Lower limb strength following total knee arthroplasty: A

The Knee 21 (2014) 12–20
Contents lists available at ScienceDirect
The Knee
Review
Lower limb strength following total knee arthroplasty: A systematic review
Margaret B. Schache a,b,⁎, Jodie A. McClelland a,c, Kate E. Webster c
a
b
c
Department of Physiotherapy, School of Allied Health, La Trobe University, Melbourne, Australia
Donvale Rehabilitation Hospital, Ramsay Health Care, Melbourne, Australia
Lower Extremity and Gait Studies Program, School of Allied Health, La Trobe University, Melbourne, Australia
a r t i c l e
i n f o
Article history:
Received 8 March 2013
Received in revised form 5 July 2013
Accepted 5 August 2013
Keywords:
Total knee arthroplasty
Muscle
Lower limb
Strength
a b s t r a c t
Background: Total knee arthroplasty (TKA) is commonly performed for end-stage knee osteoarthritis to relieve
pain and improve quality of life. Understanding specific muscle weakness following TKA is required in order to
develop targeted rehabilitation programmes for TKA patients. The aim of this systematic review was to determine whether TKA patients have reduced strength in lower limb muscle groups compared to controls.
Methods: A search of common scientific databases was conducted. A modified published checklist was used to
assess the risk of bias. A meta-analysis was completed for each lower limb muscle group in three separate
post-operative time periods (4–6 months, 1–3 years, and N 3 years). The GRADE approach was used to determine the quality of the evidence.
Results: Fifteen studies met the inclusion criteria for this review. There was low quality evidence for all metaanalyses. The meta-analyses showed that TKA patients had weaker quadriceps than the controls at every postoperative time (pooled effect sizes between −2.81 and −0.53). The meta-analyses of hamstring strength for
patients 1–3 years post-operatively also showed patient weakness (pooled effect size = −1.87) and no significant
difference at N3 years post-operatively (pooled effect size = −0.20).
Conclusion: There was low quality evidence of quadriceps and hamstring weakness following TKA. Further research
is required to determine if other lower limb muscles also display similar muscle weakness. Strategies that specifically target strengthening of these muscle groups may need to be incorporated in rehabilitation to improve outcomes
from TKA. Level of evidence: I.
© 2013 Elsevier B.V. All rights reserved.
Contents
1.
2.
3.
Introduction . . . . . . . . . . . . . . . .
Methods . . . . . . . . . . . . . . . . . .
2.1.
Search strategy . . . . . . . . . . . .
2.2.
Selection criteria . . . . . . . . . . .
2.3.
Outcome measures . . . . . . . . . .
2.4.
Assessment of risk of bias . . . . . . .
2.5.
Data extraction . . . . . . . . . . .
2.6.
Data analysis . . . . . . . . . . . . .
2.7.
Assessment of risk of bias across studies
Results . . . . . . . . . . . . . . . . . . .
3.1.
Selection of studies . . . . . . . . . .
3.2.
Assessment of risk of bias . . . . . . .
3.3.
Study characteristics . . . . . . . . .
3.4.
Outcome measures . . . . . . . . . .
3.4.1.
Quadriceps strength . . . . .
3.4.2.
Hamstring strength . . . . .
3.4.3.
Calf strength . . . . . . . .
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⁎ Corresponding author at: Department of Physiotherapy, La Trobe University, Health Sciences Building 3, Kingsbury Drive, Melbourne, Victoria 3086, Australia. Tel.: +61 3 9841 1257;
fax: +61 3 9842 7276.
E-mail address: schachem@ramsayhealth.com.au (M.B. Schache).
0968-0160/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.knee.2013.08.002
M.B. Schache et al. / The Knee 21 (2014) 12–20
4.
Discussion . . . . . . . . . . . . .
5.
Conclusion . . . . . . . . . . . . .
6.
Conflict of interest statement . . . .
Appendix 1.
Search strategy . . . . . .
Appendix 2.
Modified Downs and Black .
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16
18
18
18
18
20
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18
21
1. Introduction
End-stage knee osteoarthritis (OA) is a significant health problem
worldwide [1,2]. It results in pain and limited participation in many
activities of daily living and functional activities. The most effective
current treatment for end-stage knee OA is total knee arthroplasty
(TKA). TKA is effective in providing pain relief and improving function
in knee OA patients [3] with the assistance from post-operative rehabilitation programmes [4].
Post-operative rehabilitation programmes include gait re-education,
knee range of movement exercises and strengthening exercises.
