Obesity-related juvenile form of cartilage lesions: A new affliction in the knees of morbidly obese children and adolescents

Abstract

Overweight and obesity are afflictions that lead to an increased risk of health problems including joint problems. The aim of the study was to assess the condition of articular cartilage in obese adolescent patients suffering from knee pain.
MRI of 24 knees of 20 morbidly obese patients, mean age 14.2 years, was performed in an open 1.0 Tesla MR system, where the cartilage, the quality and structure of the menisci, and the presence or absence of surrounding changes was examined.
In all patients a cartilage lesion in at least one region of the knee could be detected. Retropatellar cartilage lesions have been found in 19 knees. Ten cartilage lesions grade I, and four lesions grade II have been described in the lateral compartment of the knee, whereas the medial compartment showed in eight cases a grade I, in 13 cases a grade II and in two cases a grade III cartilage lesion. Meniscal changes were assessed in most patients.
Morbidly obese children and adolescents show major abnormalities in the articular cartilage of the knee. Whether obesity alone is the causal factor for the development of the pattern of these changes, remains to be seen. KEY POINTS : • Morbidly obese children and adolescents often suffer from knee pain • Prospective study showed cartilage and meniscal lesions in morbidly obese adolescents • MRI is an adequate tool for assessing cartilage lesions even in morbidly obese patients • It is unclear whether cartilage abnormalities are mainly due to mechanical overload.

Full text

MAGNETIC RESONANCE
Obesity-related juvenile form of cartilage lesions:
a new affliction in the knees of morbidly
obese children and adolescents
Harald K. Widhalm &Stefan Marlovits &Goetz H. Welsch &Albert Dirisamer &
Andreas Neuhold &Martijn van Griensven &Rudolf Seemann &Vilmos Vécsei &
Kurt Widhalm
Received: 14 May 2011 / Revised: 10 July 2011 / Accepted: 18 July 2011 / Published online: 21 September 2011
#European Society of Radiology 2011
Abstract
Objectives Overweight and obesity are afflictions that lead
to an increased risk of health problems including joint
problems. The aim of the study was to assess the condition
of articular cartilage in obese adolescent patients suffering
from knee pain.
Methods MRI of 24 knees of 20 morbidly obese patients,
mean age 14.2 years, was performed in an open 1.0 Tesla
MR system, where the cartilage, the quality and structure of
the menisci, and the presence or absence of surrounding
changes was examined.
Results In all patients a cartilage lesion in at least one
region of the knee could be detected. Retropatellar cartilage
lesions have been found in 19 knees. Ten cartilage lesions
grade I, and four lesions grade II have been described in the
lateral compartment of the knee, whereas the medial
compartment showed in eight cases a grade I, in 13 cases
a grade II and in two cases a grade III cartilage lesion.
Meniscal changes were assessed in most patients.
Conclusion Morbidly obese children and adolescents
show major abnormalities in the articular cartilage of
the knee. Whether obesity alone is the causal factor for
H. K. Widhalm (*):S. Marlovits :V. Vécsei
Center for Joints and Cartilage, Department of Traumatology,
Medical University of Vienna,
Vienna, Austria
e-mail: harald.widhalm@meduniwien.ac.at
S. Marlovits
e-mail: Stefan.marlovits@meduniwien.ac.at
V. Vécsei
e-mail: Vilmos.vecsei@meduniwien.ac.at
G. H. Welsch
MR Center, Department of Radiology,
Medical University of Vienna,
Vienna, Austria
e-mail: welsch@bwh.harvard.edu
G. H. Welsch
Department of Trauma Surgery, University Hospital of Erlangen,
Erlangen, Germany
A. Dirisamer
Department of Radiology, Medical University of Vienna,
Vienna, Austria
e-mail: Albert.dirisamer@meduniwien.ac.at
A. Neuhold
Department of Radiology, Private Hospital Rudolfinerhaus,
Vienna, Austria
e-mail: A.neuhold@rudolfinerhaus.at
M. van Griensven
Ludwig Boltzmann Institute for Experimental
and Clinical Traumatology,
Vienna, Austria
e-mail: martijn.van.griensven@lbitrauma.org
R. Seemann
Department of Cranio-Maxillofacial and Oral Surgery,
Medical University of Vienna,
Vienna, Austria
e-mail: Rudolf.seemann@meduniwien.ac.at
K. Widhalm
Division of Nutrition and Metabolism, Department of Pediatrics,
Medical University of Vienna,
Vienna, Austria
e-mail: Kurt.widhalm@meduniwien.ac.at
Eur Radiol (2012) 22:672–681
DOI 10.1007/s00330-011-2281-5

the development of the pattern of these changes,
remains to be seen.
