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https://doi.org/10.1177/1759720X211070205
https://doi.org/10.1177/1759720X211070205
Ther Adv Musculoskel Dis
2022, Vol. 14: 1–15
DOI: 10.1177/
1759720X211070205
© The Author(s), 2022.
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Introduction
Mobility is important for quality of life and is a
core indicator of health in aging. Most aged peo-
ple experience mobility impairment slinked to at
least one of the three components of the musculo-
skeletal system (joints, bones, and muscles),
which may affect their ability to move. During
aging, some people suffer of joint discomfort and
pain leading to reduced mobility, affecting their
ability to carry out regular activities. Joint dis-
comfort may result from mechanical stress and
repetitive movement during exercise and physical
activity in aging populations.1 Current medical
treatments aim at decreasing discomfort and
An oleuropein-based dietary supplement
may improve joint functional capacity in
older people with high knee joint pain:
findings from a multicentre-RCT and
post hoc analysis
Marie-Noëlle Horcajada, Maurice Beaumont, Nicolas Sauvageot, Laure Poquet,
Madleen Saboundjian, Berenice Costes, Peter Verdonk, Geoffrey Brands, Jean Brasseur,
Didier Urbin-Choffray, Marc Vandenberghe, Karl Brabants, Kurt De Vlam, Werner Fache,
Bernard Jandrain, Vincent Grek, Michel Malaise and Yves Henrotin
Abstract
Objectives: To investigate a 6-month intervention with an olive leaf extract (OLE) on knee
functionality and biomarkers of bone/cartilage metabolism and inflammation.
Design: This randomized, double-blind, placebo-controlled, multi-centric trial included
124 subjects with knee pain or mobility issues. Subjects received twice a day one capsule of
placebo or 125 mg OLE (Bonolive™, an OLE containing 50 mg of oleuropein) for 6 months. The
co-primary endpoints were Knee injury and Osteoarthritis Outcome Score (KOOS) and serum
Coll2-1NO2. The secondary endpoints were the subscales of the KOOS, knee pain VAS at
rest and at walking, OARSI core set of performance-based tests and multiple inflammatory
and bone or cartilage remodeling serum biomarkers and concentration of oleuropein’s
metabolites in urine.
Results: At 6 months, OLE group was not efficient on global KOOS score, changes of
inflammatory and cartilage remodeling biomarkers compared to placebo. Post hoc analyses
demonstrated a large and significant treatment effect of OLE in a sub-group of subjects with
high walking pain at baseline (p = 0.03). This was observed at 6 months for the global KOOS
score, and each different subscale and for pain at walking (p = 0.02). OLE treatment was well
tolerated.
Conclusion: OLE was not effective on joint discomfort excepted in a sub-group of subjects with
high pain at treatment initiation. As oleuropein is well tolerated, OLE can be used to relieve
knee joint pain and enhance mobility in subjects with articular pain.
Keywords: function, joint pain, nutritional supplement, oleuropein
Received: 5 September 2021; revised manuscript accepted: 13 December 2021.
Correspondence to:
Marie-Noëlle Horcajada
Musculoskeletal Health
Department, Nestle
Research, EPFL Innovation
Park, 1015 Lausanne,
Switzerland
marienoelle.horcajada@
rdls.nestle.com
Yves Henrotin
musculoSKeletal
Innovative research Lab
(mSKIL), The Center
for Interdisciplinary
Research on Medicines
(CIRM), Department
of Motricity Center,
Institute of Pathology,
University of Liège, CHU
Sart-Tilman, 4000 Liège,
Belgium; Artialis SA,
CHU Sart-Tilman, Liège,
Belgium; Department
of Physical Therapy and
Rehabilitation, Princess
Paola Hospital, Vivalia,
Marche-en-Fammenne,
Belgium
yhenrotin@uliege.be
Maurice Beaumont
Nicolas Sauvageot
Nestle Research, Vers-
chez-les-Blanc, Lausanne,
Switzerland
Laure Poquet
Madleen Saboundjian
Nestle Research,
EPFL Innovation Park,
Lausanne, Switzerland
Berenice Costes
Artialis SA, CHU Sart-
Tilman, Liège, Belgium
Peter Verdonk
Antwerpen Orthopedic
Center, Antwerpen,
Belgium
Geoffrey Brands
CHC, Clinique Saint-
Joseph, Liège, Belgium
Jean Brasseur
CHU UCL Namur, Site
Mont-Godinne, Yvoir,
Belgium
1070205TAB0010.1177/1759720X211070205Therapeutic Advances in Musculoskeletal Disease X(X)MN Horcajada, M Beaumont
research-article20212021
Original Research
Therapeutic Advances in Musculoskeletal Disease 14
2 journals.sagepub.com/home/tab
increasing mobility. They generally include non-
steroidal anti-inflammatory drugs (NSAIDs) or
paracetamol to control discomfort and inflamma-
tion. Unfortunately, chronic use of these medica-
tions, particularly in elderly subjects with
comorbidities, can lead to significant adverse
effects, including gastrointestinal bleeding, loss of
kidney function, and/or hepatotoxicity.2–4
Specific nutritional concepts have been developed
to help maintain mobility in aged people by opti-
mizing the structure and function of the musculo-
skeletal system, one of them is based on oral intake
of olive leaf extract (OLE). Olive leaves are the
richest source of olive phenolic compounds, and
OLE is now a popular nutraceutical taken either as
liquid or capsules.5 OLE provides oleuropein, a
secoiridoid, considered as the most prevalent phe-
nolic component in olive leaves and has been shown
to have anti-inflammatory and anti-oxidant effects
potentially interesting for joint health.6 In vitro, ole-
uropein significantly inhibits the interleukin (IL)-
1β-induced production of nitric oxide (NO) and
prostaglandin (PG)E2, expression of cyclooxyge-
nase (COX)-2, inducible Nitric Oxide Synthase
(iNOS), Matrix Metalloprotease (MMP)-1, -13,
and A Disintegrin And Metalloproteinase with
Thrombospondin Motifs (ADAMTS-5) and deg-
radation of aggrecan and collagen-II by human
osteoarthritis (OA) chondrocytes.7 Oleuropein
exerts anti-inflammatory and anti-oxidant effects
via down-regulation of MAPK and NF-κB signal-
ing pathways and induction of Nrf2-linked HO-1
controlling the production of inflammatory media-
tors.7,8 It has recently been demonstrated that ole-
uropein protects against collagen II–induced
arthritis in mice9 and slows down the natural carti-
lage degradation and synovial membrane changes
in Dunkin–Hartley guinea pigs developing sponta-
neous aging-related joint degeneration.10
Benefits of oleuropein have also been reported for
bone health in several in-vivo studies. The con-
sumption of olives,11 olive oil,12 and oleuropein13
prevents the loss of bone mass in experimental
models mimicking osteoporosis that occurs with
aging.14 Ex-vivo studies have demonstrated that
oleuropein inhibits the differentiation of mesen-
chymal stem cells (MSCs) isolated from human
bone marrow into adipocytes15 and enhances dif-
ferentiation into osteoblasts, suggesting it could
prevent age-related bone loss and osteoporosis.16
In this study, we report the effect of an OLE con-
taining 40% oleuropein (OLE) on joint health.