Emphasis is placed on restoring optimal knee range of movement and
quadriceps strength [5,6]. Hamstring, gluteal and calf strengthening
exercises may also be included. Despite this, muscle weakness and functional limitations persist following TKA [7]. Patients walk more slowly
and have greater difficulty negotiating stairs and performing activities
of daily living than age-matched individuals without knee pathology
[7,8]. These functional limitations are associated with persistent muscle
weakness demonstrated in TKA patients when compared to agematched controls [9]. It is therefore important to have a better understanding of specific and persistent muscle weakness post TKA that will
assist rehabilitation programmes to be more targeted and effective.
The aim of this systematic review was to determine whether TKA
patients have reduced lower limb strength compared to a healthy agematched population, and to identify which lower limb muscle groups
are weaker.
2. Methods
2.1. Search strategy
A search of the following databases was conducted from their inception to March 2012: Medline, Cinahl, Embase, Pedro and Cochrane.
Combinations of the following search terms were used to define the
population: total knee arthroplasty, replacement, prosthesis; and the
outcome of interest: muscle, hip, knee, ankle, lower extremity, quadriceps, hamstring, gluteal, calf, strength, isometric, isokinetic, torque,
force (Appendix 1). Search terms were matched to subject headings in
Medline, Cinahl and Embase.
After deleting duplicate articles from multiple databases, the titles
and abstracts were assessed according to predetermined inclusion and
exclusion criteria. Two examiners assessed the titles and abstracts independently and any discrepancies were resolved with discussion. The full
text article was retrieved for potentially eligible studies and for those
studies where the title and abstract did not provide sufficient information for exclusion. The selection criteria were applied to the full text
article by two examiners. Any disagreements were resolved by discussion. Citation tracking was performed using ISI Web of Knowledge.
The reference lists of included articles were also checked to supplement
electronic searching.
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operative diagnoses included pathologies other than OA and the patients were reported as a single group, only studies where greater
than 80% of the patient population had pre-operative OA were included.
This decision was made because the disease process in other populations such as rheumatoid arthritis and tumour resections have been
shown to affect the strength outcomes after TKA [10,11]. Revision
arthroplasties were excluded because these procedures have been
shown to have strength outcomes that may be different from primary
knee arthroplasty [12,13].
Only studies that recorded maximum strength of isolated lower limb
muscle groups measured on a continuous scale and compared data to a
control group were included. A control group was chosen in preference
to the uninvolved knee because of the high risk of undiagnosed or
developing OA in the contralateral knee, which could have implications
for muscle strength comparisons [14]. Authors were contacted where
necessary to confirm whether multiple manuscripts reported on a common data set.
2.3. Outcome measures
The primary outcome measure was muscle strength of the lower limb
muscle groups. Maximum isometric, isokinetic or concentric muscle
strength produced by isolated lower limb muscle groups was recorded.
2.4. Assessment of risk of bias
A checklist published by Downs and Black [15] was used to assess the
risk of bias of each included study independently by two raters. Discrepancies were resolved by discussion. This checklist was chosen for its
suitability for non-randomised studies and was modified so that it
contained items only relevant to the aim of this review (Appendix 2).
Therefore, items that assessed risk of bias specific to randomised studies,
treatment effects and losses to follow up were removed. The selected
items are listed in Table 1.
2.5. Data extraction
Reporting for the current systematic review followed the Preferred
Reporting Items for Systematic reviews and Meta-analysis (PRISMA)
guidelines [16]. The number of participants, study characteristics, participant characteristics, muscle strength assessment and muscle strength
data were extracted from each study. Where studies presented muscle
strength data in graph form only, an email was sent to the corresponding
author requesting numerical data. If the author could not be contacted,
numerical values were estimated from the published graph(s) [17,18].
The means and standard deviations of data for subgroups such as gender
differences or prosthetic design [7,11,19,20] were collapsed using formulae for the weighted mean and square root of the pooled variance
[21].
2.6. Data analysis
2.2. Selection criteria
Studies were included that investigated patients with a primary TKA
for a diagnosis of OA published in English. In studies where the pre-
Effect sizes were calculated for each comparison of strength between
patients with TKA and controls. These effect sizes were then grouped
according to the type of strength measurement (isometric or isokinetic),
14
M.B. Schache et al. / The Knee 21 (2014) 12–20
Table 1
Assessment of risk of bias.