Key Points
•Morbidly obese children and adolescents often suffer
from knee pain
•Prospective study showed cartilage and meniscal lesions
in morbidly obese adolescents
•MRI is an adequate tool for assessing cartilage lesions
even in morbidly obese patients
•It is unclear whether cartilage abnormalities are mainly
due to mechanical overload
Keywords Magnetic resonance imaging .Adolescents .
Obesity .Knee pain .Cartilage lesions
Introduction
In the last two to three decades the prevalence of
overweight children has doubled in the United States [1].
Furthermore, prevalence rates of morbid obesity in child-
hood and adolescence (defined as body mass index [BMI]
above the 99.5th percentile for age and sex) registered a
dramatic rise both in the USA [2–4] and in Europe [5–7].
Among overweight children in the European Union,
it is estimated that there are at least 3 million obese
children, and the number will increase by more than
85,000 each year [8].
Presently, at least one out of five children in the USA is
overweight and similar figures have been reported in
Europe. Interestingly the highest prevalence of obesity in
the paediatric age seems to be in the Mediterranean region
[9]. Excess body weight is the sixth most significant risk
factor contributing to the overall burden of disease
worldwide, whereas obesity represents one of the most
important public health issues (World Health Organisation—
Food and Agriculture Organisation [WHO-FAO], 2002) [10].
There are estimations that over 22 million children under
the age of 5 are severely overweight worldwide [11].
Referring to several studies, obese children often show
serious co-morbidities such as dyslipidaemia, insulin
resistance and impaired glucose tolerance [12] as well as
non-alcoholic fatty liver disease, sleep apnoea and asthma
[13–15]. Even cardiovascular diseases, like cardiomyopa-
thy and hypertension are linked to childhood obesity [10,
16–18], which could be an important early risk factor for
adult morbidity and mortality [19–21].
Additionally early structural changes in arteries and
impaired endothelial function can be observed in morbidly
obese children, moreover a proinflammatory state has been
detected in obesechildren, accompanied by functional vascular
changes like inter-cellular adhesion molecule 1 (ICAM-1) and
vascular cell adhesion molecule 1 (VCAM-1) [22].
In obese adults, joint problems such as arthritic or
degenerative changes, especially of the knee and hip
region, often occur [23]. Additionally, musculoskeletal
disorders [24,25]suchasslippedcapitalfemoral
epiphysis, Blount’s disease, forearm fracture or flat feet
are reported occasionally, however, there are very few
reports with regard to alterations in cartilage, which are
associated with remarkable pain in severely obese subjects,
especially in obese adolescents.
Magnetic resonance imaging has been reported to be the
gold standard in establishing the diagnosis and monitoring
of cartilage lesions in the knee joints. Owing to restrictions
regarding available MR systems with which morbidly
obese patients can undergo MRI, few studies are available
on the constitution of articular cartilage in the knee joint in
morbidly obese patients. To the best of our knowledge,
there are no reports of joint abnormalities in adolescents
with severe forms of obesity.
We hypothesised that in young subjects with morbid
obesity, who reported painful knee problems, morphological
and structural changes in the cartilage might be the cause of
the complaints. Therefore, the aim of the present study was to
confirm this hypothesis by means of high-resolution MR
using an open MRI system.
Materials and methods
Definition of study cohort
The study was carried out according to the Helsinki
Declaration, was approved by the local ethical committees
and written, informed consent was obtained from all
patients before enrolment. For the present study, the
database of the Department of Pediatrics, Division of
Nutrition and Metabolism, of the Medical University of
Vienna was screened for morbidly obese children, who
were admitted between January 2002 and April 2007
because of being severely overweight.