This OLE was previously tested on osteopenic
postmenopausal women at the dose of 250 mg/
day (providing 100 mg oleuropein) for 12 months.
Women taking this OLE showed a reduce loss of
bone mineral density at the lumbar spine and an
increased gain of bone mineral density at the
femur neck compared to those taking placebo.17
We conducted a randomized, double-blinded,
placebo-controlled trial to assess whether supple-
mentation with OLE improves knee pain, dis-
comfort, and loss of mobility in elderly subjects
who reported having mild to moderate functional
knee pain during/after physical activity. In addi-
tion, blood markers reflecting inflammation and
cartilage, or bone metabolism were investigated.
Considering that patients with higher pain inten-
sity are the most responders to antalgic treatment,
we have also conducted a post hoc analysis by
dividing the experimental population into three
groups: low pain, medium and high pain at base-
line. This study is the first ever to have been con-
ducted in full accordance with the International
Council for Harmonization of Technical
Requirements for Pharmaceuticals for Human
use (ICHE6) that examine the impact of ingest-
ing a food supplement composed by OLE on alle-
viating pain (discomfort), function and physical
performance in elderly subjects who reported
having mild to moderate functional knee pain
during/after physical activity.
Population and design
Study design
This study was a randomized, double-blind, pla-
cebo-controlled with two parallel-groups and
multicenter trial in free-living healthy male and
female subjects with moderate knee pain and lost
of mobility. This study included subjects from
Belgium enrolled by 19 health professionals
between June 2016 and April 2018 and was con-
ducted by an independent contract research
organization (CRO, Artialis SA, Liège, Belgium).
The main inclusion criteria were age of 55 years or
over with moderate knee pain evaluated on VAS
(0–100) between 40 and 75 at walking over the
last 24 hours. The most painful knee was consid-
ered. The main exclusion criteria were pregnancy
or lactation, planned knee replacement surgery,
allergy or contraindication to oleuropein, recent
trauma of the knee or rheumatic diseases respon-
sible of the symptomatic knee. Use of any intra-
articular injection in the target knee in the last 3
months, symptomatic slow-acting drugs in OA
Didier Urbin-Choffray
Centre Hospitalier
Régional de la Citadelle,
Liège, Belgium
Marc Vandenberghe
Grand Hôpital de
Charleroi, Charleroi,
Belgium
Karl Brabants
ZNA Middelheim,
Antwerpen, Belgium
Kurt De Vlam
ZNA Jan Palfijn,
Merksem, Belgium
Werner Fache
Linus Pauling Preventie
Centrum, Gent, Belgium
Bernard Jandrain
Clinical Pharmacology
Unit, ATC S.A., Liège,
Belgium
Vincent Grek
2B Clinic, Wavre,
Belgium
Michel Malaise
CHU Sart-Tilman, Liège,
Belgium
MN Horcajada, M Beaumont et al.
journals.sagepub.com/home/tab 3
(SYSADOA) in the last month, oral corticother-
apy in the last 3 months, other dietary supple-
ments used for joint health in the last 3 months
were also exclusion criteria. Subjects enrolled
could have taken paracetamol and/or oral NSAIDs
to manage knee pain. Patients were then asked to
use these rescue medications only when needed
during the trial. Twenty-four hours before a visit,
subjects were asked to stop rescue medication for
the evaluation of clinical parameters by the inves-
tigator. The trial has been conducted in accord-
ance with the European Directive 2001/20/EC
and the Belgian law of May 7, 2004, relating to
experiments on the human person, following
Good Clinical Practices (GCP) guidelines and
according to the ‘Declaration of Helsinki’ pub-
lished by the World Medical Association. The
study protocol was approved by the Central Ethics
Committee of the University Hospital of Liège in
Belgium (namely Comité d’Ethique Hospitalo-
Facultaire Universitaire de Liège), agreement
number: 707. This RCT was also registered on
Clinical trial.gov on March 7, 2017 (https://clini-
caltrials.gov/ct2/show/NCT03072108).
Treatment assignment
The subjects were randomly assigned to one of
the study groups using minimization (dynamic
allocation with p best = 15%): (1) investigational
product one cap twice a day and (2) placebo one
cap twice a day. Randomization was performed
with Medidata Balance and included gender as a
stratification factor. The administration scheme
consisted of one 125-mg capsule of OLE
(Bonolive, consisting of a mixture of polyphenols
derived from olive leaf, standardized for its ole-
uropein content (40%), BioActor BV, Maastricht,
The Netherlands) or placebo twice a day, in the
morning and in the evening at the beginning of
the meal during 6 months. The investigational
product was per capsule 125 mg of OLE contain-
ing 50 mg ± 10 mg of oleuropein plus additives
(microcrystalline cellulose, vegetable magnesium
stearate, silicon dioxide). The placebo was
Maltodextrin Glucidex (IT 19) plus additives
(microcrystalline cellulose, vegetable magnesium
stearate, and silicon dioxide). Compliance with
the study treatments was established by counting
unused study products. A good compliance has
been defined as ⩾85% of product taken through
the entire study. Participants were allowed to
consume habitual foods. Participants were also
allowed to take rescue treatment to manage knee
pain, that is, authorized analgesics except 24 h
before each visit.
Outcome measures
There were two co-primary endpoints, and both
were assessed as the change from baseline to 6
months. They were analyzed by ANCOVA cor-
recting for the measurement at baseline. One end-
point was the Knee injury and Osteoarthritis
Outcome Score (KOOS) using a self-administered
questionnaire. An average of the five subscales was
used. The other endpoint was the serum levels of
Coll2-1NO2, a specific amino acid sequence
located in the triple helicoidal part of type-II col-
lagen and considered as a biomarker of cartilage
degradation.18 sColl2-1NO2 was measured in
diluted serum using an Enzyme Linked Immuno-
Sensitive Assay ELISA method (Artialis SA, Liège,
Belgium). These two endpoints have been consid-
ered hierarchically. A hierarchical testing strategy
assuring a type-1 error rate equal to 2.5% was
used. This consisted in first testing the KOOS
score, and then, in case of statistically significant
results, the biomarker Coll2-1NO2 was analyzed.
