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Althea Medical Journal. 2017;4(2)

Vitamin C Intake and Risk Factors for Knee Osteoarthritis 

Nadia Ayu Destianti,1 Siti Nur Fatimah,2 Sumartini Dewi3
1Faculty of Medicine Universitas Padjadjaran, 2Department of Public Health Faculty of Medicine 

Universitas Padjadjaran, 3Department of Internal Medicine Faculty of Medicine Universitas 
Padjadjaran/Dr. Hasan Sadikin General Hospital Bandung

Abstract

Background: Knee osteoarthritis (OA) is a degenerative disease of the knee joints characterized by 
progressive softening and disintegration of articular cartilage. In OA, which is influenced by several risk 
factors, free radicals are increased by local ischemia in the cartilage. As an exogenous antioxidant, vitamin 
C also plays an important role in collagen and glycosaminoglycan synthesis. This study was carried out to 
identify vitamin C intake as well as risk factors in knee OA.
Methods: The study population was determined by non-probability sampling with convenient approach to 
knee OA patients at the Rheumatology Outpatient Clinic of Dr. Hasan Sadikin General Hospital in October–
November 2013. Data were obtained through questionnaire interview about risk factors, severity index of 
OA and vitamin C intake profile. Data presentation was conducted by descriptive method.
Results: There were 47 patients diagnosed with knee OA in the Rheumatology Outpatient Clinic. The result 
showed that 7 patients (14.9%) had low vitamin C intake for the last 3 months. There were 30 patients with 
family history of OA (63.8%). Thirty two patients (68.1%) were passive smokers, 44 patients (93.6%) had 
history of repeated use of knee joints and majority of respondents had obesity.  
Conclusions: Most of the subjects have sufficient vitamin C intake and more than half have risk factors that 
may contribute to the incidence of knee OA.

Keywords: Knee osteoarthritis, risk factors, vitamin C intake

Correspondence: Nadia Ayu Destianti, Faculty of Medicine, Universitas Padjadjaran, Jalan Raya Bandung-Sumedang Km.21, Jatinangor, 
Sumedang, Indonesia, Phone: +62 81224112223 Email: nadiaayud@gmail.com

Introduction

The disease pattern of the developing world 
has shifted from infectious and acute diseases 
to chronic and degenerative diseases.1 
Osteoarthritis (OA) is a degenerative joint 
disease associated with damage to the joint 
cartilage and one of the 10 most common 
disabilities in the developing country. The OA 
most frequently attacks the spine, hip, knee 
and ankle. The prevalence of OA is about 50–
60% from 23.6–31.3% of the total patients 
with joint disease in Indonesia.2 Prevalence of 
knee OA is quite high at 14.9% in women and 
8.7% in men.3

In OA, free radicals level elevated in 
cartilages by local ischemia degrade its 
components, triggering synovial and immune 
responses that promotes further cartilage 
damage.4 To protect the cells and organ 
systems, humans have evolved a highly 
sophisticated antioxidant protection system, 
which can be either naturally produced in situ 

(endogenous) or externally supplied through 
foods and supplements (exogenous). 

As one of the exogenous antioxidants, 
vitamin C is critical to bone health, acting as 
sulfate carrier in glycosaminoglycan synthesis 
which may be relevant to OA etiology because 
depletion of sulfated proteoglycans from 
the articular cartilage extracellular matrix 
is one of the earliest expressions of OA, 
which eventually leads to degeneration of 
the cartilage.5 Concentration of vitamin C in 
the body is mostly determined by its dietary 
intake. Adequacy of vitamin C in the body may 
help to slow down the progression of OA. 

The objectives of this study was to identify  
the dietary intake of vitamin C and risk factors 
for knee osteoarthritis 

Methods

This study was conducted in the Rheumatology 
Outpatient Clinic of Dr. Hasan Sadikin General 
Hospital Bandung, West Java, Indonesia 

AMJ. 2017;4(2):173–7

ISSN 2337-4330  ||  doi: http://dx.doi.org/10.15850/amj.v4n2.1067



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174     AMJ June 2017

from October to November 2013. This 
study was approved by the Health Research 
Ethics Commitee of the Faculty of Medicine, 
Universitas Padjadjaran. The sampling 
method used was non-probability sampling 
(convenience sampling) and the minimal 
sample needed for this study was determined 
through the categorical descriptive formula. 
Data was taken from 46 patients who were 
diagnosed as having knee osteoarthritis (OA) 
by doctors of the Rheumatology Outpatient 
Clinic of Dr. Hasan Sadikin General Hospital 
Bandung,  and was validated by the consultant of 
rheumatology. The subjects were patients who 
fulfilled the inclusion and exclusion criteria. 
The inclusion criteria were patients aged 
40–70 years as well as willing to answer the 
questions in the questionnaire. The exclusion 
criteria were patients with dementia, patients 
who had knee traumatic history and had 
undergone menisectomy (knee joint surgery). 
Furthermore, respondents were asked to sign 
the inform consent form, and then  interviewed 
using a questionnaire for identification of 
risk factors related to osteoarthritis. The 
Western Ontario and McMaster Universities 
Arthritis Index (WOMAC) form was used to 
classify respondents OA severity and the Food 
Frequency Questionnaire (FFQ) form to find 
out about the respondents dietary vitamin 
C intake for the last 3 months which were 
obtained through frequency and amount of 
fruit and vegetables that respondents ate every 
day or week or month. 

