title: Constitutional varus does not affect joint line orientation in the coronal plane.
abstract: BACKGROUND
  In a previous study, we described the distribution of coronal alignment in a normal asymptomatic population and recognized the occurrence of constitutional varus in one of four individuals. It is important to further investigate the influence of this condition on the joint line orientation and how the latter is affected by the onset and progression of arthritis.
  
  
  OBJECTIVE
  The purposes of this study are (1) to describe the distribution of joint line orientation in the coronal plane in the normal population; (2) to compare joint line orientation between patients with constitutional varus and neutral mechanical alignment; and (3) to compare joint line orientation between a cohort of patients with prearthritic constitutional varus and a cohort of patients with established symptomatic varus arthritis.
  
  
  METHODS
  Full-leg standing hip-to-ankle digital radiographs were performed in 248 young healthy individuals and 532 patients with knee arthritis. Hip-knee-ankle (HKA) angle and tibial joint line angle (TJLA) were measured in the coronal plane. Patients were subdivided into varus (HKA ≤ -3°), neutral, and valgus (HKA ≥ 3°).
  
  
  RESULTS
  The mean TJLA in healthy subjects was 0.3° (SD 2.0°). TJLA was parallel to the floor in healthy subgroups with neutral alignment (TJLA 0.3°, SD 1.9) and constitutional varus (TJLA 0.2°, SD 2.2°). In patients with symptomatic arthritis and varus alignment, the TJLA opened medially (mean -1.9°, SD 3.5°).
  
  
  CONCLUSIONS
  Constitutional varus does not affect joint line orientation. Advanced medial arthritis causes divergence of the joint line from parallel to the floor. These findings influence decision-making for osteotomy and alignment in total knee arthroplasty.
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Ghent University Hospital, De Pintelaan 185, Gent, 9000, Belgium, jan.victor@ugent.be.
authors.forename: Jan M K
authors.initials: JM
authors.lastname: Victor
authors.forename: David
authors.initials: D
authors.lastname: Bassens
authors.forename: Johan
authors.initials: J
authors.lastname: Bellemans
authors.forename: Sarper
authors.initials: S
authors.lastname: Gürsu
authors.forename: Aad A M
authors.initials: AA
authors.lastname: Dhollander
authors.forename: Peter C M
authors.initials: PC
authors.lastname: Verdonk
mesh_terms: D000328:Adult; D017760:Bone Malalignment / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D009949:Orientation; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging*; D011859:Radiography; D012016:Reference Values