Downs and Black criteria [15]
Item
no. 1
Item
no. 2
Item
no. 3
Item
no. 5
Item
no. 6
Item
no. 7
Item
no. 10
Item
no. 11
Item
no. 12
Item
no. 25
Item
no. 27
Author
Clear
aim
Outcomes
described
Patients
described
Confounders
described
Main
findings
described
Estimates
of random
probability
Probability
values
reported
Subjects
represent
population
Confounders
comparable
Adjustment
for confounders
Power
calculation
Aquino and Garcez Leme [43]
Bade et al. [3]
Berth et al. [38]
Boonstra et al. [39]
Borden et al. [41]
Ciolac and Greve [40]
Farquhar and Snyder-Mackler [25]
Fuchs et al. [17]
Gapeyeva et al. [18]
Huang et al. [19]
Kim et al. [20]
Levinger et al. [42]
Silva et al. [9]
Walsh et al. [7]
Wigren et al. [11]
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muscle group (quadriceps or hamstrings), and time period postoperatively (4–6 months, 1–3 years or greater than 3 years). A metaanalysis using a random effects model was performed on each group
using StatsDirect statistical software [22]. In studies where there were
multiple assessments of a single population that occurred in the same
category for time period, strength measurement and muscle group, only
one assessment was included to avoid an individual subject being represented twice in the same meta-analysis. For the same reason, where
studies assessed isokinetic strength at multiple speeds the lower speed
was used as slower speeds have been shown to be more reliable [23].
2.7. Assessment of risk of bias across studies
All but five studies [11,18,38–40] used a fixed unit dynamometer to measure muscle
strength. Quadriceps strength was measured by 14 studies of which ten measured isometric
quadriceps strength [3,9,11,18,19,25,38,39,41,42] and five measured isokinetic quadriceps
strength [7,17,19,20,43]. Ten studies measured hamstring strength. Five of these studies
measured isometric hamstring strength [9,11,19,39,41], five measured isokinetic hamstring
strength [7,17,19,20,43] and one study [40] measured concentric hamstring strength. One
study also measured concentric calf strength [40].
3.4. Outcome measures
3.4.1. Quadriceps strength
Meta-analysis of findings was possible for the comparison of isometric quadriceps
strength between patients and controls at all follow-up periods, and for isokinetic strength
at the 1–3 year follow-up period (Fig. 2). For all meta-analyses the quality of evidence was
The Grades of Research, Assessment, Development and Evaluation
(GRADE) approach [24] was used to evaluate the quality of evidence
in each meta-analysis. Each meta-analysis was graded using the following criteria: 1. Inconsistency (downgrade if I2 ≥ 75); 2. Indirectness (no
downgrade applied as all studies measured muscle strength directly);
3. Imprecision (downgrade if upper or lower confidence interval crosses
an effect size of 0.5 in either direction); and 4. Reporting bias (downgrade if modified Downs and Black score average b60%).
Titles and abstracts identified and
screened (n=3732)
Papers excluded after
screening title and abstract
(n=3704)
3. Results
Full text retrieved
(n=28)
3.1. Selection of studies
Fifteen studies were included in the review after an initial yield of 3732 (Fig. 1). Contact with authors confirmed multiple studies initially included in the review contained a
common data set [25–29]. Of these, the study by Farquhar and Snyder-Mackler [25] was
included as it had the largest number of participants. Contact with authors confirmed
that multiple studies also contained another common data set [3,30,31]. For this dataset,
the article by Bade et al. [3] was included as it contained the largest sample that reported
numerical values. One study [32] was excluded because muscle strength was not measured
as an isolated muscle group and six papers [12,33–37] were excluded because muscle
strength was not measured as a maximum force.
3.2. Assessment of risk of bias
Of a possible 11, the number of criteria satisfied by the included studies ranged from
one to 10 (Table 1). In six of these studies factors that could confound strength outcomes
such as age, gender, height, weight or BMI were not reported or were not equal between
the two groups. Power calculations were not reported in 10 of the studies.
3.3. Study characteristics
A summary of the included studies is presented in Table 2. The number of subjects in
each individual study ranged from seven to 183 and there were 906 (495 female, 336
male, 75 not stated) participants in the overall review.
Studies
identified after
searching
reference lists
(n=0)
Papers excluded after
evaluation of full text (n=13)
Reasons:
1. Lower-limb strength not
reported as isolated muscle
groups (n=1)
2. Lower limb strength not
measured as a maximum
strength and recorded as a
numerical value (n=6)
3. Research articles with no
new data (n=6)
Studies
identified from
citations (n=0)
Eligible Studies
(n=15)
Fig. 1. Flow of studies through the selection process.
