title: The factors associated with pain severity in patients with knee osteoarthritis vary according to the radiographic disease severity: a cross-sectional study.
abstract: OBJECTIVE
  Knee osteoarthritis (OA) pain is suggested to be associated with inflammation and detrimental mechanical loading across the joint. In this cross-sectional study, we simultaneously examined the inflammation and alignment of the lower limb and examined how the pain components varied depending on the disease progression.
  
  
  METHODS
  One-hundred sixty female medial type of early- [n = 74 in Kellgren-Lawrence (K/L) 2] to advanced-stage (n = 96 in K/L >2) knee OA subjects (70.5 years on average) were enrolled. Knee pain was evaluated using a pain visual analog scale (VAS) and the pain-related subcategory of the Japanese Knee Osteoarthritis Measure (JKOM-pain). The serum interleukin (sIL)-6 level reflecting synovitis, and the high sensitivity C-reactive protein (hs-CRP) level were measured to evaluate the severity of inflammation. The anatomical axis angle (AAA) was measured as an alignment index. The β-coefficient was estimated after adjusting for age and the body mass index (BMI) using a multiple linear regression analysis.
  
  
  RESULTS
  Multiple linear regression analyses showed that the sIL-6 levels, but not AAA, associated with the pain VAS [β = 10.77 (95% confidence interval (CI): 4.14-17.40), P < 0.01] and JKOM-pain scores [β = 3.19 (95% CI: 1.93-4.44), P < 0.001] in the early stage. Conversely, AAA, but not the sIL-6 levels, was found to be associated with the pain VAS [β = -1.29 (95% CI: -2.51 to -0.08), P < 0.05] and JKOM-pain scores [β = -0.49 (95% CI: -0.82 to -0.16), P < 0.01] in the advanced stage.
  
  
  CONCLUSIONS
  The presence of a higher level of sIL-6 and the varus alignment of the joint is associated with pain in early- and advanced-stage knee OA patients, respectively.
authors: Department of Orthopedics, Juntendo Tokyo Koto Geriatric Medical Center, Tokyo, Japan. shimura@juntendo.ac.jp
authors: Y
authors: Y
authors: Shimura
authors: H
authors: H
authors: Kurosawa
authors: Y
authors: Y
authors: Sugawara
authors: M
authors: M
authors: Tsuchiya
authors: M
authors: M
authors: Sawa
authors: H
authors: H
authors: Kaneko
authors: I
authors: I
authors: Futami
authors: L
authors: L
authors: Liu
authors: R
authors: R
authors: Sadatsuki
authors: S
authors: S
authors: Hada
authors: Y
authors: Y
authors: Iwase
authors: K
authors: K
authors: Kaneko
authors: M
authors: M
authors: Ishijima
mesh_terms: D000368:Aged; D018771:Arthralgia / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000503:physiopathology; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000503:physiopathology; D010147:Pain Measurement; D011859:Radiography; D012307:Risk Factors; D012720:Severity of Illness Index; D013585:Synovitis / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000503:physiopathology; D016474:Weight-Bearing / Q000502:physiology
chemical_list: D015415:Biomarkers; C508600:IL6 protein, human; D015850:Interleukin-6; D002097:C-Reactive Protein
keywords: Alignment; Interleukin-6; JKOM (Japanese Knee Osteoarthritis Measure); Knee osteoarthritis; Pain; Synovitis