RossMH, etal. BMJ Open Sport Exerc Med 2018;4:e000430. doi:10.1136/bmjsem-2018-000430
1
Open access Review
Exercise for posterior tibial tendon
dysfunction: a systematic review of
randomised clinical trials and
clinical guidelines
Megan H Ross, Michelle D Smith, Rebecca Mellor, Bill Vicenzino
To cite: RossMH, SmithMD,
MellorR, etal. Exercise
for posterior tibial tendon
dysfunction: a systematic
review of randomised
clinical trials and clinical
guidelines. BMJ Open
Sport & Exercise Medicine
2018;4:e000430. doi:10.1136/
bmjsem-2018-000430
► Additional material is
published online only. To view
please visit the journal online
(http:// dx. doi. org/ 10. 1136/
bmjsem- 2018- 000430).
Accepted 13 August 2018
Department of Physiotherapy,
School of Health and
Rehabilitation Sciences, The
University of Queensland,
Brisbane, Queensland, Australia
Correspondence to
Professor Bill Vicenzino; b.
vicenzino@ uq. edu. au
© Author(s) (or their
employer(s)) 2018. Re-use
permitted under CC BY-NC. No
commercial re-use. See rights
and permissions. Published by
BMJ.
What is already known?
► Posterior tibial tendon dysfunction is a progressive
condition occurring along a continuum from tendon
pain and dysfunction to acquired atfoot deformity.
► Management in the early stages is typically con-
servative, focusing on local strengthening exercises
and arch-supporting devices.
What are the new ndings?
► High-quality clinical trials for the efcacy of exercise
management in posterior tibial tendon dysfunction
are lacking.
► Exercise prescription parameters are poorly reported
in the literature.
► Preliminary evidence suggests exercise is benecial
in reducing pain and disability.
ABSTRACT
Objective To systematically review all randomised
clinical trials to determine the efcacy of local
strengthening exercises compared with other forms of
conservative management for adults with posterior tibial
tendon dysfunction.
Design Systematic review.
Data sources Four electronic databases (Cumulative
Index to Nursing and Allied Health Literature, Cochrane,
Embase and PubMed) were searched up to June 2018.
Eligibility criteria for selecting studies The
study included randomised clinical trials investigating
individuals with posterior tibial tendon dysfunction
where local strengthening was compared with other
forms of conservative management with respect to pain,
function and/or physical impairment outcome measures.
Standardised mean differences (SMDs) were used to
compare change scores between groups and descriptors
of exercise prescription assessed according to the
Template for Intervention Description and Replication and
the Toigo and Boutellier recommendations.
Results 3 studies (n=93) were eligible for inclusion in the
review. Varying strengthening exercises were compared
with stretching and foot orthoses (n=2) or no intervention
(n=1). Moderate effects (SMD 0.6–1.2) were found for
reducing pain and disability with eccentric strengthening
in conjunction with stretching and orthoses compared with
concentric exercises, stretching and orthoses combined,
and stretching and orthoses alone. Evaluation of exercise
prescription parameters demonstrated minimal reporting,
with the only consistent parameters being the number of
sets and repetitions of the exercises, and the duration of
the experimental period.
Conclusion This review demonstrates the paucity of
high-quality research for the conservative management of
posterior tibial tendon dysfunction, and highlights the lack
of exercise prescription parameters reported in clinical
trials.
Trial registration number CRD42017076156.
INTRODUCTION
Posterior tibial tendon dysfunction (PTTD)
is prevalent, with estimates of prevalence
ranging between 3.3% and 10%,
1
but
suspected to be much higher, as the condition
is often not formally diagnosed until the later
stages.
1
PTTD is progressive and disabling,
characterised by impaired mobility,
2
poor
function,
3 4
and often a range of comorbidi-
ties including hypertension and diabetes and
higher body mass index (BMI).
3 5 6
Decisions regarding management vary
according to the stage of the pathology,
7
with reports of surgery predominating, prob-
ably due to the condition more commonly
presenting in later and more severe stages.
8
Surgery aims to correct deformity in the later
stages of the condition (ie, stages III and
IV)
9–11
and, relatively recently, to prevent soft
tissue and joint destructions in earlier stages
(I–II) that do not respond to conservative
management.
12–18
Conservative management is used in earlier
stages (I–II) with a focus on local strength-
ening exercises for the tibialis posterior
musculotendinous unit and use of an orthosis
to brace the foot.