Patients, who took part in this study, had to meet the
following inclusion criteria: subjects had to be between
8 and 20 years of age and morbidly obese, BMI
exceeding the 99.5th percentile using the German curves
for children and adolescents according to Kromeyer-
Hauschild et al. [26]
Patients with regular medications like painkillers or
psychotropic drugs, or those who had suffered trauma,
which could have caused knee pain, were excluded. The
data were analysed retrospectively, retrieving both, anthro-
pometric data as well as additional anamnestic information.
Patients identified were sent after an examination by a
paediatric specialist in obesity (K.W.) to the outpatient
clinic of the Department of Trauma Surgery, Division for
Eur Radiol (2012) 22:672–681 673

Joints and cartilage, where they had to undergo several
examinations. The detailed basic anthropometrical data of
the study population are listed in Table 1.
Of the total number of 505 overweight (>90th BMI-
percentile for age) patients who were referred to the
department between 2002 and 2007, 50 subjects had to be
classified as being morbidly obese. Twenty morbidly obese
patients—4% of the whole group—complained about
painful knee joints and were therefore selected for
participating in the study. Children’s pain occurred regular-
ly after a few minutes of walking or running, so that they
were unable to do exercise using their knees.
For this study 20 morbidly obese patients, BMI > 99.5th
percentile, mean BMI 39.8 kg/m
2
, mean weight 107.4 kg,
mean age 14.2 years (9–19 years), who were suffering from
chronic knee pain, have been included. Sixteen of these
patients reported severe pain in one of their knees, and
further four patients complained about pain in both knees.
For this reason, 20 patients have been included in this
study, but 24 knees in 20 patients were examined. Because
there is no clear pathophysiological concept with regard to
the possible cause of knee pain in obese children and
adolescents, the following procedure has been established.
Design of the examination setting
Participating subjects were examined in underwear
(± 0.1 kg), and body weight was measured in the morning
in the fasting state on a scale. A comprehensive clinical
investigation of the whole body, particularly of the joints of
the painful knees was conducted. Principally the lower
extremities were examined according to the patient’s
mechanical axis and the collateral ligaments of the knees.
The testing of the stability of the knees was followed by the
Lachman test [27], to obtain information about the cruciate
ligaments, and tests concerning lesions of the menisci were
also accomplished. The exterior aspect of the knee
concerning swelling, effusion and reddening was appraised
and the knee was measured precisely concerning the
diameter of the joint, the height and the breadth. To
measure the extent of the patient’s knee mobility, the knees
were moved passively by the investigator.
Clinical description
Participating children and adolescents had to fill in a
standardised questionnaire according to the “CARRERA”
Sheet (CARRERA: CARtilage REpair Registry Austria), in
order to describe the clinical symptoms of patients suffering
from cartilage lesions and to follow-up surgical cartilage
repair procedures. This questionnaire includes questions
according to the level of pain in different activities of daily
living. It is a standardised evaluation system that was
created for the description of cartilage repair procedures in
a nationwide registry [28]. For the analysis used in this
study, subjective patient evaluation of validated scores was
used, specifically, the Visual Analogue Score (VAS) and the
Knee Injury and Osteoarthritis Outcome Score (KOOS)
[29–31]. KOOS is a 42-item self-administered, self-
explanatory questionnaire that covers five patient-relevant
dimensions, which were scored separately. Scores are
transferred to a 0–100 scale, with zero representing extreme
knee problems and 100 representing no knee problems [31]
and scores between 0 and 100 representing the percentage
of the total possible achievable score [32]. Results are
provided in Table 2.
MR imaging
After completing the clinical examination, an MRI of the
painful knees was performed in a special 1.0-Tesla open
Panorama MRI tool (Panorama HFO High Field, Philips,
Netherlands).
A standardised MRI examination protocol was used and
the following four sequences were performed for each
patient:
1. Sagittal PDW TSE: FOV 180 mm, rFOV 162 mm/90%,
TR 1400 ms, TE 25 ms, 3-mm thickness. Matrix: 512*512.
2. Sagittal 3D WATS: FOV 180 mm, rFOV 160 mm/89%,
TR 20 ms, TE 7.9 ms, 3-mm thickness. Matrix: 512*512.
