The American Journal of Sports
Medicine
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Return to the Preinjury Level of Competitive Sport After Anterior Cruciate Ligament Reconstruction
Surgery : Two-thirds of Patients Have Not Returned by 12 Months After Surgery
Clare L. Ardern, Kate E. Webster, Nicholas F. Taylor and Julian A. Feller
Am J Sports Med 2011 39: 538 originally published online November 23, 2010
DOI: 10.1177/0363546510384798
The online version of this article can be found at:
http://ajs.sagepub.com/content/39/3/538
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Return to the Preinjury Level of Competitive
Sport After Anterior Cruciate Ligament
Reconstruction Surgery
Two-thirds of Patients Have Not Returned by 12 Months
After Surgery
Clare L. Ardern,*y PT, Kate E. Webster,y PhD, Nicholas F. Taylor,yz PhD, and
Julian A. Feller,y FRACS
Investigation performed at the Musculoskeletal Research Centre, La Trobe University, Bundoora,
Victoria, Australia
Background: An athlete’s desire to return to sport after anterior cruciate ligament (ACL) injury is a major indication for ACL reconstruction surgery. Typical clearance to return is 6 to 12 months postoperatively.
Purpose: To investigate the return-to-sport rate and participation level of a large cohort at 12 months after ACL reconstruction surgery.
Study Design: Case series; Level of evidence, 4.
Methods: Data were analyzed for 503 patients who participated in competitive-level Australian football, basketball, netball, or soccer
after ACL reconstruction surgery using a quadruple-strand hamstring autograft. Inclusion criteria included participation in competitive sport before the ACL injury and clearance from the orthopaedic surgeon to return to sport postoperatively. Patients completed
a self-report questionnaire regarding preoperative and postoperative sports participation and the Cincinnati Sports Activity Scale.
The International Knee Documentation Committee (IKDC) knee evaluation form and hop tests were used to evaluate knee function.
Results: Sixty-seven percent of patients attempted some form of sports activity by 12 months postoperatively; 33% attempted
competitive sport. Of those who did not attempt any sports activity by 12 months, 47% indicated that they were planning to
return. Men were significantly more likely than women to return. Patients who played sports with a seasonal competition, versus
a year-round competition, were significantly more likely to return by 12 months. Patients with normal postoperative knee function
(IKDC category A), versus those with nearly normal function (IKDC category B), were no more likely to return, but patients with
good hop test results (85% limb symmetry index) were more likely to return than patients with poor results (\85%).
Conclusion: People may require a longer postoperative rehabilitation period than that typically advocated to facilitate a successful return to competitive sport after ACL reconstruction surgery. The relationship between postoperative knee function and returnto-sport outcomes at 12 months after surgery was inconclusive.
Keywords: anterior cruciate ligament; anterior cruciate ligament reconstruction; return to sport; knee function; participation
surgery.21 Surgery is performed with the aim of maximizing
the stability and functional capacity of the ACL-deficient
knee,4,18 thereby facilitating return to sport. Current trends
in rehabilitation after ACL reconstruction surgery are for
the provision of programs emphasizing early weightbearing
and the immediate commencement of exercises to restore
knee range of motion and muscle strength. Return to sport
may be permitted as early as 4 to 6 months postoperatively.11
Athletes typically receive clearance to return to sport after
ACL reconstruction surgery around 6 to 12 months postoperatively,2,11 and most are expected to return to sport within
12 months after surgery.14 As such, it is important to have
information regarding the efficacy of ACL reconstruction
surgery in terms of achieving the desired aim of returning
an athlete to sports participation at 12 months.
The anterior cruciate ligament (ACL) is commonly injured
during sports participation, particularly in sports involving
cutting, jumping, and pivoting.7 An athlete’s desire to return
to sport is cited as a major indication for ACL reconstruction
*Address correspondence to Clare L. Ardern, Health Science 3 Building, Musculoskeletal Research Centre, La Trobe University, Bundoora,
3086, Australia (e-mail: c.ardern@latrobe.edu.au).
y
Musculoskeletal Research Centre, La Trobe University, Bundoora,
Victoria, Australia.
z
School of Physiotherapy, La Trobe University, Bundoora, Victoria, Australia.
The authors declared that they had no conflicts of interest in the
authorship or publication of this contribution.