19–21
The level of evidence in
support of this approach is currently unevalu-
ated and is the basis of this systematic review.
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In evaluating the level of evidence, it is important to also
evaluate the quality of reporting of the exercise prescrip-
tion parameters due to the potential influence variations
in these parameters may have on the effectiveness of the
treatment
22
and on clinical practice.
The aims of this systematic review of randomised
clinical trials (RCTs) were to provide estimates of treat-
ment effects of local strengthening exercises compared
with other forms of conservative management for adults
with PTTD on outcomes relating to the international
classification of functioning, disability and health (ICF)
framework (impairments, activity limitations and partici-
pation restrictions), and to evaluate the completeness of
exercise prescription descriptors.
METHODS
This systematic review was performed using a prede-
termined protocol in accordance with the Preferred
Reporting Items for Systematic Reviews and Meta-Anal-
yses statement.
23
It was registered with PROSPERO (trial
registration number CRD42017076156) and is available
at http://www. crd. york. ac. uk/ PROSPERO/ display_
record. php? ID= CRD42017076156.
Search strategy and data sources
To answer the research question about the treatment
effects of local strengthening exercises for PTTD, four
electronic databases (Cumulative Index to Nursing
and Allied Health Literature, Cochrane, Embase and
PubMed) were searched from inception to June 2018 for
full-text papers published in peer-reviewed journals. A
comprehensive search strategy was developed to capture
variations in terminology used in the literature for PTTD
and key conservative interventions (online supplemen-
tary table 1). No further limits were applied to the initial
search strategy. Reference list checks and author searches
were also performed to ensure all relevant literature was
identified.
Eligibility criteria
Eligibility criteria were determined prospectively using
the patient, intervention, comparator and outcome
(PICO) framework.
24
Trials were eligible for inclusion if
they investigated individuals with PTTD or adult-acquired
flatfoot deformity due to PTTD, if they were randomised,
and if local strengthening was compared with other forms
of conservative management with respect to pain, func-
tion and/or physical impairment outcome measures. A
diagnosis of PTTD was required to be made based on a
minimal list of diagnostic criteria,
25
with two or more of
the following: tenderness on palpation of the posterior
tibial tendon, pain and/or swelling along the posterior
tibial tendon, medial foot pain, difficulty and/or pain
with single leg heel raise, and inability to invert the calca-
neus on double leg heel raise. Flatfoot deformity was not
considered as a selection criterion and as such all stages
of PTTD were included.
Trials were excluded if they compared surgical inter-
ventions for PTTD, did not include a comparator group
and combined data for individuals diagnosed with condi-
tions other than PTTD. Reviews, case studies and trials for
paediatric flatfoot, asymptomatic flatfoot, neurological
conditions and rheumatoid arthritis were also excluded.
Study selection
The lead reviewer (MHR) performed the search and
exported all retrieved records into EndNote V.X7
(Thompson Reuters, Carlsbad, California, USA). Dupli-
cates were removed and titles and abstracts were screened
independently by two reviewers (MHR and RM), based on
established eligibility criteria. Full texts were retrieved for
all potentially eligible papers and reviewed for inclusion
and exclusion criteria. Where there were uncertainties, at
least one additional author (MDS or BV) was consulted
to determine final eligibility.
Data extraction
Data extraction for each included trial was completed by
two investigators (MHR and RM) using a predetermined
spreadsheet. Where reference was made to protocol
papers or supplementary materials, these sources were
obtained and used for data extraction. For each trial,
study design, sample size, participant characteristics/
demographics, diagnostic criteria, methods, intervention
details (type, frequency, duration), outcomes, follow-up
and results (means and SDs) for each time point were
extracted.
As reporting of parameters of exercise prescription
is essential for the implementation of research findings
in exercise therapy, these data were also extracted. The
‘Template for Intervention Description and Replication’
(TIDieR) checklist
26
(developed to facilitate reporting
and replication of intervention studies) and the guide-
lines developed by Toigo and Boutellier
27
specifically
for resistance exercise prescription provide a framework
appropriate for the appraisal of exercise prescription in
intervention studies for musculoskeletal conditions.
28
As
such, specific parameters (% repetition maximum, repe-
titions, time under tension and so on) were extracted
to allow for analysis of mechanobiological descriptors
of exercise prescription.
27
Data for the 12-item TIDieR
checklist
26
were also independently extracted by two
reviewers, and the completeness of reporting was eval-
uated by allocating 1 point for complete items (clear,
unambiguous descriptions allowing replication) and 0
for incomplete items (partial or no description) as per
Holden et al.