Table 2
Summary of included studies (n = 15).
Study
TKA subjects
Mean (SD)
Control subjects
Mean (SD)
Age (yrs)
Gender
(M/F)
BMI (kg/m2)
Time post-op
Surgical approach/prosthesis type
Sample size
Age (yrs)
Gender BMI (kg/m2)
(M/F)
17.8 (6) mths,
range = 12–36 mths
6 mths
33 (8) mths
16.7 (5.7) mths
Not stated
25
71.36 (3.24)
0/25
27.40★
Not stated
17
Approach not stated/un-constrained 23
Approach not stated/fixed bearing
31
66.8 (6.5)
63.2
65.4 (8.6)
9/8
8/15
12/19
27.2 (3.5)
26.2
28.4 (3.8)
Approach not stated/PCL retaining
9
68 (6)
4/5
29.76★
Not stated
8
70.4 (5.3)
0/8
28.1 (5.2)
Medial parapatellar/implant not
stated
Subvastus/Genesis-I-prosthesis
25
63.1 (8.4)
10/15
26.8 (4.2)
22
65.5 (8)
11/11
Not stated
10
0/10
9 (16 knees)
64 (range: 52–
75)
68.0 (5.1)
Isokinetic quads & hams
(60°/s, 180°/s)
27 (range: 21–32) Isometric quads (90° flex)
Not
stated
Weight =
59.1 (12.0) kg
30
66 (4)
27.3 (3)
27
65 (11)
10 (15 knees) 62 (7.3)
Not
stated
12/14
3/7
25 (3)
28.9 (5.9)
40
62.8 (1.3)
22/18
25.6 (.69)
96
Not stated
40/46
Not stated
20
71.35 (3.23)
0/20
31.13⁎
24
50
28
65 (9.4)
65.8 (5.6)
65.5 (8.9)
12/12
18/32
11/17
30.7 (4.1)
31
29.7 (5.2)
Borden et al. [41]
8
70 (8)
3/5
29.76⁎
Ciolac and Greve [40]
7
75.3 (3.1)
0/7
32.4 (4.8)
66.4 (8.5)
101/82
30.6 (5.2)
68.1 (8)
8/11
Not stated
Farquhar and
183
Snyder-Mackler [25]
Fuchs et al. [17]
19
10
46 (14) mths,
range = 30–72 mths
38.5 (18.5)
range = 14–66 mths
3 yrs
24.6 (16.7)
range = 4–80 mths
6 mths
Huang et al. [19]
63.0
0/10
(range: 52–74)
36 (50 knees) 68 (6)
Not stated
30.0
(range: 23–38)
Weight = 67.9 7.6 (2.1) yrs
(11.8) kg
range = 6–13 yrs
Kim et al. [20]
45
0/45
27.7 (4.1)
Levinger et al. [42]
Silva et al. [9]
35
67 (7)
16 (25 knees) 65.1 (8.1)
19/16
4/12
30 (4)
31.1 (4.4)
Walsh et al. [7]
29
64.1 (1.5)
16/13
30.3 (1.4)
Wigren et al. [11]
14
68
2/12
Not stated
67.5 (6.5)
14.8 mths
range = 12–18 mths
4 mths
N2 yrs (mean = 2.8,
max = 6 yrs)
12.6 (1.5) mths,
range: 11–17 mths
3 yrs
Medial parapatellar/mixed PCL
retaining and sacrificed
Approach not stated/total condylar,
mobile-bearing, PCL retained and
sacrificed
Medial parapatellar and mini
midvastus/posterior stabilised
Not stated
Approach not stated/posterior
stabilised
Not stated
Medial parapatellar incision/
Modular knee
Isokinetic quads & hams
(60°/s)
Isometric quads (60° flex)
Isometric quads (90° flex)
Isometric quads & hams
(not stated)
Isometric quads & hams
(45° flex)
concentric hams and calf
(not stated)
Isometric quads (75° flex)
Isometric (60° flex) and
isokinetic (120°/s, 180°/s)
quads & hams
Isokinetic quads & hams
(60°/s)
Isometric quads (90° flex)
Isometric quads & hams
(75° flex)
isokinetic quads & hams
(90°/s, 120°/s)
Isometric quads & hams
(not stated)
M.B. Schache et al. / The Knee 21 (2014) 12–20
Sample
size
Aquino and Garcez
Leme [43]
Bade et al. [3]
Berth et al. [38]
Boonstra et al. [39]
Gapeyeva et al. [18]
Strength outcome
measure
(angular velocity or knee
flex angle)
SD, standard deviation; yrs, years; mths, months; M, male F, female; BMI, body mass index (kg/m2); ⁎, BMI calculated from height and weight; quads, quadriceps muscle; hams, hamstring muscle; PCL, posterior cruciate ligament.
