Table 6 The 20 most frequently occurring keywords

1

oxidative stress

636

11

rheumatoid-arthritis

140

2

osteoarthritis

318

12

nitric-oxide

139

3

expression

256

13

activation

128

4

chondrocyte

227

14

gene-expression

120

5

cartilage

206

15

cartilage degradation

118

6

knee osteoarthritis

180

16

in-vitro

94

7

nf-kappa-b

167

17

antioxidant

91

8

apoptosis

157

18

disease

81

9

inflammation

156

19

lipid-peroxidation

77

10

articular-cartilage

155

20

model

75