28
The total scores were calculated for each
checklist and two authors (MDS and BV) verified all
extracted data for accuracy.
Risk of bias
Risk of bias was assessed as recommended by The
Cochrane Collaboration’s tool for assessing risk of
bias in randomised trials.
24
The tool assesses six poten-
tial sources of bias under five domains (selection bias,
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Figure 1 Preferred Reporting Items for Systematic Reviews and Meta-Analyses ow chart for selected trials included for the
systematic review.
performance bias, detection bias, attrition bias and
reporting bias) and considers each as being either ‘low
risk’, ‘high risk’ or ‘unclear risk’ of bias. Two indepen-
dent reviewers (MHR and RM) rated included trials and
the results were collated and examined for discrepancies.
Inter-rater disagreements were discussed and where a
consensus could not be met were taken to a third party
(BV or MDS).
Statistical analyses/data synthesis
Analyses were performed in Review Manager (RevMan)
V.5.3 (Copenhagen: The Nordic Cochrane Centre, The
Cochrane Collaboration). For continuous measures of
pain, function and/or physical impairment, individual
study effect sizes were expressed as standardised mean
differences (SMDs) using means and SDs. The mean
change scores from preintervention to postintervention
were compared between two independent participant
groups (ie, strengthening vs no strengthening; type of
strengthening comparison). Change scores (mean and
SD) for each group were calculated as postscore minus
prescore with within-group correlation assumed to be
0.5
24
and were used to estimate the SD of the mean
change using t-distributions.
The difference between each group was considered
significant where 95% CIs did not contain 0. For pain and
self-reported outcome measures, higher scores indicated
worse outcomes, and as such the inverse of effect size was
reported so that positive effect sizes indicated a benefi-
cial effect for the intervention group. Improvements in
strength and function measures were indicated by higher
scores and positive effect sizes. The strength of the effect
size was interpreted based on Hopkins,
29
as follows: <0.2
trivial effect, 0.2–0.6 small effect, 0.61–1.2 medium effect,
>1.2–2.0 large effect and 2.0–4.0 extremely large effect.
Inter-rater reliability of methodological quality was
calculated in Stata V.13 using the ĸ-statistic (95% CI). The
reliability of the quality ratings between the two assessors
was interpreted as ĸ<0.00 poor agreement, 0.00–0.20
slight agreement, 0.21–0.40 fair agreement, 0.41–0.60
moderate agreement, 0.61–0.80 substantial agreement
and 0.81–1.00 almost perfect agreement.
30
RESULTS
Study selection and design
The electronic database search retrieved 347 studies.
After removing duplicates, 242 titles and abstracts were
screened and 16 potentially eligible full-text trials were
assessed for eligibility (figure 1). Three randomised
controlled trials were included in qualitative and quan-
titative synthesis.
Risk of bias
The inter-rater reliability for the risk of bias assessment
was almost perfect (agreement on 16 of 18 ratings,
ĸ=0.857 (0.47–1)). Risk of bias was variable across the
six items, with insufficient information available to
permit a judgement for two of the three trials on four
items (random sequence generation, allocation conceal-
ment, blinding of participants and personnel, blinding
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Table 1 Included studies
Study
Screened
(n)
Enrolled*
(n) Intervention Comparator Stage
Intervention group Comparator group
n Age† (years)
BMI† (kg/
m
2
)
Female
(%) n Age† (years) BMI† (kg/m
2
) Female (%)
Houck et al
32
88 39 Orthoses+stretching+isotonic
strengthening
Orthoses+stretching II 19 57 (2) 30 (6) 15 (78.9) 17 58 (9) 31 (5) 13 (76.5)
Jeong et al
31
NR 14 Stretching+isotonic ankle
strengthening+balance training
No intervention I or II 7 52.57 (16.13) 22.6 (2.37) 7 (100) 5 53.2 (12.61) 24.02 (3.63) 5 (100)
Kulig et al
33
126 40 Orthoses+stretching+concentric
strengthening
Orthoses+stretching I or II 12 55.3 (16.4) 32 (9.24) 10 (83.3) 12 51.3 (17.2) 28.7 (6.26) 8 (66.7)
Kulig et al
33
126 40 Orthoses+stretching+eccentric
strengthening
Orthoses+stretching I or II 12 49.4 (12.6) 28.5 (7.09) 10 (83.3) 12 51.3 (17.2) 28.7 (6.26) 8 (66.7)
Italics, same comparator group.