15
16
M.B. Schache et al. / The Knee 21 (2014) 12–20
low. At 4–6 months post-operatively, meta-analysis indicated isometric quadriceps weakness (pooled effect size = −2.56; 95% CI −4.43 to −0.68), and a single study reported
reduced isokinetic strength (single effect size = −1.79; 95% CI −2.33 to −1.24). At
1–3 years following TKA, meta-analysis indicated that patients were weaker compared
to controls for isometric (pooled effect size = −0.68; 95% CI −1.02 to −0.34) and
isokinetic contractions (pooled effect size = −2.81; 95% CI −4.72 to −0.90). An additional study that could not be included in the meta-analysis [17] also found quadriceps
strength to be significantly weaker (TKA = 45.07 Nm, Control = 92.05 Nm, p b 0.05)
in TKA patients than controls. Similarly, when patients were more than 3 years following
TKA, meta-analysis indicated reduced isometric strength (pooled effect size = −0.53;
95% CI −1.02 to −0.04) and a single study reported reduced isokinetic strength (single
effect size = −0.54; 95% CI −1.11 to 0.03).
3.4.2. Hamstring strength
Meta-analyses were possible for comparison of hamstrings strength at 1–3 years, and
greater than 3 years post-operative (Fig. 3). The quality of the evidence was low for all
meta-analyses.
A single study compared patients 4–6 months following TKA and reported reduced
isokinetic hamstring strength in the patient group (single effect size = −0.66; 95% CI
−1.13 to −0.18). At 1–3 years following TKA, meta-analyses indicated there was no significant difference between groups for isometric hamstrings contraction (pooled effect
size = −0.76; 95% CI −1.87 to 0.34), but patients had reduced isokinetic strength
(pooled effect size = −1.87; 95% CI −3.65 to −0.08). The additional study that measured isokinetic hamstring strength but could not be included in the meta-analysis ([17]
also found hamstring strength to be significantly weaker (TKA = 62.26 Nm, Control =
132.25 Nm, p b 0.05)) in TKA patients than controls. When patients were more than
Isometric Quadriceps 4–6 months postvop
3 years following TKA, meta-analysis indicated no significant difference in hamstring
strength for either isometric (pooled effect size = −0.23; 95% CI −1.02 to 0.56) or
isokinetic contractions (pooled effect size = −0.20; 95% CI −1.01 to 0.61).
3.4.3. Calf strength
The single study that measured calf strength [40] reported that the patient group had
reduced strength compared to controls at greater than 3 years post-operative. The effect
size was −1.23 (95% CI −2.26 to −0.06).
4. Discussion
This systematic review showed that overall, TKA patients had reduced strength of multiple lower limb muscle groups when compared
to unimpaired control groups, although the evidence for this is low
quality. This muscle weakness was particularly evident for the quadriceps muscle group. The quality of evidence was low in each of the
meta-analyses due to the high heterogeneity of results. There was no
significant difference in hamstring strength between TKA patients and
controls except for isokinetic strength at 4–6 months and 1–3 years
post-operatively. Again there was low quality evidence for these findings due to high heterogeneity particularly in the 1–3 years postoperative period where two studies showed that TKA patients had
weaker hamstrings and one showed that they had stronger hamstrings
Isokinetic Quadriceps 4–6 months post-op
Bade et al. (2010)
Gapeyeva et al. (2007)
Kim et al. (2011)
Levinger et al. (2011)
Total
-8
-7
-6
-5
-4
-3
-2
-1
0
1
-8
-7
-6
Patients weaker
-5
-4
-3
-2
-1
0
1
Patients weaker
I2 (heterogeneity) = 92.7%
Isometric Quadriceps 1–3 years post-op
Farquhar and Snyder-Mackler (2010)
Isokinetic Quadriceps 1–3 years post-op
Aquino and Garcez Leme (2006)
Wigren et al. (1983)
Kim et al. (2011)
Silva et al. (2003)
Boonstra et al. (2008)
Walsh et al. (1998)
Berth et al. (2002)
Total
Total
-8
-7
-6
-5
-4
-3
-2
-1
0
1
-8
-7
-6
-5
-4
-3
-2
-1
0
Patients weaker
Patients weaker
I2 (heterogeneity) = 58.8%
I2 (heterogeneity) = 94.4%
Isometric Quadriceps >3 years post op
1
Isokinetic Quadriceps >3 years post-op
Huang et al. (1996)
Huang et al. (1996)
Borden et al. (1999)
Total
-8
-7
-6
-5
-4
-3
-2
-1
0
Patients weaker
1
-8
-7
-6
-5
-4
-3
-2
Patients weaker
I2 (heterogeneity) = 0%
Fig. 2. Forest plots and meta-analysis of isometric and isokinetic quadriceps strength for each separate post-operative period.