The secondary endpoints included each of the five
sub-scales of the KOOS questionnaire, knee pain
on a 100 mm VAS at rest and at walking, the
OARSI core set of performance-based tests (30
second Chair test, timed up and go, stair climb
test), a set of biomarkers evaluating bone (osteoc-
alcin, CTX-1) and cartilage (Coll2-1) metabolism
and inflammation (IL-8, tumor necrosis factor
(TNF)-α, and PGE2,) in serum and concentration
of oleuropein’s metabolites in urine by liquid chro-
matography and identified/quantified by mass
spectrometry coupled to the chromatography
(LC-MS/MS). Serum analyses for biomarkers
have been done by Artialis SA (Liège, Belgium)
using validated immunoassays (ELISA) and
according to written procedures. All adverse events
(AEs) and abnormal laboratory test results were
recorded. The compliance based on pill consump-
tion was computed as the number of caps dis-
pensed minus the number of caps returned. The
percentage of compliance was then assessed by
dividing the consumption by the number of caps
assumed to be taken. For secondary end-points, a
p value < 0.05 was considered as significant.
Statistical analysis
Determination of the sample size. The effects to
be estimated were the treatment difference
Therapeutic Advances in Musculoskeletal Disease 14
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between OLE and placebo in KOOS at 6 months
and the treatment difference between OLE and
placebo in Coll2-1NO2 at 6 months. In order to
show in a two-group parallel design a difference
of 10 score point in KOOS pain subscale with a
standard deviation of 16 score points as statisti-
cally significant at an alpha level of 5% and a
power of 90%, 55 subjects should be analyzed. In
order to show a difference of 5.1 nM in Coll2-
1NO2 with a standard deviation of 8.73 nM as
statistically significant at an alpha level of 5% and
a power of 80%, 47 subjects needed to be ana-
lyzed. So, 55 subjects were needed by group, these
were 110 in total. Considering a 15% drop-out
rate, a maximal number of 126 subjects were
required.
Statistical analyses for primary endpoints. For
each endpoint, the descriptive statistics presented
were number of subjects (n), mean, standard
deviation (SD), standard error of the mean
(SEM), min and max, lower quartile (Q1),
median and upper quartile (Q3) as well as the p
value of Shapiro–Wilk. A linear mixed model was
used with baseline value, visit and treatment as
covariates. Within-subject correlations were
described through a covariance pattern model
and specified with a covariance structure. Three
structures were tested, that is, compound symme-
try, unstructured, and time-series-type, and cho-
sen according to the Akaike information criterion
(AIC).
Statistical analyses for secondary endpoints. The
same ANCOVA model correcting for baseline
value as mentioned in the primary analysis was
used to analyze secondary endpoints. If the statis-
tical assumptions of the ANCOVA model were
not fulfilled, a log transformation was used to
meet them. In this case, n, geometric mean (geo.
mean), the lower and upper bounds defined as
[geom. Mean/geom. SD, geom. Mean * geom
SD], min and max were presented. If a log trans-
formation did not help, it was planned to use the
non-parametric Wilcoxon rank-sum test which
was not necessary in this study.
For biomarkers with a percentage of measure-
ments below limit of detection (LOD) or lower
limit of detection (LLOQ) which was superior to
30%, a comparison of the proportion of subjects
with detectable versus non-detectable values
between the two treatment groups was performed
at each visit. Detectable values were defined as
values measured as well as values below LLOQ,
whereas non-detectable values were defined as
values below LOD. For biomarkers with a per-
centage of measurements below LOD or LLOQ
which is inferior to 30%, linear mixed models
were performed. In order to do it, biomarkers
have to be considered as continuous variables.
Therefore, measurements below LOD were
replaced by 0. Regarding measurements below
LLOQ, if a measurement was still provided, this
measurement was used. Otherwise, measure-
ments below LLOQ were replaced by LLOQ/2.
Post hoc analysis. We also performed a post hoc
analysis based on the tertiles of VAS score at walk-
ing measured at baseline. The group of subjects
having a low VAS score at baseline included sub-
jects with a VAS score inferior to the first tertile.
The group of subjects having a medium VAS
score at baseline included subjects with a VAS sta-
blecore superior to the first tertile and inferior to
the second tertile. Finally, the groups of subjects
having a high VAS score at baseline included sub-
jects with a VAS score superior to the second ter-
tile. Only data on both extreme tertiles will be
presented. Same linear mixed models than those
used for main analyses were performed to assess
treatment difference between sub-groups. These
sub-group analyses were performed on primary
endpoints as well as the five different subscales of
the KOOS score.
Results
Population
Out of the 138 subjects screened, 126 were rand-
omized and considered eligible for the Intention-
To-Treat (ITT) analysis and 118 for the full
analysis set (FAS) analysis. The per-protocol set
included 85 subjects of the FAS who also com-
pleted the study and did not have any major pro-
tocol deviation. Among the FAS population, 59
received Bonolive and 59 received placebo
(Figure 1). The cumulative time distribution of
withdrawals was similar in the two groups with-
out significant differences in the reasons for with-
drawals. At baseline, participants in each group
were well-matched (Table 1). Female and male
were equally distributed between the two groups,
with 49.1% and 52.5% of male in the placebo
and OLE groups, respectively. About 52% and
54% of the subjects were overweigth (25 < BMI
< 29.9 kg/m2) among placebo and OLE groups,
respectively. No significant differences were
observed between the two treatment groups
MN Horcajada, M Beaumont et al.
journals.sagepub.com/home/tab 5
according to demographic characteristics and
BMI. The global KOOS score was similar in both
groups (mean ± SEM: placebo 54.1 (2.5) vs OLE
49.8 (2.0), p = 0.22). The KOOS pain subscore
was higher in the placebo group as compared with
the OLE group at baseline (p = 0.025; Table 1))
sColl2-1NO2 levels were also comparable
(mean ± SEM: placebo 2694 (181) pg/mL vs
OLE 2638 (249) pg/mL, p = 0.35).
Primary outcomes
Both primary endpoints increased significantly
across visits (Figure 2). Global KOOS score
tended to be higher in the OLE group at each
time point but the difference with the placebo
group was not significant (Figure 2(a)). The dif-
ference of the least squares (LS) mean also tended
to increase with time suggesting that the magni-
tude of OLE effect enhanced with time (Table 2).