The American Journal of Sports Medicine, Vol. 39, No. 3
DOI: 10.1177/0363546510384798
Ó 2011 The Author(s)
538
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Vol. 39, No. 3, 2011
Return to the Preinjury Level of Competitive Sport
A small number of studies report on short-term returnto-sport outcomes after ACL reconstruction surgery (up to
15 months after surgery).5,9,13,15,16,22 A secondary analysis
of the return-to-sport outcomes of these studies (via proportion meta-analysis; StatsDirect, Altrincham, Cheshire,
United Kingdom)8 demonstrated that 75% of participants
had returned to some form of sports participation at
a mean of 13 months postoperatively. Three of the studies
also evaluated the rate of return to competitive sport at
approximately 12 months postoperatively.5,13,15 These
studies showed that a mean 64% of participants had
returned to competitive sport at follow-up.
Little is known regarding whether the time taken to
return to sport is influenced by the timing of the injury
and subsequent surgery in relation to the seasonal nature
of competitions for some sports and whether there are sex
differences in return-to-sport outcomes. Whereas women
are at greater risk of sustaining an ACL injury,10 it has
not been determined whether they are less likely than
men to return to sport after surgery.
The primary aim of this study was therefore to investigate the return-to-sport rate and participation level in
a large cohort of people at 12 months after ACL reconstruction surgery. Participants were evaluated at 12 months
postoperatively to allow sufficient time for completion of
full rehabilitation and because it was the time when
most were expected to have returned to sport in some
form. The secondary aims of this study were to examine
the return-to-sport intentions of people who had not yet
returned at 12 months after surgery, to evaluate whether
men were more likely than women to have returned to
sport at 12 months after surgery, and to evaluate whether
the seasonal nature of competition in some sports influenced the return-to-sport rate in these sports.
METHOD
Participants
Between May 2003 and December 2008, a total of 1201 primary autologous hamstring ACL reconstructions were performed by the same surgeon. Of these 1201 patients, 1062
(88%) returned for routine surgical review at 12 months. In
sum, 503 patients were participating in competitive level
Australian football, basketball, netball, or soccer before
their ACL injury and were evaluated for this study. Netball is a sport primarily played by women in Australia.
Netball is similar to basketball in court size and ball
used, and goals are scored by throwing the ball through
a ring similar to a backboardless basketball ring. Anterior
cruciate ligament injury is common in netball because of
the predominance of female participants, the cutting, pivoting, and jump-land maneuvers performed, and because
players are not permitted to move when in possession of
the ball.
Surgical Technique and Rehabilitation
All surgical procedures were single-incision arthroscopically assisted ACL reconstructions. All patients received
539
a quadrupled hamstring tendon autograft: 86 patients
received a semitendinosus graft and 417 received a
semitendinosus-gracilis graft. Weightbearing was permitted from the first postoperative day. Emphasis was placed
on the restoration of full knee extension. Quadriceps
strengthening was restricted to closed kinetic chain exercises for the first 3 months postoperatively. Straight-line
running was commenced from 12 weeks, progressing to
sport-specific drills at 16 weeks. Return to full participation in competitive sport was usually permitted at 9
months postoperatively. The criteria for returning to sport
were completion of a full postoperative rehabilitation program, full knee range of motion, a stable knee, functional
quadriceps control, and no effusion. Most patients were
cleared to return to full participation in competitive sport
at 9 months postoperatively, and all participants included
in this study had received clearance from the orthopaedic
surgeon to return to sport postoperatively.
Data Collection
The surgeon aimed to review all patients at 12 months
after surgery. At this review, but before the patient saw
the surgeon, data were collected by a research associate
regarding either postoperative sports participation or
plans to return to sport (for those who had not returned
to competition) and the reasons for not having returned
to sport, in addition to clinical data regarding knee function.
These data were subsequently extracted from the surgical
audit database maintained by the orthopaedic surgeon
and analyzed for the current study. Data analysis was limited to patients who were participating in competitive-level
Australian football, basketball, netball, or soccer before
their ACL injury and who had answered the question
‘‘Have you returned to sports participation following your
ACL reconstruction surgery?’’ Ethics approval was granted
to access data from a surgical audit database for the purposes of this study. All participants had given written consent
for their information to be placed on the database for use in
research.
Outcome Measures
Subjective Evaluation and Return-to-Sport Outcomes.
Patients completed a self-report questionnaire at 12
months after surgery, which was used to collect data
regarding the main sport played before injury, the activity
and level of competition that the patient was involved in
when the injury occurred, and postoperative sports
attempts and plans to return to sport. Specifically, patients
were asked whether they had attempted to play their main
sport after surgery. Responses were coded as not at all,
training and/or modified competition, and full competition. Patients who had not attempted full competition sport
postoperatively were asked to indicate whether they
planned to return to playing their main sport. Return-tosport intentions were coded as yes, unable to play or given
up sport because of my knee, and given up sport or not been
able to return to sport for reasons other than my knee.