-1
0
1
M.B. Schache et al. / The Knee 21 (2014) 12–20
than controls. Calf strength, measured in one study [40], was also
reduced in the TKA group.
The findings of this systematic review are particularly relevant to
rehabilitation post TKA. The main goals of TKA surgery are to reduce
pain and improve function. Optimizing quadriceps strength post TKA
is considered extremely important for achieving good functional outcomes [44]. There are also many different rehabilitation protocols for
TKA patients that acknowledge the high importance of quadriceps
strengthening [3,5,11,18,45] as well as research to discover more innovative and effective methods to strengthen the quadriceps following
TKA such as neuromuscular electrical stimulation [46–48]. Despite the
emphasis on quadriceps strengthening in most documented protocols,
the patients continue to be weaker than age-matched controls well beyond 3 years post-operatively. The cause of the persistent quadriceps
weakness in TKA patients more than three years post surgery is unclear
from this systematic review. It is possible that current rehabilitation
programmes may be inadequate with respect to type of quadriceps exercises, intensity, timing post-operatively or duration. It is also possible
that the aberrant kinematic patterns adopted by patients following TKA
surgery, in particular the reduced knee flexion angles during loading
phase of gait, reinforce an avoidance of regular quadriceps use [49,50].
17
It would therefore be useful for future research to investigate if patients
who engage in quadriceps strength training at higher levels or for longer
periods of time could achieve quadriceps strength closer to that of the
normal population. In order to maximise our patients' outcome following TKA, rehabilitation programmes must aim to achieve muscle
strength equal to that of healthy individuals.
The strength of lower limb muscle groups other than quadriceps are
also likely to affect functional outcome in patients with TKA. Although
there was a trend towards hamstrings weakness in patients, there
were not enough studies, and there was poor heterogeneity between
studies to draw conclusions based on strong evidence. Calf strength
was investigated by only one study. Weak hamstrings and calf muscles
have implications for the gait patterns of patients with TKA. Reduced
hamstring strength along with reduced quadriceps strength may affect
the patients' balance as co-contraction of the hamstrings and quadriceps is important for knee proprioception and joint stability [51]. The
ankle plantar flexors are critical to both supporting the body and achieving fast speeds of walking, and in people with gait abnormalities it has
been shown that poor ankle plantar flexor function during gait is a
strong predictor of poor mobility outcome [52]. Adequate plantar flexor
function is also important in stair ascent [53]. Therefore, reduced calf
Isokinetic Hamstrings 4 6 months post-op
Kim et al. (2011)
-5
-4
-3
-2
-1
0
1
Patients weaker
Isometric Hamstrings 1 3 years post-op
Isokinetic Hamstrings 1 3 years post-op
Boonstra et al. (2008)
Aquino and Garcez Leme (2006)
Silva et al. (2003)
Kim et al. (2011)
Wigren et al. (1983)
Walsh et al. (1998)
Total
Total
-5
-4
-3
-2
-1
0
1
-5
-4
-3
-2
-1
0
1
Patients weaker
Patients weaker
I2 (heterogeneity) = 92.3%
I2 (heterogeneity) = 95.2%
Isometric Hamstrings >3 years post-op
Isokinetic Hamstrings >3 years post-op
Borden et al. (1999)
Huang et al. (1996)
Huang et al. (1996)
∗Ciolac and Greve 2011 (concentric)
Total
Total
-5
-4
-3
-2
-1
0
1
-5
-4
-3
-2
-1
0
Patients weaker
Patients weaker
I2 (heterogeneity) = 51.4%
I2 (heterogeneity) = 50.1%
1
Fig. 3. Forest plots and meta-analysis of isometric and isokinetic hamstring strength for each separate post-operative period. ⁎Ciolac and Greve (2011) is included in isokinetic
meta-analysis.