At each time point, Coll2-1NO2, a specific
marker of oxidative-related cartilage degradation,
tended to be higher in OLE group compared to
placebo (Figure 2(b)), but no significant differ-
ence between groups was reached (Table 3).
These observations were similar in the FAS and
PP population.
Secondary outcomes
The KOOS subscores (pain, other symptoms,
function in daily living (ADL), function in sport
and recreation (Sport/Rec), and knee-related
quality of life (QOL)) increased during the first 3
months and then remained stable until month 6
in both PP and FAS population (Supplemental
Appendix 1). No difference between treatment
groups was observed using the FAS and PP popu-
lation. Compared to placebo, OLE did not sig-
nificantly improve the KOOS subscores (Table 2)
(Supplemental Appendix 1). The pain intensity
at rest decreased with time in both FAS and PP
population (Supplemental Appendix 2), but no
difference between treatment groups was observed
(Table 2). Similarly, pain during walking
decreased with time in both treatment group
124 subjects included
ITT OLE
N=62 randomized
FAS
N=59
PP
N=45 completedday 180
ITT Placebo
N=62 randomized
FAS
N=59
PP
N=40 completedat day180
N= 13 disconnued
Adverse events: 3
Lostto follow-up :2
Withdrew with explanaon:7
Withdrew withoutexplanaon:1
N= 10 disconnued
Adverse events: 3
Lost tofollow-up:2
Withdrew with explanaon:3
Withdrew withoutexplannaon:2
126 subjects signed
informed consent
2 subjects were
screening failure
Figure 1. Disposition of subjects.
FAS, full analysis set; ITT, intention to treat; N, number; PP, per-protocol.
Therapeutic Advances in Musculoskeletal Disease 14
6 journals.sagepub.com/home/tab
Table 1. Demographic and baseline characteristics.
Placebo (N = 59) OLE (N = 59) Total (N = 118) p values
Gender n/n miss 59/0 59/0 118/0 0.71
Male, n (%) 29 (49.1%) 31 (52.5%) 60 (50.8%)
Female, n (%) 30 (50.9%) 28 (47.5%) 58 (49.1%)
Ethnicity n/n miss 59/0 59/0 118/0 0.19
Asian, n (%) 1 (1.7%) 0 (0%) 1 (0.8%)
African, n (%) 2 (3.4%) 1 (1.7%) 3 (2.5%)
Caucasian, n (%) 56 (94.9%) 58 (98.3%) 114 (96.6%)
Age (years) n/n miss 59/0 59/0 118/0 0.23
Mean (SEM) 64.3 (0.89) 62.8 (0.85) 63.6 (0.61)
Median 64 62 63
Q1, Q3 59, 69 57, 67 57, 68
Min, Max 55, 82 53, 79 53, 82
BMI (kg/m2)n/n miss 59/0 59/0 118/0 0.55
Mean (SEM) 25.6 (0.46) 25.3 (0.32) 25.4 (0.28)
Median 25.5 25.2 25.4
Q1, Q3 23.5, 28.5 23.9, 27.1 23.7, 27.7
Min, Max 18.5, 35.2 19.2, 29.9 18.5, 35.2
Overall KOOS n/n miss 56/3 59/0 115/3 0.22
Mean (SEM) 54.1 (2.5) 49.8 (2.0) 51.9 (1.6)
Median 52.8 51.3 52.3
Q1, Q3 41.9, 70.2 39.7, 60.6 40.6, 65.0
Min, Max 11.8, 87.8 15.2, 87.6 11.8, 87.8
Coll2-1 NO2 (pg/mL) n/n miss 57/2 59/0 116/2 0.35
Mean (SEM) 2694 (181) 2638 (249) 2666 (154)
Median 2309 2068 2136
Q1, Q3 1686, 3421 1517, 2963 1614, 3345
Min, Max 932, 6466 253, 10304 253, 10304
KOOS pain n/n miss 59/0 59/0 118/0 0.025
Mean (SEM) 61.0 (2.5) 52.2 (2.4) 56.6 (1.8)
Median 58.3 52.8 58.3
Q1, Q3 47.2, 75.0 38.9, 66.7 41.7, 69.4
Min, Max 16.7, 94.4 0.0, 86.1 0.0, 94.4
(Continued)
MN Horcajada, M Beaumont et al.
journals.sagepub.com/home/tab 7
Placebo (N = 59) OLE (N = 59) Total (N = 118) p values
KOOS Adl n/n miss 59/0 59/0 118/0 0.44
Mean (SEM) 63.0 (2.9) 60.1 (2.5) 61.6 (1.9)
Median 63.2 63.2 63.2
Q1, Q3 44.1, 82.4 44.1, 76.5 44.1, 76.5
Min, Max 7.4, 98.5 14.7, 97.1 7.4, 98.5
KOOS symptom n/n miss 59/0 59/0 118/0 0.5
Mean (SEM) 65.9 (2.5) 63.6 (2.2) 64.7 (1.7)
Median 64.3 67.9 67.9
Q1, Q3 50.0, 82.1 50.0, 78.6 50.0, 78.6
Min, Max 28.6, 100.0 28.6, 89.3 28.6, 100.0
KOOS sport n/n miss 56/3 59/0 115/3 0.27
Mean (SEM) 36.4 (3.4) 30.5 (2.6) 33.4 (2.1)
Median 30 30 30
Q1, Q3 12.5, 60.0 15.0, 40.0 15.0, 50.0
Min, Max 0.0, 90.0 0.0, 95.0 0.0, 95.0
KOOS Qol n/n miss 59/0 59/0 118/0 0.88
Mean (SEM) 43.8 (2.9) 42.6 (2.2) 43.2 (1.8)
Median 37.5 43.8 43.8
Q1, Q3 31.3, 62.5 31.3, 50.0 31.3, 56.3
Min, Max 0.0, 87.5 6.3, 75.0 0.0, 87.5
Knee pain VAS
score at rest
n/n miss 59/0 59/0 118/0 0.76
Mean (SEM) 45.2 (2) 45.4 (2.4) 45.3 (1.5)
Median 45 47 45
Q1, Q3 40, 58 40, 60 40, 59
Min, Max 10, 73 0, 74 0, 74
Knee pain VAS
score at walking
n/n miss 59/0 59/0 118/0 0.82
Mean (SEM) 58.1 (1.4) 57.3 (1.4) 57.7 (1)
Median 59 59 59
Q1, Q3 50, 65 48, 70 49, 66
Min, Max 40, 100 32, 75 32, 100
BMI, body mass index; KOOS, Knee injury and Osteoarthritis Outcome Score; OLE, olive leaf extract; SEM, standard error of
the mean; VAS, Visual analog scale.
