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Knee Surg Sports Traumatol Arthrosc
DOI 10.1007/s00167-016-4280-1
KNEE
Return to knee‑strenuous sport after anterior cruciate ligament
reconstruction: a report from a rehabilitation outcome registry
of patient characteristics
Eric Hamrin Senorski
1,2
· Kristian Samuelsson
3,4
· Christoffer Thomeé
2
·
Susanne Beischer
1,2
· Jón Karlsson
3,4
· Roland Thomeé
1,2
Received: 19 May 2016 / Accepted: 5 August 2016
© The Author(s) 2016. This article is published with open access at Springerlink.com
involved in knee-strenuous sports, i.e. pre-injury Tegner
of 6 or higher. Return to sport was studied in two different
ways: return to pre-injury Tegner and return to knee-strenu-
ous sport (Tegner 6).
Results Fifty-two patients (33 %), who returned to pre-
injury Tegner, 10 months after surgery, were characterised
by better subjective knee function measured with the knee
injury and osteoarthritis outcome score (p < 0.05), com-
pared with patients who did not. These patients also had
higher perceived self-efficacy of knee function (p < 0.01),
measured with knee self-efficacy scale. Eighty-four
patients (54 %) who returned to knee-strenuous sports,
i.e. Tegner 6 or higher, were characterised by higher goals
for physical activity (p < 0.01) and higher self-efficacy of
future knee function (p < 0.05). Strength measurements
showed that women who returned to sports were stronger
in leg extension than women who did not. No differences
were found in Limb Symmetry Index for knee strength or
jumping ability.
Conclusion Patients who returned to sports after ACL
reconstruction had better subjective knee function and
higher self-efficacy of knee function. Results highlight that
further emphasis should be placed at psychological factors
during rehabilitation of patients after ACLR.
Level of evidence II.
Keywords Anterior cruciate ligament · Reconstruction ·
Registry · Physical therapy modalities · Knee ·
Rehabilitation
Introduction
Far too many patients do not return to sports after an
anterior cruciate ligament (ACL) rupture [9, 41, 44]. One
Abstract
Purpose To characterise patients who returned to knee-
strenuous sports after an anterior cruciate ligament (ACL)
reconstruction.
Methods Data from isotonic tests of muscle function and
patient-reported outcome measures, Tegner activity scale
(Tegner and Lysholm in Clin Orthop Relat Res 198:43–49,
1985), physical activity scale, knee injury and osteoarthri-
tis scale and knee self-efficacy scale were extracted from
a registry. The 157 included patients, 15–30 years of age,
had undergone primary ACL reconstruction and were all
* Eric Hamrin Senorski
eric.hamrin.senorski@gu.se
Kristian Samuelsson
kristian@samuelsson.cc
Christoffer Thomeé
cthomee@gmail.com
Susanne Beischer
susanne.beischer@gmail.com
Jón Karlsson
jon.karlsson@telia.com
Roland Thomeé
roland.thomee@gu.se
1
Unit of Physiotherapy, Department of Health
and Rehabilitation, Institution of Neuroscience
and Physiology, Sahlgrenska Academy, University
of Gothenburg, Box 455, 405 30 Göteborg, Sweden
2
Sportrehab Sports Medicine Clinic, Göteborg, Sweden
3
Department of Orthopaedics, Institution of Clinical Sciences,
Sahlgrenska Academy, University of Gothenburg, Göteborg,
Sweden
4
Department of Orthopaedics, Sahlgrenska University
Hospital, Mölndal, Sweden
Knee Surg Sports Traumatol Arthrosc
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potential long-term concern is that this can result in a too
low sustainable lifelong physical activity. In a comprehen-
sive systematic review, Ardern et al. [3] reported that 81 %
of patients with an ACL reconstruction returned to some
type of sport, while only 55 % returned to competitive
sports participation. Further, more than 50 % of patients
returning to a high level of competition reported that their
performance was reduced compared with their pre-injury
performance [15, 19, 26]. Consequently, it can be argued
that these results could be an indicative of suboptimal treat-
ment or a risk of future impairments and functional limita-
tions for patients after an ACL reconstruction [10, 39, 40,
44]. There can be many reasons, interacting in a complex
manner, why patients do not return to sports. Low self-effi-
cacy beliefs, fear of re-injury and insufficient knee function
are often discussed [26, 27, 41].