18
M.B. Schache et al. / The Knee 21 (2014) 12–20
strength may contribute to difficulty experienced in stair climbing by
many patients with TKA.
There is growing interest in improving hip strength following TKA
and recent evidence suggests hip strength is important in TKA outcomes
[6]. Hinman et al. [54] have demonstrated hip muscle weakness in individuals with medial knee osteoarthritis and it is expected that this deficit is likely to persist following TKA. However, none of the studies
included in this review compared the strength of the hip abductors
with a control group. Piva et al. [6] investigated the contribution of
hip abductor strength to physical function in patients with TKA. They
found that hip abductor weakness had a greater effect than quadriceps
weakness on physical function. Hip strength following TKA and its beneficial effect on function should be investigated in more detail to ensure
rehabilitation programmes address any significant persistent muscle
strength deficits.
The strength of muscles in the contralateral limb was also not investigated by any of the studies in this review. Recent evidence [55] suggests that the contralateral limb strength is the strongest predictor of
outcome following TKA, therefore, it is surprising that little is known
about the strength of the contralateral limb compared to normal. This
is an obvious gap in this area that needs to be addressed to ensure
that rehabilitation programmes are targeting strength impairments
that may be most effective in improving patient outcomes from TKA
surgery.
It is possible that the location of the surgical incision may affect the
strength outcome of lower limb muscles following TKA surgery. However, only five of the included studies provided information about the
incision approach, which was insufficient to warrant analysis of the outcome of strength from these subgroups. Furthermore, there was a variety of TKA prostheses used in the included studies. Whilst it would be of
interest to know whether different prosthesis design characteristics
such as retention or resection of the posterior cruciate ligament lead
to different strength outcomes, there were an insufficient number of
studies with similar prostheses to allow further analysis. To understand
the impact of surgical procedures on strength outcomes following TKA,
further research is needed.
There was large variability in the methodology among the studies.
Nine of the fifteen studies had comparable confounders between their
two groups and nine studies normalized their data for confounding
factors. Knee flexion varied from 45° to 90° in isometric strength testing
and the angular velocity in isokinetic testing varied from 60°/s to 180°/s.
These factors should be considered when interpreting these results
however they did not appear to significantly affect the final outcome.
Despite the fact that these factors may affect the heterogeneity of the results, all of the included studies found similar muscle weaknesses.
Previous research has noted persistent quadriceps deficit, and whilst
this is likely to be the case, this review shows that the overall evidence is
weak and highlights the need for further research in this area. This review has summarised the evidence of persistent quadriceps weakness
post TKA. Further research is warranted to determine if quadriceps
strength can be improved more substantially post TKA. Further research
is required to determine if the hip abductors also display similar muscle
weakness post-TKA. Also, given that hip strengthening reduces symptoms in patients with medial knee osteoarthritis [56] it would be
beneficial to determine the effects of targeted hip strengthening on
functional outcomes following TKA. The calf and contralateral limb
muscle strength should also be assessed. These muscle groups can
then be specifically targeted in rehabilitation in the future.
5. Conclusion
Compared to a control group, muscle weakness exists in the quadriceps and hamstring muscle groups following TKA but the evidence base
is weak. Further research is required to determine if other lower limb
muscles such as the hip abductors, calf and contralateral limb also
display similar muscle weakness following TKA so they can be specifically targeted in rehabilitation.
6. Conflict of interest statement
None of the authors have any personal or financial relationships that
may result in a conflict of interest in the preparation of this manuscript.
Appendix 1. Search strategy
Medline and Embase (inception to March 2012)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
Arthroplasty, Replacement, Knee/
arthroplasty/or arthroplasty, replacement/
Knee Prosthesis/
knee replacement$
total knee replacement$
knee arthroplast$
total knee arthroplast$
knee prosthes$
TKR
TKA
joint replacement$
arthroplast$
1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11 or 12
muscles/or muscle, skeletal/
knee/
Hip/
Ankle/
exp Lower Extremity/
Quadriceps Muscle/
muscle
knee
hip
ankle
lower limb
quadricep$
hamstring$
knee extens$
knee flex$
glute$
hip abduct$
hip extens$
calf
plantarflex$
tibialis anterior
dorsiflex$
14 or 15 or 16 or 17 or 18 or 19 or 20 or 21 or 22 or 23 or 24 or 25 or
26 or 27 or 28 or 29 or 30 or 31 or 32 or 33 or 34 or 35
Muscle Strength/
muscle contraction/or isometric contraction/or isotonic contraction/
torque/
Muscle Weakness/
Muscular Atrophy/
strength
force
isometric
isokinetic
torque
dynamometer
weak$
atrophy
38 or 39 or 40 or 41 or 42 or 43 or 44 or 45 or 46 or 47 or 48 or 49
13 and 36 and 50
M.B. Schache et al. / The Knee 21 (2014) 12–20
Appendix 2. Modified Downs and Black
10. Have the actual probability values been reported (e.g. 0.035 rather
than b 0.05) for the main outcomes except where the probability
value is less than 0.001?