Table 1. (Continued)
Therapeutic Advances in Musculoskeletal Disease 14
8 journals.sagepub.com/home/tab
(Supplemental Appendix 2) with no differences
between treatment groups.
Other clinical and performance parameters were
not significantly modified by OLE (Table 2). The
30s chair score increased with time in both group
in the FAS and PP population, while the time-up
and go scores remained stable overtime and stair
climb time decreased (Supplemental Appendix 3).
The biomarker Coll2-1NO2 and Coll2-1
increased significantly between baseline and
month 6, while IL-8 and PGE2 levels decreased
and CTX-1, osteocalcin, and TNFα remained
stable (Supplemental Appendix 4). However, no
significant treatment difference was observed for
both the overall treatment effect over the 6-month
period as well as at each visit (Table 3).
Post hoc analysis
The effect of OLE was also assessed according to
the level of walking pain (VAS score at walking)
at baseline. Stratification was performed in three
groups based on walking pain: subjects with low
walking pain with a VAS score between 30 and 50
(n = 40 subjects), subjects with medium walking
pain with a VAS score above 50 and inferior to 62
(n = 40), and subjects with high walking pain with
a VAS score above 62 (n = 38). Sub-group analy-
ses showed significant treatment difference in
favor of the OLE. No effect was observed in sub-
jects with low pain intensity at walking at baseline
(Figure 3(a), (c) and (e)). In contrast, 6 months
of OLE treatment significantly increased the
KOOS global score and decreased pain at walk-
ing at month 6 in subjects with high walking pain
at baseline (Figure 3(b) and (f)). At 6 month, the
effect sizes (ESs) were 0.36 and 0.40 for KOOS
global score and the walking pain respectively.
Serum Coll2-1NO2 levels were not affected by
treatments, whether the pain when walking is
high or low (Figure 3(c) and (d)).
The intensity of walking pain at baseline had no
significant impact on the effect of OLE on serum
biomarker levels and VAS at rest (Tables 2 and 3).
Compliance and bioavailability
The percentage of compliance was high at each
visit, with median compliance always superior to
93% and the first quartile above 87%.
The four metabolites of oleuropein (oleuropein
aglycone, homovanillyl alcohol, hydroxytyrosol,
and an isomer of homovanillyl alcohol were sig-
nificantly increased in urine of OLE-treated sub-
jects compared to placebo. The metabolites levels
rapidly increased and reached a steady state after
one month (Supplemental Appendix 5).
Adverse effects
Among 114 AEs, 67 occurred in the placebo group
and 47 in the OLE group. The most frequent AE
in both groups according the MedDRA System
Organ Class (SOC) were gastrointestinal disorders
(abdominal pain, nausea, dyspepsia; 6 (8.96%) in
placebo vs 7 in OLE group (14.89%)) and muscu-
loskeletal and connective tissue disorders (arthralgia
and back pain; 22 (32.84%) in placebo vs 12 (25.53%)
in OLE group) (Supplemental Appendix 6). No sig-
nificant difference in terms of number of subjects
Figure 2. Effects of OLE on global KOOS (a) score and on serum Coll2-1NO2 (b).
MN Horcajada, M Beaumont et al.
journals.sagepub.com/home/tab 9
Table 2. Estimates of treatment differences by visits between OLE and placebo group in FAS population.
LS mean (SE) 95% CI p value
KOOS global Overall 2.58 (2.41) [–2.2;7.36] 0.29
T1 0.56 (2.01) [–3.43;4.54] 0.78
T3 3.39 (2.9) [–2.36;9.14] 0.25
T6 3.79 (3.31) [–2.77;10.35] 0.25
kOOS pain Overall 2.88 (2.64) [–2.34;8.1] 0.28
T1 2.07 (2.35) [–2.59;6.73] 0.38
T3 3.07 (3.16) [–3.19;9.33] 0.33
T6 3.5 (3.59) [–3.61;10.61] 0.33
KOOS Adl Overall 0.16 (2.52) [–4.84;5.16] 0.95
T1 –2.02 (2.22) [–6.42;2.38] 0.37
T3 0.15 (2.95) [–5.71;6] 0.96
T6 2.35 (3.51) [–4.61;9.31] 0.51
KOOS symptom Overall 1.74 (2.24) [–2.71;6.18] 0.44
T1 1.08 (2.09) [–3.06;5.21] 0.61
T3 1.77 (2.76) [–3.7;7.23] 0.52
T6 2.37 (3.11) [–3.8;8.54] 0.45
KOOS sport Overall 3.06 (3.8) [–4.47;10.59] 0.42
T1 0.03 (3.72) [–7.34;7.41] 0.99
T3 4.98 (4.5) [–3.93;13.89] 0.27
T6 4.16 (5.14) [–6.03;14.35] 0.42
KOOS Qol Overall 3.56 (2.69) [–1.77;8.89] 0.19
T1 0.58 (2.53) [–4.44;5.6] 0.82
T3 6.44 (3.38) [–0.25;13.13] 0.06
T6 3.66 (3.6) [–3.47;10.8] 0.31
Knee pain VAS score at
rest
Overall 3.6 (3.1) [–2.6;9.7] 0.26
T1 7.1 (3.5) [0.2;14.1] 0.04
T3 3.5 (4.1) [–4.6;11.7] 0.39
T6 0.01 (4) [–7.9;7.9] 1
Knee pain VAS score at
walking
Overall 0.9 (3.6) [–6.2;8.1] 0.79
T1 6.3 (3.3) [–0.3;12.8] 0.06
(Continued)
Therapeutic Advances in Musculoskeletal Disease 14
10 journals.sagepub.com/home/tab
with at least one AE or severity of AE was observed
between the two treatment groups.
Discussion
In this study, we report the results of a placebo-
controlled randomized clinical trial investigating
the clinical efficacy of OLE administered orally
during 6 months in subjects with knee pain, dis-
comfort, and loss of mobility. This is the first study
investigating the effects of OLE in knee pain/dis-
comfort in a fully controlled prospective multi-
center trial. This study indicates that OLE at the
posology tested had no significant effect on knee
pain and function in an aged population without
diagnosed OA. However, OLE improved KOOS
score and reduced walking pain in subjects with
high pain at baseline. This effect corresponds to an
ES of 0.05 for pain at walking at 1 month, increas-
ing to 0.27 at 3 months to reach 0.40 at 6 months,
corresponding to a higher ES than that observed
with paracetamol.19 Similarly, in this sub-group,
KOOS global score was also significantly increased
after 6 months of treatment with a corresponding
ES of 0.36 at 6 months.
