title: Knee Images Digital Analysis (KIDA): a novel method to quantify individual radiographic features of knee osteoarthritis in detail.
abstract: OBJECTIVE
  Radiography is still the golden standard for imaging features of osteoarthritis (OA), such as joint space narrowing, subchondral sclerosis, and osteophyte formation. Objective assessment, however, remains difficult. The goal of the present study was to evaluate a novel digital method to analyse standard knee radiographs.
  
  
  METHODS
  Standardized radiographs of 20 healthy and 55 OA knees were taken in general practise according to the semi-flexed method by Buckland-Wright. Joint Space Width (JSW), osteophyte area, subchondral bone density, joint angle, and tibial eminence height were measured as continuous variables using newly developed Knee Images Digital Analysis (KIDA) software on a standard PC. Two observers evaluated the radiographs twice, each on two different occasions. The observers were blinded to the source of the radiographs and to their previous measurements. Statistical analysis to compare measurements within and between observers was performed according to Bland and Altman. Correlations between KIDA data and Kellgren & Lawrence (K&L) grade were calculated and data of healthy knees were compared to those of OA knees.
  
  
  RESULTS
  Intra- and inter-observer variations for measurement of JSW, subchondral bone density, osteophytes, tibial eminence, and joint angle were small. Significant correlations were found between KIDA parameters and K&L grade. Furthermore, significant differences were found between healthy and OA knees.
  
  
  CONCLUSIONS
  In addition to JSW measurement, objective evaluation of osteophyte formation and subchondral bone density is possible on standard radiographs. The measured differences between OA and healthy individuals suggest that KIDA allows detection of changes in time, although sensitivity to change has to be demonstrated in long-term follow-up studies.
authors: Rheumatology and Clinical Immunology, UMC Utrecht, The Netherlands. a.c.a.marijnissen@umcutrecht.nl
authors: A C A
authors: AC
authors: Marijnissen
authors: K L
authors: KL
authors: Vincken
authors: P A J M
authors: PA
authors: Vos
authors: D B F
authors: DB
authors: Saris
authors: M A
authors: MA
authors: Viergever
authors: J W J
authors: JW
authors: Bijlsma
authors: L W
authors: LW
authors: Bartels
authors: F P J G
authors: FP
authors: Lafeber
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000473:pathology; D054850:Osteophyte / Q000000981:diagnostic imaging; D011859:Radiography; D013977:Tibia / Q000000981:diagnostic imaging