3. Coronal PDW TSE SPIR: FOV 190 mm, rFOV
190 mm/100%, TR 1500 ms, TE 60 ms, 4-mm
thickness. Matrix: 256*256.
4. Axial T2 TSE: FOV 150 mm, rFOV 150 mm/100%,
TR 5897 ms, TE 100 ms, 3-mm thickness. Matrix:
512*512.
MRI and grading of cartilage and meniscal lesions
All the MR images have been reviewed by two independent
radiologists who have experience in musculoskeletal
diagnostic of 7 and 22 years respectively. After separate
diagnostic sessions the radiologists have agreed on each
score in a final consensus session. Tables given in results
only show these values.
Table 1 Basic anthropometrical data
Age Height Weight BMI
Years cm kg kg/m
2
Mean 14.2 162.5 107.4 39.8
Max 19.1 190.0 201.0 65.6
Min 9.5 144.0 60.0 28.6
SD 2.8 12.6 38.9 10.7
674 Eur Radiol (2012) 22:672–681

MRI and grading of cartilage lesions
Lesions of the cartilage were evaluated using the modified
version of the Outerbridge Classification following the
International Cartilage Repair Society (ICRS) [33–36].
According to the localisation and the extent of the cartilage
lesions, four different grades had been analysed and
evaluated.
Grade 0 indicated a normal cartilage situation with no
abnormalities and no signal alterations in the MR sequences;
Grade I was characterised by abnormal intra-chondral signal
on the MR sequences but normal cartilage surface. Grade II
was assigned if the articular surface showed further irregular-
ities and a loss of the cartilage thickness of less than 50%, or if
a separation between the superficial and deep cartilage layers
was observed. A lesion was assigned as Grade III when severe
surface irregularity with focal loss of 50% to 100% of the
cartilage thickness was detected. If there was a complete
chondral defect with bruising of the subchondral bone noted
then it was assigned to Grade IV. The cartilage was assessed
within three compartments of the knee joint: medial femo-
rotibial, lateral femorotibial and patellofemoral. In compart-
ments with multiple cartilage lesions of different grades, the
most severe grade was used to classify the compartment. For
the overall Outerbridge classification, the most severe grade of
the whole knee was used.
MRI and grading of meniscal lesions
Meniscal lesions were also analysed by MRI and classified
into three grades according to Stoller et al. [37]: MR grade I
represented one or several punctate signal intensities not
contiguous with an articular surface, grade II was a linear
intrameniscal signal intensity without articular surface
extension and grade III lesions of the meniscus were
characterised by signal intensities, which showed an
extension to at least one articular surface.
Statistical methods
Normal distribution of cartilage, meniscal score and
effusion was tested by means of the Shapiro test of
normality. The coefficient of overweight was tested in a
t-test. To decide whether children and adolescents with
BMI above the 99.5th percentile and knee pain show
damage to the cartilage, a t-test was performed (H0: μ=0;
H1: μ>0) for several parameters. As two parameters out of
three did not show normal distribution, parameters were
equally tested with non-parametric tests (Table 3). Addi-
tionally a Wilcox signed rank test was conducted, which
was used in the case of several variables that were not
normally distributed (Table 4). A Bonferroni correction was
applied in a second step to compensate for multiple testing.
Table 2 Characteristics of the
study sample
a
Median instead of mean and
median absolute deviation (mad)
instead of standard deviation
b
Number of patients with a
Baker cyst in round brackets
Characteristic Subjects (n=20)
Mean SD Range
Age—years 14.2 2.8 [9.5–19.1]
Female Sex—no. (%) 9 (45%)
Body mass index 39.8 10.7 [28.6–65.6]
Height 162.5 12.6 [144.0–190.0]
Weight 107.4 38.9 [60.0–201.0]
Characteristics of the knees
Brittberg
a
20[1–3]
IKDC 67.2 13.6 [44.83–90.8]
Koos—quality of life 63.9 18.6 [37.5–93.8]
Koos—pain 74.1 17.2 [38.9–97.2]
Koos—sport 61.2 25.4 [15.0–90.0]
Koos—symptoms 67.0 7.6 [53.6–78.6]
Koos—daily activity 84.6 8.8 [70.6–100.0]
Noyen 71.2 16.7 [40.0–100.0]
Tegener/Lysholm 4.5 2.0 [1.0–6.0]
Visual analogue scale
a
5 1.5 [1–7]
Outerbridge—cartilage
a
3 2.7 [1–7]
Meniscal lesion score
a
1.5 0.7 [0–4]
Effusion (volume in mL) 1.4 2.0 [0.0–6.9]
Baker cyst (volume in mL)
b
2.9 (n=7) 2.7 [0.7–8.1]
Eur Radiol (2012) 22:672–681 675

Interobserver reliability of radiological scores (i.e. cartilage
and meniscal scores) was determined by means of Cohen’s
Kappa, percentage of agreement in detailed scores as well
as percentage of agreement on existence of pathologic
scores. Statistics were performed with open source software
package R.