*Prerandomisation (includes dropouts).
†Mean (SD).
BMI, body mass index;NR, not reported.
of outcome assessment; online supplementary table 2).
Considering attrition, two trials were deemed to have
low risk of bias as reasons were provided for missing data
(dropouts), which were unrelated to outcomes of the
intervention, and dropouts were balanced across groups.
The third trial had an imbalance of missing data across
groups (2 (29%) vs 0 (0%)) for all outcomes, and due to
the already small sample size (n=14) it is plausible this
was large enough to induce clinically relevant bias. Selec-
tive reporting overall had a high risk of bias. Of the two
trials in which a judgement could be made, there were
outcomes specified in the trial protocol that were omitted
from the final analyses and the manuscript.
Participant characteristics
A total of 93 individuals with PTTD were enrolled across
all trials, with individual sample sizes ranging from 14 to 40
participants (5–19 per group) (table 1). Studies enrolled
participants with a mean age from 52.9
31
to 57.5
32
years
and BMI between 23.3
31
and 30.5
32
kg/m
2
. All studies
had a predominance of women, with the percentage of
women ranging from 77.7%
32 33
to 100%.
31
Two trials
31 33
included individuals with stage I or II PTTD, and one
trial
32
included those with only stage II PTTD.
Selection criteria
In all trials, diagnosis of PTTD was established based on
physical examination findings performed by either phys-
ical therapists or foot and ankle physicians. The number
of essential/compulsory diagnostic criteria ranged
between two and six, with pain along the posterior tibial
tendon, tenderness on palpation of the posterior tibial
tendon, medial foot pain and a correctable flatfoot defor-
mity most frequently used (table 2). Imaging was not used
in any trial to confirm diagnosis or exclude other poten-
tial sources of pain. Only one trial
33
reported a minimum
duration of symptoms and one reported restrictions in
function (able to walk >15 m) and age (>40 years)
32
as
study selection criteria.
Outcome measures
The trials included in this review reported a range of
outcome measures relating to physical impairment,
pain and function (online supplementary table 3).
Two studies
31 33
used a Visual Analogue Scale (VAS) to
measure pain immediately post 5 min walk test (5MWT).
The same two studies
31 33
also reported distance ambu-
lated (m) during the 5MWT. Houck et al
32
reported
tibialis posterior muscle torque with combined plan-
tarflexion and inversion, whereas Jeong et al
31
reported
ankle strength and range of motion in dorsiflexion,
plantarflexion, inversion and eversion. A total of three
patient-reported outcome measures were used, with two
trials
32 33
reporting the Foot Function Index (FFI). The
FFI consists of three domains (pain, disability and activity
limitations) which are summed to provide an overall total
score. Houck et al
32
also used the Short Musculoskeletal
Function Assessment (SMFA), which consists of mobility,
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Table 2 Selection criteria as stated in each study
Trial
Medial
foot/ankle
pain
Pain
PTT
Swelling
of PTT
TOP
PTT
Correctable
flatfoot
deformity
Foot
flattening
Abducted
mid-foot
Duration of
symptoms Imaging Other inclusion criteria
Houck et al
32
NR Either NR √ NR NR NR NR Able to walk >15 m
>40 years of age
Jeong et al
31
√ √ NR √ NR NR NR NR NR NR
Kulig et al
33
√ NR NR √ √ √ √ >3 months NR NR
√, essential eligibility criteria for the study; either, one nding from this group of tests/clinical ndings was required.
NR, not reported; PTT, posterior tibial tendon; TOP, tender on palpation.
dysfunction and bother indexes. Jeong et al
31
reported
the American Orthopaedic Foot and Ankle Society score,
which combines both patient self-report and clinician
physical examination findings into one aggregate score.
34
Reassessment of outcomes varied from 6 weeks
31 32
to 12
weeks.
32 33
Interventions
The exercise intervention protocol varied in each of
the included trials. Local tibialis posterior exercises
were compared with foot orthoses and stretching in two
trials
32 33
; however, the type of exercise (concentric, eccen-
tric or isotonic) varied. Participants in the Kulig et al
33
trial were randomly assigned to either an eccentric or
concentric exercise group (combined with stretching and
orthoses) or a stretching and orthoses-only group (three
groups in total). Houck et al
32
used an isotonic strength-
ening regimen combined with stretching and orthoses
compared with stretching and orthoses only. Participants
in the Jeong et al
31
trial were randomised to receive either
an isotonic ankle strengthening, stretching and balance
programme, or no intervention.