A return to physical activity or sports after ACL injury
must be carried out safely, which puts pressure on the
patient’s as well as responsible physician’s and physical
therapist’s judgement [18, 39]. Safety can be defined as
a minimal risk of a re-injury or a subsequent associated
injury in the short term and with decreased risk of osteoar-
thritis in the long term. Return to sports is often seen as a
main outcome when valuing a reconstruction or rehabilita-
tion as successful [25]; however, not returning to sport per
se should not be defined as unsuccessful. The literature has
attempted to present guidelines with objective measure-
ments to facilitate decision-making for the responsible phy-
sician and physical therapist about returning patients safely
to sports in the short term and a sustainable physical activ-
ity in the long term [1, 21, 27, 39]. In spite of this, clini-
cal difficulty still remains when assessing the time at which
patients are ready to return to sports and at what level. In
addition, there is an absence of clear criteria of progression
in the rehabilitation literature, leaving the current practice
of ACL rehabilitation inconsistent [17]. In order to try to
find criteria for a safe, sustainable return to sports, differ-
ent batteries of tests, consisting of various muscle function
tests and patient-reported outcome measures (PROMs),
have been used in the literature [14, 19, 25, 27, 28, 39].
Knowledge of treatment after ACL injury and reconstruc-
tion may be deemed to have increased, but more detailed
characteristics are needed in relation to patients who return
to sports and those who do not, respectively [39]. Popula-
tion-based registry studies provide a unique source of infor-
mation by containing large numbers of patients that are fol-
lowed over a long period of time. The aim of this study was
to utilise a rehabilitation outcome registry to characterise
patients who returned to pre-injury knee-strenuous sports
after ACL reconstruction. The hypothesis was that patients
who return to knee-strenuous sports were characterised by
better knee function, fewer knee-related symptoms and less
impairment during daily activities, sports and recreation, as
well as an enhanced quality of life and higher self-efficacy
of knee function.
Materials and methods
The study was performed as a prospective observational
registry study based on data from an ACL rehabilitation
outcome registry. The registry is based in the western part
of Sweden. It was established in June 2009 and reports on
rehabilitation outcomes for patients with an ACL injury and
ACL reconstruction. The registry consists of two parts: a
patient-reported section and a physiotherapist-reported sec-
tion. Through a website, patients report demographic data
and four validated PROMs: the Tegner activity scale [35],
physical activity scale (PAS) [12], knee injury and osteoar-
thritis outcome score [32] and knee self-efficacy scale [36]
to the database. The physiotherapist enters the results from
tests of the patients’ muscle function. Predefined follow-
ups are set at 10 weeks, 4, 8, 12, 18 and 24 months and
then yearly up to 5 years, followed by every fifth year after
ACL rupture or reconstruction. Participation in the rehabili-
tation outcome registry is voluntary for patients.
Participants
Data were extracted from the rehabilitation registry.
Patients with primary ACL reconstruction from 1 June
2009 to 23 January 2015 were eligible for inclusion
(Fig. 1). Eligible patients had discontinued their rehabilita-
tion 6–18 months after ACL reconstruction, and data from
the follow-up closest in time to the patients’ discharge from
the physiotherapy setting were used. Present definition of
discontinued rehabilitation was based on clearance from
responsible physiotherapist or the patient’s decision to dis-
charge. A further inclusion criterion was a pre-injury self-
reported physical activity level on the Tegner of 6 or higher,
i.e. involvement in a knee-strenuous sport. Patients still
undergoing rehabilitation were excluded as well as patients
younger than 15 years or older than 30 years. Furthermore,
the use of both the Tegner and PAS reinforced that the
patients were regularly involved in sports [6, 39]. All the
patients had completed a structured individualised rehabili-
tation programme at the same sports physiotherapy clinic.
Procedure
Definition of return to physical activity
Return to physical activity was defined in two ways: one,
patients who had returned to their pre-injury level of
Knee Surg Sports Traumatol Arthrosc
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Tegner ± 1 [11, 22, 23] but a minimum of Tegner 6, and
two, patients who had returned to a Tegner of 6 or higher,
i.e. a knee-strenuous sport.
Muscle function
Evaluations of muscle function were performed with a bat-
tery of tests consisting of:
• Two reliable and valid isotonic tests for muscular
strength, to reflect quadriceps and hamstring muscu-
lar power in knee extension and knee flexion [28]. The
strength tests were performed in a knee extension and
knee flexion weight training machine (Precor, Compe-
tition Line, Borås, Sweden). The average power was
recorded through a linear encoder and calculated by
Muscle Lab, a computerised muscle function measur-
ing system (Ergotest Technology, Oslo, Norway). Tests
were performed between 0º and 110° of knee flexion.
• Three reliable and valid single-leg tests for hop perfor-
mance [14]: the vertical jump, the hop for distance and
the side hop.
The results were presented as absolute values accounting
for body weight and with the Limb Symmetry Index (LSI)
[29]. In order for patients to perform the tests of muscle
function, they had to be familiarised with the tests and have
a current absence of pain from their knees during training.