Results
Descriptive statistics of the 20 patients are displayed in
Table 1. Patients (11 male/9 female), with an average age of
14.2 years (range 9–19 years) showed a mean BMI (body
mass index) of 39.8 kg/m
2
(range 28.6 and 65.6 kg/m
2
). On
the MRI, meniscus tears have been identified in 16 out of
20 patients. In three cases a bone bruise in at least one
location was seen (Fig. 1), in two patients the bone bruise
was located in the medial compartment and in one
patient in the lateral compartment. Baker cysts were
detected in ten patients, and in seven patients the cyst
was greater than 5 cm
2
.
In all 24 knees of 20 patients cartilage lesions were
detected in at least one region of the knee joint. In 23
knees a lesion of the articular cartilage could be
described in the medial femorotibial (Fig. 2)andin14
knees in the lateral femorotibial compartment. In 19 knee
joints a cartilage defect was found in the retropatellar
(patellofemoral) region (Fig. 3).
Five juvenile subjects did not have any alteration in the
retropatellar cartilage. Nevertheless all four patients with
bilateral knee pain showed retropatellar lesions in both knee
joints. Out of 24 knees, there was a clearly diagnosed
intrachondral signal alteration in nine cases and hence a
diagnosed grade I lesion according to the Outerbridge
classification, in eight cases a grade II, and in two cases a
grade III lesion of the retropatellar cartilage.
In 8 out of 24 knees a grade I cartilage lesion was detected
in the medial compartment, a grade II lesion was diagnosed in
13 knee joints, and a grade III lesion was exposed in two cases
in the medial compartment of the knee joints.
In the lateral compartment a lesion of the cartilage was
only rarely found. Out of 24 knee joints, a grade I lesion
was detected in ten knees, and a grade II cartilage lesion
according to the modified Outerbridge classification in four
knees. None of the subjects showed any grade III lesion in
the lateral compartment. No grade IV lesions, characterised
by a full thickness defect of the cartilage with bruising of
the subchondral bone were detected using MRI. The
evaluation of the menisci revealed in the medial meniscus
a grade I lesion in ten knees and a grade II lesion in seven
Table 3 Analytical statistics: t-test of damage to cartilage, lesions of the menisci or effusion. Outermost column on the right shows pvalue of
Shapiro-Wilk normality test
Parameter Test value Degrees of freedom p= 95% CI pof Shapiro-Wilk
t-Test of cartilage score t= 8.13 df = 19 6.6E-8 [2.9 –∞] 0.093
t-Test of meniscal score t=5.82 df=19 6.7E-6 [1.12 –∞] 0.049
t-Test of effusion t=3.2 df= 19 0.0024 [0.64 –∞] 2.9E-5
Table 4 Non-parametric test.
