title: Hidden osteophyte formation on plain X-ray is the predictive factor for development of knee osteoarthritis after 48 months--data from the Osteoarthritis Initiative.
abstract: OBJECTIVE
  To examine whether the detection of osteophytes anywhere in the knee could serve as a pre-radiographic biomarker for osteoarthritis (OA) development.
  
  
  METHODS
  Baseline magnetic resonance imaging (MRIs) of 132 participants in the Osteoarthritis Initiative (OAI) were studied. Based on radiographs, 66 knees were assessed as osteoarthritis-free (no-osteoarthritis [NOA], or Kellgren/Lawrence [K/L] severity grade 0/1 both at baseline and 48 months), and another 66 knees were assessed as having radiographic OA changes (pre-radiographic osteoarthritis [PROA], or with K/L grade 0/1 at baseline and grade ≥ 2 at 48 months). Using baseline MRI data, we examined eight sites of osteophyte formation: the medial and lateral femoral condyle (MFC and LFC, respectively); medial and lateral tibial plateau (MTP and LTP, respectively); medial and lateral facets of the patellofemoral joint (PM and PL, respectively); tibial spine (TS); and femoral intercondylar notch (IC). Knee joint osteophyte size was assessed via the 8-point marginal osteophytes item of the whole-organ magnetic resonance imaging score (WORMS). The frequencies and distributions of osteophytes were compared between groups.
  
  
  RESULTS
  Mild-size osteophytes (defined as score ≥ 2) were observed more frequently at the MFC (P = 0.00278), MTP (P = 0.0046), TS (P = 0.0146), PM (P < 0.0001), PL (P = 0.0012), and IC (P < 0.0001) in PROA knees than in NOA knees. Moderate-size osteophytes (defined as score ≥ 4) were more frequently observed in PROA knees than in NOA knees only at the IC (P < 0.0001).
  
  
  CONCLUSIONS
  Knees with osteophyte formation at the IC, even those of K/L severity grade 0/1, are at risk for the development of radiographic OA by 48 months.
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: joe_katsuragi@hotmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Katsuragi
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: sasho@faculty.chiba-u.jp.
authors.forename: T
authors.initials: T
authors.lastname: Sasho
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: y-satoshi@mvb.biglobe.ne.jp.
authors.forename: S
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Chiba University Hospital Clinical Research Center, Japan. Electronic address: yasu@faculty.chiba-u.jp.
authors.forename: Y
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of General Medical Services, Division of Radiology, Graduate School of Medicine, Chiba University, Japan. Electronic address: atsuyan1@chiba-u.jp.
authors.forename: A
authors.initials: A
authors.lastname: Watanabe
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: ryuichiro.akagi@gmail.com.
authors.forename: R
authors.initials: R
authors.lastname: Akagi
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: yt.muramatsu@gmail.com.
authors.forename: Y
authors.initials: Y
authors.lastname: Muramatsu
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: muko.524729@gmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Mukoyama
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: kkaazzuu54@yahoo.co.jp.
authors.forename: Y
authors.initials: Y
authors.lastname: Akatsu
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: fukawataisuke0625@yahoo.co.jp.
authors.forename: T
authors.initials: T
authors.lastname: Fukawa
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: orthopaedics@hotmail.co.jp.
authors.forename: J
authors.initials: J
authors.lastname: Endo
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: hiorokohoshi@yahoo.co.jp.
authors.forename: H
authors.initials: H
authors.lastname: Hoshi
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: yo_hey210@hotmail.com.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: t.sasaki020581@gmail.com.
authors.forename: T
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Japan. Electronic address: 19501114@faculty.chiba-u.jp.
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000368:Aged; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000473:pathology; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000473:pathology; D054850:Osteophyte / Q000000981:diagnostic imaging* / Q000473:pathology; D057071:Patellofemoral Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D011859:Radiography
keywords: Intercondylar notch; Magnetic resonance imaging; Osteoarthritis; Osteoarthritis Initiative; Osteophyte formation; Pre-radiographic osteoarthritis