Completeness of reporting
Completeness of intervention reporting based on the
TIDieR checklist is provided in online supplementary table
4. Of the 12 items, Jeong et al
31
provided adequate infor-
mation for 4 items, Houck et al
32
for 11 items and Kulig
et al
33
for all 12 items. Houck et al
32
and Kulig et al
33
both
included sufficient information in regard to adherence
(both the plan for assessment of adherence and reports of
actual adherence).
No trial provided complete reporting of interventions
based on the Toigo and Boutellier
27
exercise prescription
descriptors (table 3). Of the 13 items, Jeong et al
31
provided
adequate information for 5 items, Houck et al
32
for 7 items
and Kulig et al
33
for 11 items. Of the six classical descriptors,
only the number of sets and repetitions of the exercises and
duration of the experimental period over which exercises
were performed were consistently described for all exer-
cises in all trials (table 3). Load magnitude (% repetition
maximum) was only described in one trial.
33
Of the seven
remaining mechanobiological descriptors, the range of
motion and an anatomical definition of the exercise were
described in the methodology of two trials,
32 33
and time
under tension was described in one trial.
33
Main ndings
Physical impairments
Isotonic ankle strengthening, balance and stretching
improved ankle dorsiflexion range at 6 weeks beyond that
of no intervention (SMD (95% CI) 1.71 (0.29 to 3.12))
(figure 2). Plantar flexion inversion torque was not different
at 6 weeks following isotonic tibialis posterior strengthening
exercise combined with stretching and orthoses compared
with stretching and orthoses alone (SMD (95% CI) 0.59
(−0.08 to 1.26)) (figure 2). Isotonic ankle strengthening,
balance and stretching did not improve ankle torque in
any direction at 6 weeks beyond that of no intervention
(figure 2). Local strengthening was not superior to control
comparator for any other physical impairment outcomes at
6 weeks (figure 2).
Neither concentric nor eccentric tibialis posterior
strengthening exercises combined with stretching and
orthoses were significantly different from the control for
the distance covered during the 5MWT at 12 weeks (SMD
(95% CI) 0.51 (−0.34 to 1.36) and 0.25 (−0.57 to 1.07),
respectively),
33
nor were there differences between eccen-
tric and concentric strengthening groups (SMD (95% CI)
−0.39 (−1.22 to 0.44)) (figure 3). There was no difference
between isotonic tibialis posterior strengthening and the
control group for tibialis posterior strength (isometric
combined plantarflexion and inversion) at 12 weeks (SMD
(95% CI) 0.59 (−0.08 to 1.26)) (figure 3).
32
Patient-reported outcomes
Isotonic ankle strengthening, balance and stretching
reduced pain on VAS beyond that of no intervention,
with a large, significant effect size at 6 weeks (SMD (95%
CI) −2.39 (−4.02 to –0.75)) (figure 2).
31
Isotonic strength-
ening moderately reduced scores for the mobility and
dysfunction subscales of the SMFA at 6 weeks (SMD (95%
CI) −1.10 (−1.81 to −0.4) and −0.87 (−1.55 to −0.18),
respectively) (figure 2), but not at 12 weeks (SMD (95%
CI) 0.32 (−0.98 to 0.34) and −0.41 (−1.07 to 0.26), respec-
tively) (figure 3).
32
There were no differences between
local strengthening and control groups for the mean
change on the FFI subscales or total score at 6 weeks
(figure 2) or the SMFA bother subscale at 6 or 12 weeks
(figure 3).