The beneficial effects of OLE on pain and loco-
motion were not associated with any adverse
effect after 6 months of treatment. This is in line
with toxicological studies in Wistar rat in which
no adverse effect was observed after 90-day inges-
tion of the highest dose tested (1000 mg/kg
bw/d).20 Considering the adverse effects of
NSAIDs and analgesic, mainly in patients with
comorbidities, OLE could be of value as an alter-
native to these drugs in pain management of
active subjects.21 One strength of this study was
that oleuropein levels have been measured in the
urine of subjects to evaluate the compliance and
the bioavailability of the product. Oleuropein
metabolites levels raised rapidly in the urine of all
treated subjects but remained undetectable or
very low in the placebo group. This clearly dem-
onstrates a good bioavaibility of the main metab-
olites of OLE, oleuropein aglycone, hydrotyrosol
and homovanillyl alcool and its isomer, and sug-
gests that the typical diet of the participants of the
study do not provide significant levels of dietary
oleuropein. The OLE supplement was well-toler-
ated, and compliance with the study protocol was
excellent.
LS mean (SE) 95% CI p value
T3 –1.4 (4.6) [–10.5;7.7] 0.75
T6 –2 (4.8) [–11.6;7.6] 0.68
30 second chair test Overall 0.3 (0.5) [–0.7;1.2] 0.59
T1 0.1 (0.5) [–0.9;1.1] 0.86
T3 0.3 (0.6) [–0.8;1.4] 0.61
T6 0.4 (0.6) [–0.8;1.6] 0.52
Stair test Overall –0.1 (1.5) [–3;2.8] 0.94
T1 –0.1 (1.4) [–2.8;2.7] 0.96
T3 –0.1 (1.3) [–2.7;2.5] 0.96
T6 0.2 (1.5) [–2.8;3.3] 0.88
Timed up and go Overall 0.2 (0.38) [–0.6;0.9] 0.68
T1 0.1 (0.39) [–0.7;0.9] 0.77
T3 0.4 (0.48) [–0.5;1.4] 0.39
T6 0 (0.46) [–1;0.9] 0.92
CI, confidence interval; KOOS, Knee injury and Osteoarthritis Outcome Score; LS, Least Squares; SE, standard error; VAS,
Visual analog scale.
Table 2. (Continued)
MN Horcajada, M Beaumont et al.
journals.sagepub.com/home/tab 11
Another key observation from this study was the
absence of OLE effect on inflammatory blood
parameters compared to placebo. Except the level
of PGE2 which decreased over time, the other
markers of inflammation remained stable until
the sixth month. This partially corroborated the
Table 3. Estimates of treatment differences by visits between OLE and placebo group for different biomarkers
in FAS population.
LS mean (SE) 95% CI p value
Coll2-1NO2 (pg/mL) Overall 242 (155) [–67;550] 0.12
T1 122 (197) [–269;512] 0.54
T3 241 (157) [–71;554] 0.13
T6 362 (245) [–124;848] 0.14
Coll2-1 (nM) Overall 21.31 (27.06) [–32.33;74.96] 0.43
T1 19.95 (29.14) [–37.8;77.7] 0.5
T3 8.37 (30.28) [–51.63;68.37] 0.78
T6 35.62 (38.87) [–41.53;112.77] 0.36
PGE2 (pg/mL) Overall –22 (64.1) [–149;105] 0.73
T1 –48.2 (113.7) [–274;177] 0.67
T3 23.5 (79.2) [–134;181] 0.77
T6 –41.2 (68.3) [–177;94.3] 0.55
CTX1 (ng/mL) Overall 0.03 (0.014) [0;0.05] 0.09
T1 0.02 (0.018) [–0.01;0.06] 0.22
T3 0.04 (0.02) [0;0.08] 0.05
T6 0.02 (0.019) [–0.02;0.05] 0.45
Osteocalcin (ng/mL) Overall 0.19 (0.38) [–0.56;0.94] 0.62
T1 0.33 (0.39) [–0.45;1.11] 0.41
T3 –0.04 (0.45) [–0.93;0.85] 0.93
T6 0.28 (0.58) [–0.87;1.43] 0.63
IL-8 (pg/mL) Overall –1.53 (4.26) [–9.98;6.92] 0.72
T1 –8.61 (4.85) [–18.21;1.00] 0.08
T3 3.26 (10.74) [–18.04;24.56] 0.76
T6 0.76 (1.91) [–3.03;4.56] 0.69
TNF-alpha (pg/mL) Overall –0.01 (0.09) [–0.19;0.17] 0.95
T1 –0.09 (0.1) [–0.29;0.11] 0.36
T3 –0.04 (0.11) [–0.26;0.18] 0.73
T6 0.11 (0.13) [–0.15;0.38] 0.4
CI, confidence interval; LS, least squares; SE, standard error.
Therapeutic Advances in Musculoskeletal Disease 14
12 journals.sagepub.com/home/tab
data of de Bock et al.5 demonstrating that OLE
increased plasma IL-6 but did not modulated
C-reactive protein (CRP), IL-8, and TNF-α lev-
els. In contrast to these authors, we have not
observed IL-6 levels modification after OLE
treatment. This difference can be explained by
differences in the population recruited. We have
recruited healthy elderly people while de Bock
et al.5 have enrolled younger overweigth volun-
teers. Another explanation could be the origin
and/or the genotype of the olive used to make the
extract. Oleuropein was the primary component
of olive leaves extract and exhibiting a content of
21.0 to 98.0 mg/g extract according the geno-
type.22 In addition, no effect of OLE was observed
on the cartilage degradation biomarkers Coll2-1
and Coll2-1NO2. This was not anticipated as
previous animal studies suggested a preventive
effect of OLE on cartilage degradation in OA
model and a decrease of Coll2-1 and PGE2. In
STR/ort mice, OLE supplementation starting at
the initial stages of OA, can suppress OA progres-
sion evaluated by histological scores.23 Similarly,
oleuropein treatment for 31 weeks prevented
joint degeneration and osteoarthritis in Dunkin–
Hartley guinea pigs that spontaneously develop
OA,10 and was superior to other polyphenols such
as rutin and curcumin. Interestingly, all polyphe-
nols significantly reduced the cartilage degrada-
tion score and Coll2-1NO2, but only oleuropein
significantly decreased the synovial histological
score and serum PGE2 levels compared to the
Figure 3. Effects of OLE on global KOOS (a, b), serum Coll2-1NO2 (c, d) and walking pain (e, f) according
the level of walking pain at baseline. (a, c, e); subject included in the lowest tertile of pain; (b, d, f): subjects
included in the highest tertile of pain.