If criteria were not meet, the test leader made an assess-
ment of the patient’s capability of performing the tests of
muscle function.
Patient‑reported outcome measures (PROMs)
Four validated PROMs: Knee injury and osteoarthritis out‑
come score (KOOS) [32], knee self-efficacy scale (K-SES)
[36], Tegner activity scale [35], physical activity scale
(PAS) [36] were used to evaluate factors that have been
shown to be of importance for patients with an ACL injury
[6, 9, 25]. Patients were asked to report their physical activ-
ity on Tegner and PAS for pre-injury, present and future
goals.
Approval has been obtained from the Regional Ethical
Review Board in Gothenburg, Sweden (registration num-
ber: 265-13). The study complies with the revised version
of the Declaration of Helsinki [43]. Procedures are pre-
sented according to the STROBE Statement [42].
Statistical analyses
Statistical analyses were performed using SPSS (version
22, 2013 SPSS Inc., Chicago, IL, USA). Descriptive sta-
tistics, reported as the mean, standard deviation and 95 %
confidence intervals, were used for patient demographics
and outcomes. An independent parametric, t test, and non-
parametric tests, the Mann–Whitney U test, were used for
Number of paents undergone ACL
reconstrucon in the registry
January 23rd 2015
n=388
Paents excluded:
-follow up other than 6-18 months, n=109
-TegnerAcvity Scale <6, n=72
-sll in rehabilitaon, n=32
-age other than 15-30 years, n=18
Paents included in the study,
n=157
(Women n=77, Men n=80)
Fig. 1 Flow chart of inclusion and exclusion criteria
Knee Surg Sports Traumatol Arthrosc
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between-group comparisons for demographic data, tests
of muscle function and outcomes [20]. Alpha was set at
p < 0.05.
Results
Return to pre‑injury Tegner
Fifty-two of the 157 patients (33 %) reported that they
had returned to their pre-injury Tegner ± 1 10 months on
average after the ACL reconstruction. Group demograph-
ics and comparisons for women and men who had and had
not returned to their pre-injury Tegner ± 1 are presented in
Table 1.
No significant difference in the LSI, with values between
90 and 97 %, was found for muscle function between
patients who had returned and for patients who had not
returned to their pre-injury Tegner ± 1. Subjective knee
function as measured with KOOS differed significantly
between groups for all sub-scales: pain (p = 0.038), symp-
toms (p < 0.001), ADL (p = 0.003), sport and recreation
(p < 0.001) and quality of life (p < 0.001; Fig. 2). PROM
scores stratified by returning to pre-injury Tegner ± 1 and
gender are presented in Table 2.
Absolute values for the tests of muscle function and hop
performance, accounting for body weight due to the dif-
ference seen in demographics, showed significantly bet-
ter results for women who had returned, compared with
women who had not returned to their pre-injury Tegner ±
1 for knee extension for injured (mean 3.2 W/kg; 95 % CI
2.7–3.5, respectively, mean 2.6 W/kg; 95 % CI 1.9–2.7,
p = 0.010) and uninjured legs (mean 3.5 W/kg, 95 % CI
2.1–4.1, respectively, mean 2.9 W/kg, 95 % CI 2.3–3.1,
p = 0.014) and side hop for injured (mean 0.7 hops/kg,
95 % CI 0.5–0.9, respectively, mean 0.5 hops/kg, 95 % CI
0.3–0.6, p = 0.012) and uninjured legs (mean 0.8 hops/kg,
95 % CI 0.5–0.9, respectively, mean 0.6 hops/kg, 95 % CI
0.4–0.6, p = 0.004). No differences in absolute values were
seen between men who had and had not returned to their
pre-injury Tegner ± 1 (Table 3).
Return to Tegner 6 or higher
Of the 157 patients, 84 (54 %), 35 women and 49 men,
returned to Tegner 6 or higher. Group demographics by
Table 1 Demographics, comparisons and number of tests by gender for patients that had and had not returned to their pre-injury Tegner activity
scale ± 1
Tegner Tegner activity scale, KOOS knee injury and osteoarthritis outcome score, PAS physical activity scale
* Significant difference between groups, p < 0.05
Demographics Women Men
Returned (n = 23) Not returned (n = 54) p value Returned (n = 29) Not returned (n = 51) p value
Months after surgery 9.9 ± 2.6 10.0 ± 3.5 n.s. 9.9 ± 3.3 10.6 ± 3.4 n.s.
Age
Mean ± SD 20.8 ± 3.0 21.4 ± 3.8 n.s. 23.7 ± 4.5 23.3 ± 4.2 n.s.
Height
Mean ± SD 172 ± 5.8 168 ± 5.3 0.004* 181 ± 7.6 181 ± 5.2 n.s.