32
Eccentric strengthening combined with stretching
and orthoses reduced the mean scores for FFI-pain,
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Table 3 Exercise descriptors (from Toigo and Boutellier
27
for included trials)
Exercise descriptors
Houck et al
32
Jeong et al
31
Kulig et al
33
BLHR
TheraBand
ADD/INV in PF SLHR
Theraband PF, DF,
INV, EV (weeks 1–6)
Seated HR
(weeks 1–2)
BLHR
(weeks 3–4, 5–6)
SLHR
(weeks 5–6)
ADD in PF
(concentric)
ADD in PF
(eccentric)
1. Load magnitude BW Increasing
resistance
BW
Red → blue → black
Partial BW
BW → loaded
BW 15 RM 15 RM
2. Number of repetitions
10 → 30 10 → 30 10 → 30
20 20 15 15 15 15
3. Number of sets
2 → 3 2 → 3 2 → 3
4 4 3 3 3 3
4. Rest in between sets (s or min) NR NR NR 30 s 30 s 30 s 30 s 1–2 min 1–2 min
5. Number of exercise interventions (per day or week) 2×/day 2×/day 2×/day NR NR NR NR 2×/day 2×/day
6. Duration of experimental period (days or weeks) 12 weeks 12 weeks 12 weeks 6 weeks 6 weeks 6 weeks 6 weeks 12 weeks 12 weeks
7. Fractional/temporal distribution of the contraction per
repetition and duration (s) of one repetition
Isotonic Isotonic Isotonic Isotonic Isotonic Isotonic Isotonic Concentric Eccentric
8. Rest in between repetitions (s or min) NR NR NR NR NR NR NR NR NR
9. Time under tension (s) NR NR NR NR NR NR NR 5 s 5 s
10. Volitional muscular failure No Yes No NR NR NR NR No No
11. Range of motion Full Full Full NR NR NR NR
Neutral →
EOR
EOR →
Neutral
12. Recovery time in between exercise sessions (hours or days) NR NR NR NR NR NR NR NR NR
13. Anatomical denition of the exercise (exercise form)
described
Yes Ye s Ye s No No No No Yes Yes
Total 7 4 11
Items 1–6, classical set of descriptors; items 7–13 (shaded),new set of descriptors.
ADD, adduction; BLHR, bilateral heel raise; BW, body weight; DF, dorsiexion; EV, eversion; EOR, end of range; HR, heel raise; INV, inversion; NR, not reported; PF, plantar exion; RM, repetition maximum; SLHR, single leg
heel raise.
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Figure 2 SMD (95% CI) for outcomes at 6 weeks. 5MWT, 5 min walk test; AOFAS, American Orthopaedic Foot and Ankle
Society; BW, body weight; deg, degree; FFI, Foot Function Index; N/kg, Newtons per kilogram; ROM, range of motion; SMD,
standardised mean difference; SMFA, Short Musculoskeletal Function Assessment; VAS, Visual Analogue Scale.
Figure 3 SMD (95% CI) for outcomes at 12 weeks. 5MWT, 5 min walk test; FFI, Foot Function Index; SMD, standardised
mean differences; SMFA, Short Musculoskeletal Function Assessment; VAS, Visual Analogue Scale.
FFI-disability and FFI-total beyond that of concentric
strengthening, stretching and orthoses combined, and
stretching and orthoses alone at 12 weeks with moderate
effect sizes (SMD (95% CI) −1.1 (−1.97 to −0.23), −0.97
(−1.82 to −0.11) and −0.96 (1.81 to −0.1), respectively;
and SMD (95% CI) 1.1 (−1.97 to −0.23), −0.96 (−1.81
to −0.11) and −0.85 (−1.69 to −0.01), respectively)
(figure 3).
33
Neither concentric nor isotonic tibialis
posterior strengthening combined with stretching and
orthoses was significantly different from stretching and
orthoses alone for the three subscales of the FFI and
FFI-total at 12 weeks (figure 3).
32 33
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DISCUSSION
This systematic review evaluated pain and functional
outcomes following local strengthening exercise in indi-
viduals with PTTD. Two main findings emanate from this
systematic review: the first is the lack of rigorous RCTs
investigating the effects of non-surgical management
on impairments, activity limitations and participation in
adults with PTTD, and the second is that exercise param-
eters are poorly reported.
Detailed reporting of exercise parameters for muscu-
loskeletal interventions trialled in RCTs is essential for
clinical replication and translation of research into prac-
tice. The implications of omitting important exercise
parameters in reporting, however, extend beyond just
clinical replication of exercise prescription. Exercise
parameters such as time under tension, range of motion
and rest or recovery time can be manipulated and are
expected to influence both physiological response to
and efficacy of the exercise prescription,
22 27
meaning
that slight variations in prescription parameters may
have vastly different physiological effects. Factors related
to biophysical response to exercise were not sufficiently
described in the included studies, and strengthening
interventions failed to improve strength-related outcome
measures at both 6 and 12 weeks. Lack of detailed
reporting becomes an important matter when a primary
goal in rehabilitation of tendinopathies is to improve
the load management capacity of the musculotendinous
unit.
35
Current literature implicates appropriate load manage-
ment as the most important component of rehabilitation
for tendinopathies.