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540
Ardern et al
The American Journal of Sports Medicine
Patients also completed the Cincinnati Sports Activity
Scale (SAS) to provide an indication of sports participation
level and knee function. The SAS is scored out of 100, according to the functional demands of the activity on the patient’s
knee and the frequency of participation. A maximum score of
100 is obtained when the patient participates in sports
involving jumping, hard pivoting, and cutting 4 to 7 days
per week. The SAS scores for preinjury and postoperative
sports participation level were collected. Patients were also
asked to rate their operated knee function on a scale from
1 to 100, with 100 being normal. A higher score represents
higher function. Demographic data were also collected.
Clinical Evaluation. The International Knee Documentation Committee (IKDC) knee evaluation form, singlelimb hop for distance, and triple-crossover hop were used
to evaluate knee function and to ensure that patients had
achieved a satisfactory postoperative physical recovery at
12 months. For both hop tests, patients completed 2 trials
on each limb, with the mean score calculated and presented
for the operated limb as a percentage of the nonoperated
limb. Satisfactory knee function was considered to be (1)
an overall classification of normal or nearly normal on the
IKDC knee evaluation form (categories A and B, respectively) and (2) a hop-test limb symmetry index of 85%.1,3
Data Analysis
All data were analyzed with SPSS 17 (SPSS Inc, Chicago,
IL). Descriptive statistics were calculated for all demographic, subjective, and clinical outcome data. The returnto-sport rate was calculated across all sports, as well as
for individual sports to determine whether the overall rate
was influenced by the seasonal nature of competition in
Australian football and soccer. Seasonal sports were defined
as sports played continuously for a discrete period (8 weeks
or greater) and followed by a distinct period where the competition was ceased. Year-round sports were defined as
sports where there was no distinction between the period
of competition and the period of rest from competition.
The return-to-sport rate and return-to-sport intentions
are presented as percentages of the total sample and for
individual sports. Risk ratios and 95% confidence intervals
(CIs) were calculated with the calculator for CIs of relative
risk.6 This was to determine whether relationships existed
between sex and rate of return to competitive sport,
between the clinical assessment of knee function and
return to sport, between the return-to-sport rate for sports
played seasonally and those played throughout the year,
and between sex and return-to-sport intentions. Spitalnic17
recommended that risk ratios be calculated, in preference
to odds ratios, wherever feasible because they present
a more accurate representation of likelihood.
The IKDC form data were dichotomized into good functional outcome (categories A and B) or poor (categories C
and D), as well as normal (category A) or nearly normal
(category B). Hop test data were also dichotomized into
good functional outcome (limb symmetry index of 85%)
or poor (limb symmetry index of \85%). The attemptedreturn-to-sport data were dichotomized into attempted
and not attempted. These data were dichotomized to enable
risk ratios to be calculated. For the purposes of data analysis, Australian football and soccer were classified as seasonal sports, and netball and basketball were classified
as nonseasonal sports. A P value of less than .05 was considered significant for all analyses.
RESULTS
Demographic Data
In sum, 503 patients were eligible for this study. There
were 340 men (68%) and 163 women (32%) who were
reviewed at a mean 53.4 6 4.7 weeks after surgery. The
mean age of all patients at the time of review was 27.2 6
8.4 years. The most common sports participated in before
injury were Australian football (39%) and netball (24%).
Eighty-six percent of patients sustained their ACL injury
during an organized league game, whereas 12% reported
that their injury occurred during participation in recreational sport. Two percent were injured while participating
in an activity other than sport.
Subjective Evaluation
The mean preinjury SAS score was 90.5 6 10.9, whereas
the mean postoperative SAS score was 82.9 6 16.4 (P =
.0001).
Clinical Evaluation
At follow-up, 48% of patients had normal knees (IKDC category A); 45% had nearly normal knees (IKDC category B);
and 7% had abnormal or severely abnormal knees (IKDC C
or D). Eighty-four percent had a hop-test limb symmetry
index of 85% or greater; the mean limb symmetry index
was 93.5% 6 11.2%.