Weight
Mean ± SD 67 ± 8.1 62 ± 13.1 n.s. 77 ± 10.5 80 ± 9.2 n.s.
Pre-injury Tegner
Median [range] 8 [6–10] 8 [6–10] n.s. 9 [6–10] 9 [6–10] n.s.
Mean ± SD 7.9 ± 2.3 8.2 ± 1.4 8.1 ± 1.9 8.8 ± 1.0
Pre-injury PAS
Median [range] 4 [3–4] 4 [2–4] n.s. 4 [2–4] 4 [2–4] n.s.
Mean ± SD 3.7 ± 0.5 3.6 ± 0.5 3.7 ± 0.5 3.8 ± 0.9
Knee extension (n)
21 53 29 50
Knee flexion (n)
21 53 29 49
Vertical jump (n)
7 12 8 17
Hop for distance (n)
14 25 18 23
Side hop (n)
14 24 19 22
KOOS (n)
23 54 27 51
Knee Surg Sports Traumatol Arthrosc
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gender are presented in Table 4. Women who had returned
were significantly taller (+3.9 cm) and heavier (+6.6 kg)
than women who had not returned (Table 4).
No difference was found in the LSI, with values between
90 and 96 %, for the tests of muscle function between
patients who had returned and patients who had not
Fig. 2 Knee injury and osteo-
arthritis outcome score subscale
scores with SD for patients who
had and had not returned to
their pre-injury Tegner activity
scale ± 1. *Significant differ-
ence between groups, p < 0.05
0
20
40
60
80
100
Pain Symptom Activities of
Daily Life
Sport and
Recreation
Quality of Life
Knee injruy and Osteoarthritis Outcome Score
Returned
Not returne
d
*
*
*
*
*
Table 2 Patient-reported outcome measure scores by gender for patients that had and had not returned to their pre-injury Tegner activity
scale ± 1
Tegner Tegner activity scale, PAS physical activity scale, K-SES knee self-efficacy scale, KOOS knee injury and osteoarthritis outcome score
* Significant difference between groups, p < 0.05
PROM
Mean ± SD
Median [range]
Women Men
Returned (n = 23) Not returned (n = 54) p value Returned (n = 29) Not returned (n = 51) p value
Tegner present 7.4 ± 2.3 4.4 ± 1.5 <0.001* 7.6 ± 1.9 5.1 ± 1.5 <0.001*
8 [2–10] 4 [2–7] 8 [4–10] 4 [1–7]
Tegner goal 8.1 ± 2.3 7.4 ± 2.4 n.s. 8.2 ± 2.5 8.8 ± 1.1 n.s.
8 [2–10] 8 [5–10] 9 [4–10] 8 [5–10]
PAS present 3.2 ± 1.1 2.7 ± 0.6 <0.001* 3.6 ± 1.3 2.6 ± 0.8 <0.001*
3 [2–4] 3 [1–4] 3 [2–4] 3 [1–4]
PAS goal 3.5 ± 1.1 3.3 ± 1.3 n.s. 3.8 ± 1.4 3.8 ± 0.4 n.s.
4 [2–4] 4 [2–4] 4 [3, 4] 4 [2–4]
K-SES present 6.9 ± 1.4 6.1 ± 1.4 0.005* 7.3 ± 0.8 6.5 ± 1.0 <0.001*
9 [2–10] 8 [3–10] 9 [7–10] 7 [1–10]
K-SES future 7.8 ± 1.9 6.8 ± 2.7 n.s. 8.0 ± 1.4 7.0 ± 1.9 0.026*
9 [1–10] 8 [2–10] 8 [4–10] 7 [2–10]
KOOS pain 80 ± 15 73 ± 16 <0.001* 77 ± 19 69 ± 14 <0.001*
82 [43–100] 71 [36–100] 82 [32–100] 68 [43–100]
KOOS symptoms 91 ± 13 86 ± 11 <0.001* 89 ± 11 84 ± 12 <0.001*
92 [33–100] 89 [61–100] 94 [53–100] 86 [36–100]
KOOS ADL 97 ± 10 94 ± 7 <0.001* 96 ± 9 94 ± 8 <0.001*
100 [47–100] 97 [74–100] 99 [56–100] 97 [68–100]
KOOS sport 80 ± 20 68 ± 22 <0.001* 83 ± 17 66 ± 21 <0.001*
85 [10–100] 70 [15–100] 87 [50–100] 70 [10–100]
KOOS QoL
68 ± 17 55 ± 18
<0.001*
72 ± 16 53 ± 20
<0.001*
63 [13–94] 50 [19–100] 67 [50–100] 56 [13–100]