35–37
The benefit of therapeutic exer-
cise in the management of lateral epicondylalgia and
Achilles, patellar and rotator cuff tendinopathies has
been established in previous systematic reviews.
38–41
While early literature has focused on eccentric exercise
for tendinopathies,
42–44
more recent approaches with
good efficacy include patient education on load manage-
ment strategies and individualised, progressive loading
exercises.
45
Overall, effect sizes from this systematic
review provide limited evidence to suggest that isotonic
tibialis posterior strengthening, stretching and orthoses
and general isotonic ankle strengthening, balance and
stretching exercises similarly improve pain, mobility
and dysfunction in PTTD in the short term compared
with no strengthening. Considering the specific type of
strengthening protocol, data from this review suggest
that eccentric strengthening may be marginally more
effective than other types of strengthening, with eccen-
tric but not concentric exercise resulting in significant
reductions in self-reported pain, disability and overall
foot function compared with controls at 12 weeks.
The mechanism of effect for improved outcomes in
tendinopathy following strengthening exercise is under-
stood to be related to load. It has been suggested that the
load through the tendon during therapeutic exercises
needs to be sufficiently high enough to elicit physiolog-
ical changes within the tendon. While the relationships
between internal tendon structure and pain and function
are currently unclear,
37
heavy-slow resistance appears to
be beneficial in managing Achilles and patellar tendi-
nopathies.
46
It has been suggested that the physiological
response to therapeutic exercise may be greater with
heavy-slow resistance and eccentric strengthening due to
higher loads applied through the tendon during these
exercises. The device used for strengthening exercise in
the study by Kulig et al
33
allowed for quantification of load
and constant resistance throughout the exercise. Partici-
pants in the eccentric exercise group in their clinical trial
achieved loads 3.3 times higher than those in the concen-
tric group by the end of the 12-week intervention.
33
This
raised the possibility that differences in outcomes were
dependent on load rather than specific contraction
type. Tolerance and ability to perform the exercise with
good form were the criteria for progressing load, which
suggests that participants in the eccentric group were
better able to tolerate higher loads during the exercise
programme, optimising tendon response, and leading to
the reporting of greater improvements in pain, disability
and overall foot function. Physical tests of function
(distance covered during 5MWT), however, were not
different between groups. This suggests that while partic-
ipants felt more confident loading their tendon, physical
capacity of the tendon might not have improved.
Exercise prescription parameters can be manipulated
depending on the desired physiological response to exer-
cise stimulus, for example, to improve skeletal muscle
strength, endurance or power. Each of the three trials
indicated that the intention of the prescribed exercises
was to improve strength. On further examination of the
exercise prescription parameters (table 3) in reference to
the current American College of Sports Medicine (ACSM)
guidelines for muscular strength,
47
some discrepancies
were apparent. Considering load magnitude, the ACSM
guidelines for strength recommend up to 12 repetition
maximum, where Kulig et al
33
prescribed 15, fitting the
ACSM guidelines for muscular endurance.
47
Similarly,
papers prescribed between 15 and 30 repetitions, which
is above the recommendations for inducing strength
adaptations (8–12) and falls into the recommended repe-
titions for improving muscular endurance.
47
Adherence should be considered in calculating
the exercise stimulus (load) actually delivered to the
musculotendinous unit and any strength gains accrued.
Adherence was not reported in Jeong et al,
31
but ranged
between 29% and 126% (average 79%) in Houck et al
32
and 39%–98% (average=68%) in Kulig et al.
33
Consid-
ering this, it is possible the actual load participants
performed was not high enough to elicit adaptations in
skeletal muscle that would subsequently result in clinical
improvements in strength (Houck et al
32
) or physical
tests of function (Kulig et al
33
). Houck et al
32
examined
tibialis posterior force production in plantarflexion and
forefoot adduction at baseline and at 6 and 12 weeks
following isotonic tibialis posterior exercises against the
heaviest TheraBand resistance that could be tolerated,
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in addition to bilateral and unilateral heel raises.
32
The
strengthening group did not exhibit increases in tibialis
posterior strength at 6 or 12 weeks, which suggests that
while the intention of the prescribed exercise programme
was to increase strength, with poor adherence taken into
consideration, actual load may not have been appro-
priate to elicit changes in musculotendinous strength.