Wilcox signed rank test with
continuity correction. The
outermost column to the right
shows Bonferroni-corrected
pvalues
a
H0: μ=0, H1: μ>0
b
H0: mean(x) => μgiven
in round brackets, H1:
mean(x)< μ
c
H0: mean(x) <= μgiven
in round brackets, H1:
mean(x)> μ
Parameter V pvalue Adjusted p value
Outerbridge cartilage score
a
210 4.5E-5 5.8E-4
Meniscal score
a
136 2.1E-4 2.7E-3
Effusion (volume in mL)
a
171 1.0E-4 1.3E-3
Baker cyst (volume in mL)
a
28 1.1E-2 0.15
IKDC
b
(μ=80) 7 3.9E-3 5.1E-2
Koos—quality of life
b
(μ=80) 12 1.0E-2 0.14
Koos—pain
b
(μ=80) 36 0.26 1.0
Koos—sport
b
(μ=80) 8.5 1.6E-2 0.21
Koos—symptoms
b
(μ=80) 0 8.1E-4 1.1E-2
Koos—daily activity
b
(μ=80) 69 0.95 1.0
Noyen
b
(μ=80) 14.5 5.3E-2 0.69
Tegener/Lysholm
c
(μ=6) 0 2.8E-2 0.37
Visual analogue scale
c
(μ=3) 80 8.3E-3 0.11
676 Eur Radiol (2012) 22:672–681

knee joints. The lateral meniscus showed changes in 12
knee joints with grade I lesions in eight knees and grade II
lesions in four knees. No grade III lesions were diagnosed
in the 24 knee joints.
Cartilage and menisci score, as well as effusion showed
significant abnormalities (Tables 3and 4). The results of the
Interobserver reliability are shown in detail in Table 5.
KOOS score was shown to be significantly reduced
regarding the symptoms dimension. Weak significances
were found for Baker cysts, IKDC, KOOS quality of life,
KOOS sport, Tegner and VAS scores (Table 4). Furthermore,
two young obese patients showed changes in the form of an
incipient osteoarthritis (Fig. 4). In five patients additionally
a plica mediopatellaris and a lateralisation of the patella was
seen. Further on the MRI the presence of joint fluid, Baker
cysts excluded, was observed and measured in 18 patients,
with an average size of 4.5 cm
2
. In one patient a grade III
osteochondritis dissecans was diagnosed.
Discussion
The present study demonstrates for the first time that in
morbidly obese children and adolescents, who suffer from
pains in their knees, marked morphological changes of the
cartilages from different grades and in different compartments
could be detected.
These defects are similar to those that can be seen in
patients who were victims of various accidents or immedi-
ate sequelae of traumatic influences, which can be found in
older people, due to mechanical injuries or as an inflam-
matory response to their joints. However, so far, those
changes have not been described in young subjects without
any traumatic history or any severe disease that could be
responsible for this damage. Moreover the observed Baker
cysts and effusions of greater extent, which were detected
in some of the young subjects could be interpreted as a sign of
osteoarthrosis or advancing lesions of the cartilage [38–40].
Fig. 1 Sagittal 3D WATS (a) and coronal PD TSE SPIR (b) MRI of
an 11-year-old young boy suffering from pain in his right knee with
no trauma. The patient is classified as morbidly obese with a height of
152 cm, a weight of 66 kg, exceeding a BMI of 28.6 kg/m
2
. Range of
motion of the young patient is 0-0-145. In athe cartilage lesion grade
1–2 according to Outerbridge in the medial compartment is seen
(white arrows). In bthe knee shows a marked bone bruise area in the
lateral tibial region predominantly (white arrows)
Fig. 2 Sagittal 3D WATS MRI of a 12-year-old young morbidly
obese patient of his right knee with a height of 159 cm, a weight of
77 kg, exceeding a BMI of 30.4 kg/m
2
. No trauma was responsible for
knee pain measured by the VAS score of 6. The two arrows mark the
region of the cartilage lesion in the medial compartment grade 3
according to Outerbridge. Furthermore, the MRI showed a lesion of
the medial meniscus, and a slight lateralisation of the patella with a
grade 2 cartilage lesion in the retropatellar area
Fig. 3 Sagittal PDW-TSE MRI sequence of a 12-year-old girl
complaining of severe knee pain in both of her knees with no
memorable trauma. The young girl corresponds to morbid obesity
classification indicating a BMI of 42.2 kg/m
2
. The patient exhibits a
genu valgus, with a hyperextension in the knees of 15 grade exceeding
a range of motion of 15-0-130. The region tagging between the two
white arrows in the femur and retropatellar region shows the
abnormalities within the cartilage
Eur Radiol (2012) 22:672–681 677

However, these lesions, which can often be found in adults,
have not been described in young subjects.