MN Horcajada, M Beaumont et al.
journals.sagepub.com/home/tab 13
control group. The preclinical benefits of oleuro-
pein were established in the context of advanced
OA where joint degradation was severe. It is
therefore difficult to anticipate the effect of OLE
on metabolic and structural changes occurring in
our experimental population with early symptoms
of loss of cartilage integrity.
Finally, our results suggest that oleuropein may
relieve nociceptive pain triggered by mechanical
strain that could be explained by its calcium chan-
nel blocker property.24 Indeed, N-type calcium
channels are important for neuronal excitability
and play a role in pain genesis. These channels
are known to be the major route for Ca2+ entry
into the nerve terminals of nociceptors and there-
fore, blockers of these channels would be expected
to produce antinociceptive effects by reducing
transmitter release.25
This randomized, double-blinded, placebo-con-
trolled trial, using well validated scientific meth-
ods (i.e. KOOS, ELISA, and OARSI core set)
complements previous findings. Indeed, there
have been four reports on the efficacy of olive
derivatives on joint diseases, of which three were
randomized controlled trials26–28 and one was a
small-scale uncontrolled trial.29 Subjects included
in these studies were patients with knee OA. An
intervention, in the form of topical (olive extract
and virgin olive oil)27,29 or oral supplementation
(olive extract and hydroxytyrosol)26,28 was given.
Comparison with a placebo26,28 or an analgesic
(piroxicam)27 was performed in three of the clini-
cal trials. Globally, it was reported that OLE sup-
plement can decrease pain and thus improve daily
activities in adults with OA.
This study showed promising effects of OLE on
joint dysfunction in older subjects with pain at
baseline but should also be interpretated with some
limitations. The main limitation relies on the char-
acteristic of the study population as we recruited
older subjects without OA diagnosis which had
early signs of joint discomfort but a continuum of
joint pain, knee function, and physical performance
at baseline. This heterogeneous population was
chosen to reflect the general aging population look-
ing for nutritional solutions to manage early symp-
toms of joint discomfort but reduced statistical
power and limited the chances of observing treat-
ment effects in subject with very limited joint dys-
function. The observation that OLE is efficacious
in the subset of the population with moderate to
high knee pain but without OA suggests that this
intervention allows to manage the symptoms of
joint dysfunction when they are prevalent but not
delay the apparition of these symptoms in a preven-
tive manner. Finally, recruited patients had in
mean a moderate pain at inclusion while we
observed an effect of OLE in only a part of patients
with high pain intensity. It is possible that this
choice to select patients with mild pain may have
led to a floor effect leading to the inability to actu-
ally measure changes from baseline.
Conclusion
In conclusion, daily intake of OLE in subjects
with low to moderate knee pain and loss of func-
tion did not improve knee functionality. Post hoc
analysis indicates that in the most painful subjects
OLE may reduce joint discomfort with a good
safety profile and a good compliance. Moreover,
this trial provides useful information for the
design of a larger phase-III clinical trial including
the sample size estimate, the choice of the dose,
and the selection of primary outcomes.
Acknowledgements
The authors would like to thank posthumously
Dr Chapelle for its important contribution at pro-
ject as well as C. Gimenez and S. Benet for their
technical support for oleuropein metabolites
analysis.
Author contributions
Marie-Noëlle Horcajada: Conceptualization;
Writing – original draft; Writing – review & editing.
Meaumont: Methodology; Writing – review &
editing.
Nicolas Sauvageot: Formal analysis;
Methodology; Writing – review & editing.
Laure Poquet: Formal analysis; Methodology;
Writing – review & editing.
Madleen Saboundjian: Conceptualization;
Funding acquisition; Writing – review & editing.
Berenice Costes: Data curation; Investigation;
Project administration; Writing – review & editing.
Peter Verdonk: Investigation; Writing – review
& editing.
Geoffrey brands: Investigation; Writing – review
& editing.
Jean Brasseur: Investigation; Writing – review
& editing.
Therapeutic Advances in Musculoskeletal Disease 14
14 journals.sagepub.com/home/tab
Didier Urbin-Choffray: Investigation; Writing
– review & editing.
Marc Vandenberghe: Investigation; Writing –
review & editing.
Karl Brabant: Investigation; Writing – review &
editing.
Kurt De Vlam: Investigation; Writing – review
& editing.
Werner Faché: Investigation; Writing – review
& editing.
Bernard Jandrain: Investigation; Writing –
review & editing.
Vincent Grek: Investigation; Writing – review &
editing.
Michel Malaise: Investigation; Writing – review
& editing.
Yves Henrotin: Conceptualization; Method-
ology; Resources; Supervision; Writing – original
draft; Writing – review & editing.
Conflict of interest statement
The authors declared the following potential con-
flicts of interest with respect to the research,
authorship, and/or publication of this article: YH
is the founder and chairman of Artialis SA, a spin-
off company of the University of Liège developing
biomarkers.
MNH, MB, NS, LP, and MS are employees of
Société des produits Nestlé SA.
ACH, BC, and LG are employees of the
Artialis’company.
Funding
The authors disclosed receipt of the following
financial support for the research, authorship,
and/or publication of this article: All the opera-
tional phase of this study (patient recruitment,
data collection, and statistical analysis) was
funded by Société des produits Nestlé SA.
Ethics Approval and Consent to Participate
The study protocol was approved by the Central
Ethics Committee of the University Hospital of
Liège in Belgium (namely Comité d’Ethique
Hospitalo-Facultaire Universitaire de Liège), agree-
ment number: 707. This RCT was also registered
on Clinical trial.gov on March 7th, 2017 (https://
clinicaltrials.gov/ct2/show/NCT03072108).
Consent for Publication
All authors have read the paper and agreed for its
publication
ORCID iD
Yves Henrotin https://orcid.org/0000-0003-
1073-449X
Supplemental material
Supplemental material for this article is available
online.
References
1. Calmbach WL and Hutchens M. Evaluation
of patients presenting with knee pain: part II.
Differential diagnosis. Am Fam Physician 2003;
68: 917–922.
2. Atiquzzaman M, Karim ME, Kopec J, etal.
Role of nonsteroidal antiinflammatory drugs
in the association between osteoarthritis and
cardiovascular diseases: a longitudinal study.
Arthritis Rheumatol 2019; 71: 1835–1843.