It was common among included trials for the inter-
vention protocol to include cointerventions such as
stretching and orthoses, in addition to specific local
strengthening exercises. It is possible that the effect of
the local strengthening intervention was affected by
these cointerventions. As no randomised trial has looked
at local strengthening in isolation (ie, not combined with
stretching/orthoses or balance and stretching exercises),
it is difficult to ascertain to what degree improvements
can be attributed to targeted exercises only. Two trials
that investigated stretching, orthoses and local strength-
ening compared with stretching and orthoses alone
showed similar improvement in pain and function in
all groups. It is possible that orthoses and/or stretching
play a role in the reduction of pain. Future research is
required to investigate strength interventions in isolation
of other treatments to establish its efficacy in the manage-
ment of PTTD.
Interestingly, stretching exercises were included in
all intervention groups across the three included trials.
Both gastrocnemius and soleus stretches were prescribed
for 3–10 repetitions of 30 s duration, 2–4 times per day.
This stretch is performed in maximal dorsiflexion, which
increases the compressive as well as the tensile load on
the posterior tibial tendon posterior to the medial malle-
olus,
48
the combination of which has been found to be
most damaging to the tendon.
49
Load management for
pain relief in tendinopathy rehabilitation is twofold,
incorporating the reduction of both compressive and
tensile loads.
50
So while foot orthoses and activity modi-
fication may aid in altering tensile loads (supporting
the medial longitudinal arch and reducing the torque
required from the tibialis posterior during activities),
accompanying these interventions with static stretches
in full dorsiflexion may be counterproductive to pain
management and rehabilitation.
Pain with palpation, pain on tendon loading and
impaired function are key features in the clinical presen-
tation of tendinopathies.
51–54
Pain and difficulty during
activities that load the medial aspect of the foot and the
posterior tibial tendon, such as the single leg heel raise,
are key clinical features of PTTD. The results from this
systematic review have highlighted that interventions
that aim to modify the load through the tendon and
foot locally (ie, via tibialis posterior strengthening and/
or arch-supporting devices such as foot orthoses) have
limited ability to improve pain and functional outcomes
in PTTD. As such, alternative means of modifying load
to improve clinical outcomes warrant further investiga-
tion. Hip function can affect motion at the foot during
gait,
55–57
and weak hip external rotators and abductors
have been associated with increased femoral internal rota-
tion
58 59
and adduction,
60
increased knee valgus,
59 61
tibial
internal rotation
61–63
and subtalar joint pronation,
62 64
which may impact on tibialis posterior. Increased rear-
foot eversion
65–69
and hip abduction strength
2
deficits
have been demonstrated in PTTD, which suggests that
some proximal changes may be evident in the condition.
Further research investigating proximal muscle function
and kinematics in PTTD would provide further support
for interventions targeting proximal hip motor control
and strength.
Limitations
While this is the first systematic review to investigate the
efficacy of exercise as a treatment for PTTD, there are
several limitations that must be acknowledged. The small
number and variability of interventions and outcomes of
included studies did not allow meta-analysis or pooling
of results. Meta-analysis was prevented due to variability
in selection criteria, methodological quality, interven-
tions and outcome measures assessed among the three
included studies. Small sample sizes of individual studies
can influence the ability to detect true effects. With very
few outcomes replicated between studies, meta-analysis
was prohibited and effect sizes presented in this review
should be interpreted with this in mind. These aspects
of the literature limit the inferences that might be
drawn from the findings. Notwithstanding, this review
is a synthesis of all available evidence from randomised
controlled trials relating to exercise management for
PTTD and highlighted the dearth of evidence on which
to guide management. It must be acknowledged that
studies included in this review related to stage I and/or II
PTTD only. This is an important consideration in terms
of the clinical application of findings and the generalis-
ability of results, given that patient presentation may vary
as the condition progresses.
CONCLUSION
This is the first systematic review on exercise therapy
for PTTD. Based on the limited available literature, it
appears that local strengthening exercises provide some
benefit in PTTD, and eccentric exercises may be superior
for improving pain, disability and self-reported overall
foot function than concentric exercises and foot orthoses
and stretching alone. No recommendations can currently
be made regarding optimal exercise prescription based
on published clinical trials. Clinicians should be guided
by presenting impairments to prescribe exercise, which
holds some promise in managing PTTD.
Contributors All authors contributed equally to this manuscript.
Funding BV is supported by the National Health and Medical Research Council
(NHMRC) Program Grant (#631717), MHR is supported by the University of
Queensland Research Training Program (RTP) Scholarship
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Not commissioned; internally peer reviewed.
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Open access This is an open access article distributed in accordance with the
Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which
permits others to distribute, remix, adapt, build upon this work non-commercially,
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