries reported in this
study (63%) and in another similar study of elite football.
12
It
therefore appears that the typical injury mechanisms differ
between MCL and ACL injuries, and it is reasonable to believe
that many MCL injuries are the result of a collision or tackle
with physical impact on the outside of the lower part of the
thigh or the upper part of the lower leg. We speculate that, if
the referees are even stricter while judging these situations, the
injury rate may decrease further.
Increased injury rate towards the last 15 minutes
A significant number of MCL match injuries occurred during
the last 15 minutes of the first or second half of the game. It is
possible to speculate that the players are more fatigued towards
the last 15 minutes and therefore fail to react and tackle with
the same precision and speed in their technique as in the first
30 min of the halves. Another possible explanation is that the
players are aware that the halves of the match are about to end
and they perform with greater intensity and more contact in
order to change the outcome of the game in their favour.
MCL injury severity related to lay-off
The ability to predict lay-off is very important for the injured
player, as well as the coaching staff. It appears logical that the
severity of the injury is correlated to the subgrouping of MCL
injuries, if the aim is to predict injury lay-off. In the present study,
16 days was the median value for the lay-off from football after an
MCL injury. Compared with other ligament injuries in the knee,
MCL injury has a rather short lay-off, and can therefore, together
with LCL injury, be regarded as a fairly mild knee ligament injury.
The median lay-off was 194 days for ACL injuries, 31 days for
PCL injuries and 12 days for LCL injuries.
Eleven per cent of all MCL injuries were reinjuries, which is in
line with other injuries in the cohort (12%). There was no signifi-
cant difference in the lay-off time specifically for MCL index
injury and reinjuries. In previous studies, in professional football,
reinjuries have caused longer lay-off than index injuries,
26
but
these studies refer to overall injuries.
Methodological considerations
There are some important methodological issues and limitations
to consider with this study. First, 75% of the MCL injuries were
moderate or severe (ie, >7 lay-off days), and these two groups
could thus be argued to be more relevant to football than slight/
minimal injuries due to their longer lay-off time and greater
recurrence rate. The number of slight/minimal injuries might be
underestimated because, even if the player is seeking medical
attention and has some time loss, it is most probably difficult
for the medical team in many occasions to differentiate
between, for example, a contusion on the medial aspect of the
distal femur and an actual slight MCL sprain if the player com-
pletes a match and is able to train fully within a few days after
the event. Second, the injury form did not include mandatory
information about the clinical or radiological grading of MCL
injury or whether the injury was partial or complete.
Additionally, no information was available on the injury form
about which part of the MCL was damaged (sMCL, dMCL and
POL) or any associated injuries (eg, an MCL injury with a long
lay-off could be associated with occult meniscus or cartilage
lesions). Third, only the main diagnosis is reported on the
injury form, which means that some associated MCL injuries
are missed (eg, in an ACL injury with concomitant MCL injury
only the ACL injury is typically recorded on the general injury
card). Fourth, no systematic information about the treatment
was collected.
What are the new findings?
▸Medial collateral ligament (MCL) injury rates appear to have
decreased during the last decade.
▸MCL injury is more commonly caused by contact than
non-contact situations and more frequently caused by foul
play than non-foul play.
▸There were no differences in return to play between index
MCL injury and reinjury.
How might it impact on clinical practice?
The finding that medial collateral ligament injuries were
more frequently caused by contact and foul play warrants
discussion in the referee sections of the international
governing bodies.
Acknowledgements The authors would like to thank the participating clubs,
medical staff and players. Martin Hägglund is acknowledged for help with data
collection and Christoffer Thomeé for technical assistance.
Contributors ML, MW, JK and JE were responsible for the study concept and
design. JE was responsible for data collection monitoring and co-ordinated the
study. HM was responsible for database management and, together with ML,
conducted all the analyses that were planned and checked with MW, JK and JE. ML
wrote the first draft of the manuscript. All the authors had full access to all data
and contributed to the interpretation of the findings and critical revision of the
manuscript. JE is the study guarantor.
Funding This study was supported by grants from UEFA, the Swedish Centre for
Research in Sports and Praktikertjänst AB.
Competing interests JE is the first vice chairman of the UEFA Medical
Committee.
Patient consent Obtained.
Ethics approval The study design was approved by the UEFA Medical Committee
and the UEFA Football Development Division.
Provenance and peer review Not commissioned; externally reviewed.
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