title: Posterior-anterior weight-bearing radiograph in 15 degree knee flexion in medial osteoarthritis.
abstract: OBJECTIVE
  To evaluate the degree of knee flexion at which: (1) degenerative joint space narrowing is best seen, (2) the tibial plateau is best visualized and (3) the tibiofemoral angle is most correct, in order to assess the degree of flexion in the anteroposterior radiographic view that is most useful for assessing medial compartment osteoarthritis (OA) of the knee.
  
  
  METHODS
  We compared the conventional extended view of the knee and views at 15 degrees, 30 degrees, and 45 degrees of flexion with respect to joint space narrowing, alignment of the medial tibial plateau (MTP), and tibiofemoral angles in 113 knees of 95 patients with medial osteoarthritis of the knee (22 men, 73 women; mean age 67 years).
  
  
  RESULTS
  At the midpoint and the narrowest point of the medial compartment, joint space narrowing values at 15 degrees, 30 degrees, and 45 degrees of flexion of the knee were smaller than that of the conventional extended view. Superimposition of the margins of the tibial plateau was satisfactory in 12% of patients in the conventional extended view, in 36% at 15 degrees of flexion, in 20% at 30 degrees of flexion, and in 19% at 45 degrees of flexion of the knee. When the knee was at 15 degrees of flexion there was a smaller difference in the tibiofemoral angle, in comparison with the knee extended, than was the case at 30 degrees and 45 degrees of flexion in patients with medial OA.
  
  
  CONCLUSIONS
  A posteroanterior view with 15 degrees of flexion of the knee was able to detect joint space narrowing accurately, to achieve good alignment of the MTP in the medial compartment, and to reduce the difference in tibiofemoral angle compared with a view of the knee in conventional extension, and may be an alternative view in cases of medial OA of the knee.
authors.affiliation: Department of Orthopaedic Surgery, Kochi Medical School, Nankoku, Japan. norioy@mail2.netwave.or.jp
authors.forename: Norio
authors.initials: N
authors.lastname: Yamanaka
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Takahashi
authors.forename: Norikazu
authors.initials: N
authors.lastname: Ichikawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamoto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011187:Posture; D011859:Radiography; D012016:Reference Values; D016474:Weight-Bearing / Q000502:physiology*