3. Bush TM, Shlotzhauer TL and Imai K.
Nonsteroidal anti-inflammatory drugs. Proposed
guidelines for monitoring toxicity. West J Med
1991; 155: 39–42.
4. Conaghan PG, Arden N, Avouac B, etal. Safety
of paracetamol in osteoarthritis: what does the
literature say. Drugs Aging 2019; 36: 7–14.
5. de Bock M, Thorstensen EB, Derraik JG, etal.
Human absorption and metabolism of oleuropein
and hydroxytyrosol ingested as olive (Olea
europaea L.) leaf extract. Mol Nutr Food Res
2013; 57: 2079–2085.
6. Omar SH. Oleuropein in olive and its pharmaco-
logical effects. Sci Pharm 2010; 78: 133–154.
7. Feng Z, Li X, Lin J, etal. Oleuropein inhibits
the IL-1β-induced expression of inflammatory
mediators by suppressing the activation of
NF-κB and MAPKs in human osteoarthritis
chondrocytes. Food Funct 2017; 8: 3737–3744.
8. Castejón ML, Ángeles Rosillo M, Montoya T,
etal. Oleuropein down-regulated IL-1β-induced
inflammation and oxidative stress in human
synovial fibroblast cell line SW982. Food Funct
2017; 8: 1890–1898.
9. Impellizzeri D, Esposito E, Mazzon E, etal.
Oleuropein aglycone, an olive oil compound,
ameliorates development of arthritis caused by
injection of collagen type II in mice. J Pharmacol
Exp Ther 2011; 339: 859–869.
MN Horcajada, M Beaumont et al.
journals.sagepub.com/home/tab 15
10. Horcajada MN, Sanchez C, Scalfo FM, etal.
Oleuropein or rutin consumption decreases the
spontaneous development of osteoarthritis in the
Hartley guinea pig. Osteoarthritis Cartilage 2015;
23: 94–102.
11. Puel C, Mardon J, Kati-Coulibaly S, etal. Black
Lucques olives prevented bone loss caused by
ovariectomy and talc granulomatosis in rats. Br J
Nutr 2007; 97: 1012–1020.
12. Puel C, Quintin A, Agalias A, etal. Olive oil and
its main phenolic micronutrient (oleuropein)
prevent inflammation-induced bone loss in the
ovariectomised rat. Br J Nutr 2004; 92: 119–127.
13. Puel C, Mathey J, Agalias A, etal. Dose-
response study of effect of oleuropein, an olive
oil polyphenol, in an ovariectomy/inflammation
experimental model of bone loss in the rat. Clin
Nutr 2006; 25: 859–868.
14. Visioli F and Galli C. Biological properties of
olive oil phytochemicals. Crit Rev Food Sci Nutr
2002; 42: 209–221.
15. Casado-Díaz A, Anter J, Müller S, etal.
Transcriptomic analyses of the anti-adipogenic
effects of oleuropein in human mesenchymal
stem cells. Food Funct 2017; 8: 1254–1270.
16. Santiago-Mora R, Casado-Díaz A, De
Castro MD, etal. Oleuropein enhances
osteoblastogenesis and inhibits adipogenesis: the
effect on differentiation in stem cells derived from
bone marrow. Osteoporos Int 2011; 22: 675–684.
17. Filip R, Possemiers S, Heyerick A, etal. Twelve-
month consumption of a polyphenol extract
from olive (Olea europaea) in a double blind,
randomized trial increases serum total osteocalcin
levels and improves serum lipid profiles in
postmenopausal women with osteopenia. J Nutr
Health Aging 2015; 19: 77–86.
18. Mobasheri AL, Lambert C and Henrotin Y.
Coll2–1 and Coll2–1NO2 as exemplars of collagen
extracellular matrix turnover – biomarkers to
facilitate the treatment of osteoarthritis? Expert Rev
Mol Diagn 2019; 19: 803–812.
19. Bannuru RR, Schmid CH, Ken DM, etal.
Comparative effectiveness of pharmacologic
interventions for knee osteoarthritis: a systematic
review and network meta-analysis. Ann Intern
Med 2015; 162: 46–54.
20. Clewell AE, Béres E, Vértesi A, etal. A
comprehensive toxicological safety assessment
of an extract of Olea Europaea L. Leaves
(Bonolive™). Int J Toxicol 2016; 35: 208–221.
21. Hayes CJ, Krebs EE, Hudson T, etal. Impact
of opioid dose escalation on the development of
substance use disorders, accidents, self-inflicted
injuries, opioid overdoses and alcohol and non-
opioid drug-related overdoses: a retrospective
cohort study. Addiction 2020; 115: 1098–1112.
22. Orak HH, Karamac´ M, Amarowicz R, etal.
Genotype-related differences in the phenolic
compound profile and antioxidant activity of
extracts from olive (Olea europaea L.) leaves.
Molecules 2019; 24: 1130.
23. Takuma M, Haruka K, Mutsuto W, etal. Olive
leaf extract prevents cartilage degeneration in
osteoarthritis of STR/ort mice. Biosci Biotechnol
Biochem 2018; 82: 1101–1106.
24. Zare L, Esmaeili-Mahani S, Abbasnejad M,
etal. Oleuropein, chief constituent of olive
leaf extract, prevents the development of
morphine antinociceptive tolerance through
inhibition of morphine-induced L-type calcium
channel overexpression. Phytother Res 2012; 26:
1731–1737.
25. Malfait AM and Miller RJ. Emerging targets
for the management of osteoarthritis pain. Curr
Osteoporos Rep 2016; 14: 260–268.
26. Bitler CM, Matt K, Hook G, etal. Olive extract
supplement decreases pain and improves
daily activities in adults with osteoarthritis
and decreases plasma homocysteine in those
with rheumatoid arthritis. Nutr Res 2007; 27:
470–477.
27. Bohlooli S, Jastan M, Nakhostin-Roohi B, etal. A pilot
double-blinded, randomized, clinical trial of topical
virgin olive oil versus piroxicam gel in osteoarthritis of
the knee. J Clin Rheumatol 2012; 18: 99–101.
28. Takeda R, Koike T, Tanaka K, etal. Double-
blind placebo-controlled trial of hydroxytyrosol
of Olea europaea on pain in gonarthrosis.
Phytomedicine 2013; 20: 861–864.
29. Gelmini F, Ruscica M, Macchi C, etal.
Unsaponifiable fraction of unripe fruits of olea
europaea: an interesting source of anti-inflammatory
constituents. Planta Med 2016; 82: 273–278.
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