Return to Sport
Sports Participation Attempt. At 12 months postoperatively, 168 patients (33.4%) had attempted full competition, and 169 (33.6%) had attempted training and/or
modified competition (Figure 1). There were 166 patients
(33.0%) who had not attempted to train for or play sport
postoperatively. Men were significantly more likely than
women to have attempted full competition sport by 12
months after their ACL reconstruction surgery (risk ratio,
1.44; 95% CI, 1.01-1.90). Thirty-seven percent of men had
attempted full competition in their preinjury sport, compared with 26% of women. Patients achieving a good functional outcome according to IKDC classification (category
A or B) were no more likely than patients with a poorer
functional outcome (category C or D) to have attempted
full competition sport at 12 months (risk ratio, 1.5; 95%
CI, 0.86-2.50). There was also no difference in return-tosport outcomes between patients with IKDC classification
A and those with IKDC classification B (risk ratio, 1.05;
95% CI, 0.81-1.40). However, patients with a hop-test
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Return to the Preinjury Level of Competitive Sport
541
n = 503
No attempt at
competitive sport
n = 335
Attempted training and/or
modified competition
n = 169
Plan to return to
competitive sport
n = 159
Given up due to
knee function
n = 43
Attempted full
competition sport
n = 168
No attempt at
sports activity
n = 166
Given up for reasons
other than knee
n = 40
No indication of intentions
to return to sport
n = 84
Figure 1. Return-to-sport rate and intentions.
limb symmetry index of 85% were significantly more
likely than patients with a limb symmetry index of \85%
to have attempted full competition sport (risk ratio, 2.5;
95% CI, 1.4-4.4).
Table 1 presents the return-to-sport outcomes for each
sport. Participants who played seasonal sports were significantly more likely than participants who played sports
with year-round competition to have returned to full competition sport by 12 months after surgery (risk ratio, 1.4;
95% CI, 1.1-1.8).
Return-to-Sport Intentions. Of the 335 patients (67% of
the total sample) who had not attempted full competition
by 12 months postoperatively, 159 (47% of the 335) indicated they were planning to return to sport (Figure 1); 40
(12% of the 335) had given up participation for reasons
other than the knee; 43 (13% of the 335) had given up sport
because of knee function; and 84 (25% of the 335) did not
report whether they intended to return to competitive
sport. Men who had not attempted full competition sport
by 12 months postoperatively were no more likely than
women to plan to return to sport (risk ratio, 0.98; 95%
CI, 0.8-1.2). Finally, 63% of men and 64% of women
reported that they were planning to return to sports
participation.
DISCUSSION
The results of this large cohort study showed that by 12
months after ACL reconstruction surgery, only 33% of participants had attempted competitive sport at their preinjury level. When previous studies reporting short-term
return-to-sport outcomes (up to 15 months after surgery)
were analyzed, the rate of return to any form of sport
was 75%,5,9,13,15,16,22 and the return to competitive sport
rate was 64%.5,13,15 The return-to-sport rates reported in
the current study were thus lower—particularly, the
return-to-competitive-sport rate. A possible explanation
for the lower return-to-sport rates in the current study is
the operational definition of return to competitive sport.
The current study specifically evaluated the rate of return
to the same level of competition in the main sport in which
patients participated before their ACL injury. A return to
the preinjury level of sport was thought to represent the
most robust assessment of a successful return-to-sport outcome. Previous studies did not specify whether participants who returned to competitive sport returned to
either their preinjury level of competition or even their
preinjury sport. As a result, these studies may have overestimated the return-to-competitive-sport rate, when compared with the current study. In addition, patients in this
study were permitted to return to full competitive sports
participation from 9 months postoperatively. Other studies
allowed patients to return to sport from 6 months postoperatively. It is possible that the use of 9 months as a target
for the resumption of full sports participation slowed the
rehabilitation and subsequent return to sport, when compared with other studies where patients were permitted
to return to sport at 6 months. Thus, the return-to-sport
rate presented in the current study may be lower when
compared with studies where patients were permitted to
return after 6 months.
Athletes are typically advised that they will require
a break from sport of approximately 6 to 12 months for
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542
Ardern et al
The American Journal of Sports Medicine
TABLE 1
Sports Attempt at 12 Months for Most Commonly Played Sportsa
Seasonal Sports
Overall
n
503
Full competition
n (%)
168 (33.4)
95% CI
29.3-37.5
Training and/or modified competition
n (%)
169 (33.6)
95% CI
29.5-37.7
No attempt
n (%)
166 (33.0)
95% CI
28.9-37.1
Year-round Sports
Australian Rules Football
Soccer
Basketball
Netball
197
102
85
119
83 (42.1)
35.2-49.0
30 (29.4)
20.6-38.3
33 (38.8)
28.5-49.2
22 (18.5)
11.5-25.5
69 (35.0)
28.4-41.7
34 (33.3)
24.2-42.5
24 (28.2)
18.7-37.8
36 (30.3)
22.0-38.5
41 (20.8)
15.1-26.5
37 (36.3)
26.9-45.6
28 (32.9)
23.0-42.9
60 (50.4)
41.4-59.4
a
CI, confidence interval.
full recovery of their knee function after ACL injury and
subsequent surgery. However, if a successful return to
sport is defined as a return to the preinjury sports participation level, the findings of the current study suggest that
many athletes may require a longer period of postoperative
rehabilitation to ensure a successful return to sport. This is
supported by the finding that approximately 50% of the
participants in the current study who had not returned
to competitive sport at follow-up indicated that they
intended to return to sport.