Respondents were asked to indicate  risk 
factors such as lifestyle information about 
smoking routine as well as history of smoking 
and passive smokers history at home, metabolic 
information about body weight history and 
body height, biomechanical factor information 
about occupational history and history of daily 
activities that included repeated use of knee 
joints, and genetic information about family 
history of knee OA. 

The WOMAC form consists of 24 questions 
divided into 3 parts. Part 1 is about the pain 
that the patient feels for the last 48 hours 
when doing 5 activities, for example: walking 
on a flat surface, going up and down stairs, 
disturbing pain at night while sleeping, sitting 
or lying and standing upright. Part 2 is about 
stiffness or a sensation of decreased ease in 
moving joint that the patient has in their knee 
during the last 48 hours while doing these 2 
activities: after awakening in the morning and 
after sitting, lying, or resting in the day. Part 
3 consists of 17 questions about difficulties 
the patient has experienced in doing daily 

physical activities due to the patient’s hip/
knee during the last 48 hours, this mean the 
ability to move around and look after oneself. 
Each of the questions is scaled from 0–10 by 
visual analog scale. Afterwards, each of the 
respondents’ severity indices are calculated 
and classified into 3 classes of OA severity 
from mild, moderate to severe.

The FFQ is a tool used to assess individual 
dietary intake history using a list of foods 
on which respondents report their usual 
consumption frequency over a given period. 
The quantitative food frequency used in this 
study included more precise food portion 
size estimates in household measures. The 
FFQ used in this study consisted of a list of 
fruit and vegetable containing vitamin C, 
their frequency every day, week and month as 
well as  each portion size. Seasonal fruit and 
vegetable were excluded in this questionnaire 
to minimize bias.

The statistical analysis was calculated 
by used of Microsoft Office Excel.  The 
presentation of data was performed by used 
of the descriptive method through frequency 
distribution tables about dietary intake of 
vitamin C, risk factors of knee OA and WOMAC 
severity index of OA.

Results

This study discovered that most of the 
patients were middle-aged females. Most of 
the respondents completed the senior high 
school (38.3%). Based on the respondent’s 
occupation, 46.8% were government employer 
(Table 1).

Dietary intake of vitamin C was assessed 
using the Food Frequency Questionnaire. 
This questionnaire assessed the daily fruit 
and vegetable containing vitamin C intake 
of respondents for the last 3 months. Only 7 
patients (14.9%) had low daily dietary intake 
of vitamin C (Table 2).

Furthermore, risk factors for knee OA were 
determined by what was presented, mostly 
the respondents were passive smokers in their 
home (68.1%) and 53.2% of the respondents 
had body mass index (BMI) more than 
normal which was divided into 2 categories, 
overweight and obese. More than a half of 
knee OA patients showed history of repeated 
use of knee joints in three categories, stood for 
2 hours or more (59.6%), walked for 2 hours 
or more (57.4%) and went up and down stairs 
for more than 2 times (51.1%). Family history 
was present in 25 patients (53.2%) (Table 3).

Knee OA severity of each patient was 



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Nadia Ayu Destianti, Siti Nur Fatimah, Sumartini Dewi: Vitamin C Intake and Risk Factors for Knee Osteoarthritis

Table 1 Characteristic of Respondents
Characteristic Frequency %

Sex
Female 42 89.4
Male 5 10.6
Age (years old)
< 50 7 14.9
50–60 26 55.3
> 60 14 29.8
Education level
Did not graduate elementary school 1 2.1
Graduated elementary school 6 12.8
Graduated junior high school 2 4.3
Did not graduate senior high school 1 2.1
Graduated senior high school 18 38.3
Graduated academy 10 21.3
Graduated scholar 8 17
Graduated magister 1 2.1
Occupation
Government employer 22 46.8
Entrepreneur 2 4.3
Retired 10 21.3
Housewife 12 25.5
Never worked 1 2.1

Table 2 Dietary Intake of Vitamin C Classification
RDA Classification Frequency %

Low (<75 mg) 7 14.9
Normal (75–1000 mg) 40 85.1
Excess (>1000 mg) 0 0
Total 47 100

Note : RDA = Recommended Dietary Allowance

assessed using the WOMAC form. There were 
41 patients (87.2%) with mild osteoarthritis 
and 6 patients (12.8%) with moderate 
osteoarthritis. There was no patient with 
severe osteoarthritis (Table 4).