As summarised in Tables 3and 4morbid obesity shows
a significant impact on pathological MRI findings in knee
joints in children and adolescents. Especially typical
pathological signs such as cartilage and menisci lesions
(expressed in scores) and effusion were found. Whilst
cartilage scores showed to be reliable (Table 5), meniscal
scores depend more on the observer. The investigated
patients showed significant symptoms, which were mea-
sured by KOOS score.
In a recent Australian study, Anandacoomarasamy et al.
observed in about 50% of 111 severely obese adults (mean
BMI 39.9 ± 5.8%) marked lesions of the cartilage of the
knee [41]. Furthermore, they were able to show that the
percentage of cartilage lesions was associated with the
degree of obesity. The authors were able to show, that the
knee cartilage defects were associated with physical
disability and reduced knee range of motion, even after
accounting for the presence of clinical knee osteoarthritis.
Nevertheless, in this study, it does not come out clearly,
how many of those patients with cartilage lesions com-
plained of knee pain. In none of these patients cartilage
lesions have been observed in both knees. Additionally in
this study knee pain calculated, according to the WOMAC
Score, was associated with cartilage defect scores in all
compartments except the lateral tibiofemoral region, in
multivariate analysis.
In another study by the same group the authors were able
to describe knee cartilage lesions in the history of patients,
who had undergone knee replacement. It could be shown,
that the presence of cartilage lesions in the knee was
associated with BMI and decreased after a period of weight
loss [42]. The positive association between the presence of
knee cartilage lesions has been described by another
Australian group in 337 patients in 2005 with a preponderance
of these lesions in obese women.
A study by Ding et al. described in detail the association
between age and knee structural changes, measured by
cross-sectional MRI in a sample of 372 male and female
non-obese subjects, mean age 44 years [43]. They showed
that the most consistent knee structural changes with
increasing age are an enlargement in cartilage defect
severity and prevalence, cartilage thinning and an increase
in bone size.
Jones et al. were able to show, that in 74 healthy normal
weight children (9–18 years of age/mean BMI 20,5 kg/m
2
)
the cartilage volume in the tibial region, but not in the
patella bone, correlated significantly only with height, not
with weight. In overweight children the articular cartilage
volume did not differ significantly from the healthy normal
weight children.
Table 5 Interobserver reliability
measured with Cohen’sKappa
test; percentage of agreement in
all scores, percentage of
agreement of healthy (score 0) vs.
pathologic scores (scores >0)
Score Cohen’s Kappa Percentage agreement of scores Percentage agreement
of pathologic scores
Cartilage retropatellar 0.764 83.3 87.5
Cartilage medial 0.661 79.2 95.8
Cartilage lateral 0.670 79.2 83.3
Meniscus medial 0.563 70.8 79.2
Meniscus lateral 0.341 62.5 75.0
Fig. 4 Sagittal PDW-TSE (a–d) MRI of a morbidly obese young
male patient, 15 years of age, with a height of 168 cm, a weight of
170 kg, exceeding a BMI of 60.2 kg/m
2
. The patient complained of
severe knee pain for 2 years; it was observed that the intensity of the
pain was directly correlated with the young patient gaining weight.
The mean VAS score was 5, and the motion of the knee was slightly
reduced by a range of motion of 5-0-120. The images (a–d) show
abnormality in the form of an incipient knee arthrosis beginning in a
the lateral-most area dragging towards the medial, showing the medial
compartment, and a cartilage lesion grade 2–3 according to Outer-
bridge in the retropatellar region (white arrows)
678 Eur Radiol (2012) 22:672–681

The authors were also able to describe an interesting
phenomenon indicating that those children who participated
in vigorous sport programmes, gained twice as much
articular cartilage as those who participated less in sports
[44]. These data make it very likely that the observed
cartilage lesions in morbidly obese adolescents in our study
are due to overweight. The fact that those subjects could
not participate in vigorous sport programmes in previous
years, an additional factor that led to insufficient develop-
ment of an appropriate volume of the knee cartilage, might
be taken into consideration. An important question in that
regard is whether adolescents who are affected by those
cartilage lesions could be involved in any kind of sport
programmes, and if so, to what extent. Furthermore, the
question whether weight loss has the potential to lead to a
change or improvement in cartilage defect morphology
must be answered soon.