Reporting
1. Is the hypothesis/aim/objective of the study clearly described?
Yes
No
✔
✗
Yes
No
2. Are the main outcomes to be measured clearly described in the
Introduction or Methods section?
If the main outcomes are first mentioned in the Results section, the
question should be answered no. Details of each outcome measure,
no. of trials of strength measurements, position of strength measurements, equipment used must be stated.
✔
✗
Yes
No
3. Are the characteristics of the patients included in the study clearly
described including at least 2 of the following:
- pre-operative diagnosis
- time since surgery
- other disorders affecting muscle strength, e.g.: osteoarthritis in
other joints, rheumatoid arthritis, and neurological conditions?
In cohort studies and trials, inclusion and/or exclusion criteria
should be given. In case-control studies, a case-definition and the
source for controls should be given.
✔
✗
Yes
No
5. Are the distributions of principal confounders in each group of subjects to be compared clearly described? Descriptions of study subjects and control subjects must include more than 2 of the
following to score a tick:
Yes
No
age
gender
height
weight
BMI
All the following criteria attempt to address the representativeness
of the findings of the study and whether they may be generalized to
the population from which the study subjects were derived.
11. Were the subjects asked to participate in the study representative of
the entire population from which they were recruited?
The study must identify the source population for patients and describe how the patients were selected. Patients would be representative if they comprised the entire source population, an unselected
sample of consecutive patients, or a random sample. Random sampling is only feasible where a list of all members of the relevant population exists. Where a study does not report the proportion of the
source population from which the patients are derived, the question
should be answered as unable to determine.
Yes
No
Unable to determine
✔
✗
✗
12. Were the subjects and controls comparable regarding confounding
factors?
The control population should be matched to the study subjects
according to age, gender, height, weight, or BMI. To score a tick, all
study groups must be compared on age, gender and one other factor. Points not awarded if descriptions of subjects and controls only.
✔
✗
Internal validity — confounding (selection bias)
✔
✗
✔
✗
7. Does the study provide estimates of the random variability in the
data for the main outcome?
In non-normally distributed data the inter-quartile range of results
should be reported. In normally distributed data the standard error,
standard deviation or confidence intervals should be reported. If the
distribution of the data is not described, it must be assumed that the
estimates used were appropriate and the question should be answered yes.
Yes
No
✔
✗
External validity
Yes
No
6. Are the main findings of the study clearly described?
Simple outcome data (including denominators and numerators)
should be reported for all major findings so that the reader can
check all major analyses and conclusions. This question does not
cover statistical tests, which are considered below.
Yes
No
19
✓
✗
22. Were study subjects in different intervention groups (trials and cohort studies) or were the cases and controls (case–control studies)
recruited over the same period of time?
For a study that does not specify the time period over which patients were recruited, the question should be answered as unable
to determine.
Yes
No
Unable to determine
✔
✗
✗
25. Was there adequate adjustment for confounding in the analyses
from which the main findings were drawn? i.e.: were results normalized to
a. body weight
b. height
c. or BMI
This question should be answered no for trials if: the main conclusions of the study were based on analyses of treatment rather than
intention to treat; the distribution of known confounders in the
different treatment groups was not described; or the distribution of
known confounders differed between the treatment groups but
was not taken into account in the analyses. In non-randomised
studies if the effect of the main confounders was not investigated or
20
M.B. Schache et al. / The Knee 21 (2014) 12–20
confounding was demonstrated but no adjustment was made in the
final analyses the question should be answered no.
Yes
No
Unable to determine
✓
✗
✗
Power
27. Did the study calculate power to detect a clinically important effect
where the probability value for a difference being due to chance is
less than 5%?
Yes
No
Unable to determine
✔
✗
✗
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