Discussion

This study discovered that several risk 
factors contributed to the incidence of knee 

osteoarthritis. The percentage of people with  
knee OA aged less than 50 years was lower 
than those aged older than 50 years. This 
findings was similar to a study conducted  by 
Patil et al.6 The proportion of women with  
disorders was higher compared to men. A 
study carried out by Patil et al.6 also observed 
that OA is higher in women (65.7%) than 
men (34.3%). Patients, who graduated from 
academy and above, show lower incidence of 



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176     AMJ June 2017

knee osteoarthritis compared to the patients 
with lower educational level. It was suspected 
that the higher the level of education, the 
higher the level of knowledge and awareness 
of health was.

Based on the respondents’ characteristics, 
the public servants occupation showed a 
higher level of osteoarthritis (46.8%) than 
other occupations. This difference might be 
due to the lack of physical activity, mobility, 
social issues as well as work that put extra 
load on the knee joints (e.g. lifting patients and 

pushing beds for nurse as public servants).7
Dietary intake of vitamin C assessed by the 

Food Frequency Questionnaire showed 85.1% 
of patients had normal vitamin C intake based 
on Angka Kecukupan Gizi Indonesia (AKG), 
2004, while the rest of 14.9% patients had low 
level of vitamin C intake. This result roughly 
correlated with the literature which stated that 
higher plasma vitamin C is found in patients 
with lower grade of OA, and in this study 41 
patients (87.2%) had mild OA severity index.8

Other risk factors was smoking. This study 

Table 3 Risk Factors for Knee Osteoarthritis
Risk Factors Frequency %

Active smoker
Yes 4 8.5
Used to 6 12.8
No 37 78.7
Passive smoker
Yes 32 68.1
No 15 31.9
Body mass index
Normal 22 46.8
Overweight 9 19.2
Obese 16 34
History of repeated use of knee joints
Lifting/pushing heavy objects 20 42.6
Stands for 2 hours/more 28 59.6
Walks for 2 hours /more 27 57.4
Up and down stairs more than 2 times 24 51.1
Squat for more than 2 hours/repeatedly 15 31.9
Family history of knee osteoarthritis
Yes 25 53.2
No 21 44.7
Unknown 1 2.1

Table 4 Knee Osteoarthritis Severity
WOMAC Classification Frequency %

Mild (<=80) 41 87.2
Moderate (81–160) 6 12.8
Severe (>160) 0 0
Total 47 100

Note: WOMAC = The Western Ontario and McMaster Universities Arthritis Index



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revealed that most of the patients were passive 
smokers which proved the free radical theory 
of OA was caused by many factors such as 
smoking, both active and passive, pollutants, 
and free radicals produced by environment 
around the  patients.9 

More than half of the patients had body 
mass index higher than normal (53.2%), this is 
in agreement with the risk factors of OA found 
in the  study conducted by Patil et al.6 

Moreover, the history of repeated use of 
the knee was observed as 42.6% for lifting 
or pushing heavy objects, 59.6% for standing 
for 2 hours or more, 57.4% for walking for 
2 hours or more, 51.1% for climbing up 
and down stairs for more than 2 times and 
31.9% for squatting for more than 2 hours 
or repeatedly. These results agreed with the 
theory of repetitive use of knee joints as risk 
factors for developing knee OA. It was stated 
that workers performing repetitive tasks as 
part of their occupations for many years are 
at high risk of developing OA in the joints they 
use repeatedly for example, workers whose 
jobs require regular knee bending or lifting or 
carrying heavy loads have a high rate of knee 
OA.10

Additionally, osteoarthritis is also 
influenced by genetic factors such as familial 
history, it corresponded with the results of our 
study which showed more than a half of the 
patients (53.2%) had family history of knee 
osteoarthritis from their mother, father, or 
other siblings.10

This study had limitations. The use of 
food frequency questionnaire that rely on 
the patient’s memory may cause a recall bias. 
Moreover, to understand what the researcher 
asked and the patient’s cooperation may lead 
to bias. 

In conclusion, most of the respondents 
have sufficient profile of vitamin C intake. 
More than a half of the respondents have 
significant risk factors which may contribute 
to the incidence of knee osteoarthritis. These 
risk factors can be prevented with a healthy 
lifestyle as well as awareness of factors that 

may induce osteoarthritis in the later life.

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8. Naskar DS, Dawn DI, Sarkar DS, De DC, 
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Nadia Ayu Destianti, Siti Nur Fatimah, Sumartini Dewi: Vitamin C Intake and Risk Factors for Knee Osteoarthritis