Another important question that therefore has to be
raised is whether these abnormalities are only due to
mechanical overload, or whether other possible metabolic
factors could be co-responsible for these changes. Due to
the fact that the observed cartilage changes are described in
detail for the first time, we are presently not able to provide
detailed pathophysiological mechanisms, which could
explain the underlying cause of the marked alterations.
However, these findings are of great interest, because one of
the cornerstones for the treatment of severe obesity is physical
activity. These results make it clear that physical activity
without any professional diagnosis and observation is clearly
contraindicated and could be associatedwith further damage to
the knees due to uncontrolled movements of the joints.
One limitation of the study is the fact—due to a missing
of a permission of the ethical committee—that no control
group could be included. A further limitation is the lack of
a gold standard insofar as none of the studied subjects
underwent arthroscopy or any other surgical treatment of
their knees. Moreover no longitudinal observation of those
lesions is available so far and the present report represents a
novel cross-sectional evaluation of young morbidly obese
individuals with clinical symptoms. Nevertheless further
studies have to show whether these changes really lead to
early osteoarthritis in these patients and, furthermore, if these
changes can be reduced after substantial weight loss, which
could be achieved exclusively after bariatric surgery [45].
A further limitation of this study is that the image quality
is limited in the present MRI measurements, because of the
oversized knee joints and the open MR system used, and
the diagnosis of cartilage alterations together with early
osteoarthritic changes could already be well established.
It is currently unknown when these morphological
changes in children’s joints start to emerge and which
joints are predominantly affected. Furthermore it is not
quite clear, whether the described changes only occur at a
definite body weight, in the presence of a certain
metabolism derangement, or at certain changes in the
anatomy, in terms of alterations in the axis of the leg. As
no control group was included in this study, it would be of
interest to study whether these morphological changes,
which were shown on the MRI, can also be observed in
young subjects with overweight or obesity (BMI<99.5°).
The fact that it has been clearly shown by Jones et al. that
in normal weight in healthy children no lesions of the knee
cartilage could be detected, makes it more likely that
obesity is the main causal factor [44].
In addition, morbidly obese adolescents, who do not
suffer from any pain, should be examined by way of MRI
of the knees. Thereby, the status of all joints should be
assessed, with regard to whether certain joints were affected
more than the others. Further studies that cover this topic
more closely are being carried out at present and will
therefore provide more information in the near future.
Looking from a therapeutic point of view, it would be
relevant to carry out a knee arthroscopy with a possible
cartilage smoothing in addition to weight reduction.
Meanwhile, in the case of profound cartilage damage, it is
important to consider possible microfracturing. Another
method of reducing pain is the application of a hyaluronic
acid compound [46–48]. Correspondingly, obtaining a
steady state of cartilage morphology by means of the intake
of reconstructing substances, such as chondroitin sulphate
in the form of tablets is reasonable.
Morbidly obese children show severe damage to the
knee joints affecting (according to Table 4); abnormalities
correlate with reduced quality of life and pain. Future
therapy might be monitored using the KOOS score or the
IKDC score. Further studies should reassess these correla-
tions between knee changes and symptoms in a healthy
collective. MRI should be a good and diagnostically
valuable method and might be used to prove reversibility
of knee damage in morbidly obese children who reduce
their weight. Reversibility of cartilage damage might be
verified to depend on age and weight.
In conclusion children and adolescents with morbid
obesity and knee pain show significant lesions of the
cartilage, abnormal features within the menisci and effu-
sions. These patients are very likely to complain about loss
of quality of life. They experience pain and suffer arthrosis-
related symptoms. Morbidly obese children have significant
pain, due to the higher body weight, whereby higher forces
are having negative effects on children’s joints, so that they
are not able to do physical activity regularly, and increase
their weight further. It has been confirmed that many
morbidly obese patients have severely lesions of the
cartilage. Further research has to be done to ascertain
whether factors other than obesity are causal for these
marked changes.
Eur Radiol (2012) 22:672–681 679

Acknowledgements This study is part of a funded project of the
Jubilaeumsfonds of the Austrian National Bank, Project number
11977. There was no involvement of other sponsors.
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