Thing19 suggested that female athletes may take longer
to return to sport than male athletes after an ACL injury.
The current study showed that women were significantly
less likely to have returned to sport at 12 months when
compared with men. However, there were no differences
in women’s intentions to return to sport when compared
with those of the men, among those who had not attempted
sport at follow-up. This is the first study to evaluate
whether the return-to-sport rate after ACL reconstruction
surgery is influenced by sex. These findings are important
because they support Thing’s data and suggest that the
return-to-sport outcomes of female athletes may be lower
than male athletes.
There was a discrepancy between the physical rehabilitation outcomes (eg, knee range of motion, stability, hop
tests) and the return-to-sport rate. More than 85% of participants had normal or nearly normal knees at follow-up,
as measured with the IKDC evaluation form, yet there was
no relationship between IKDC and the return-to-sport
rate. However, patients with a hop-test limb symmetry
index of less than 85% were significantly less likely to
have attempted sport when compared with patients with
a limb symmetry index of 85% or greater. Therefore, the
relationship between function and outcome remains
unclear because with one measure (IKDC) there was no
relationship, yet with another (hop test) there was a
relationship to return-to-sport outcome. Therefore, the
relationship between functional knee status and returnto-sport outcomes requires further investigation.
There is preliminary evidence that psychological factors
may be associated with return to sport after ACL reconstruction surgery. Two studies showed that patients who were up
to 4 years post-ACL reconstruction surgery reported a fear of
reinjury. Patients with a higher fear of reinjury were less
likely to have returned to their preinjury level of sports participation when compared with patients with a lower fear of
reinjury.12,20 Similarly, Webster et al22 showed that athletes
who had returned to their preinjury level of sports participation scored significantly higher on the ACL–Return to Sport
After Injury scale than athletes who had not returned to
their preinjury sports participation level at 12 months after
ACL reconstruction surgery. The scale assesses confidence,
emotions, and risk appraisal, which are aspects of psychological functioning thought to affect the return-to-sport rate
after ACL reconstruction surgery.22 These data, along with
the results of the current study, suggest that further investigation of psychological functioning after ACL reconstruction surgery may be warranted.
The seasonal nature of competition in some sports
appears to have some influence on the return-to-sport
rate. Patients in this study were significantly more likely
to have attempted full competition in seasonal sports at
follow-up when compared with year-round sports. The reasons for this difference are unclear. However, it could be
that seasonal competition gives a more definitive target
date for returning to sport. For example, the athlete may
target the first game of the season for his or her return
to competition. In comparison, in a year-round sport,
with the absence of a distinct season, the motivation for
returning to sport by a specified date may be reduced.
A strength of the current study is its consideration of
return to sport after ACL reconstruction surgery as a primary outcome measure in a large cohort of participants.
In addition, this study evaluated the return-to-sport intentions of participants who had not attempted sport at followup. A major limitation of this study is that it does not
include the results of the 20% of patients who were not followed up at 12 months after surgery. It is possible that
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Vol. 39, No. 3, 2011
Return to the Preinjury Level of Competitive Sport
those who did not attend their follow-up appointment
thought that their progress was satisfactory, had already
returned to sport, and, as such, did not see the need to
attend the follow-up appointment. Conversely, patients
who had not returned to sport and were subsequently
unhappy with their outcome may have chosen not to attend
their follow-up appointment. Also, the current study did not
investigate the reasons people did not return to sport
despite achieving a good physical outcome after surgery
and the reasons why those who indicated that they intended
to return to sport had not returned at follow-up.
10.
CONCLUSION
11.
This study demonstrated that 33% of participants had
attempted to play competitive sport at their preinjury level
and 67% of people had returned to some form of sports participation by 12 months after ACL reconstruction surgery.
Men were more likely than women to return to preinjury
competitive sport at 12 months, and patients who participated in seasonal sports were more likely to return to competitive sport at 12 months than patients who participated
in nonseasonal competition. The relationship between
postoperative knee function and the return-to-sport outcomes at 12 months after surgery was inconclusive. The
results of this study also indicate that the factors that
influence the time taken to return to sport after ACL
reconstruction surgery may be worthy of further investigation and that many people may require a longer postoperative rehabilitation period than that typically advocated to
achieve a successful return to sport.
6.
7.
8.
9.
12.
13.
14.
15.
16.
17.
18.
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