Allied Health Faculty Presentations


Reliability of Lower Limb Frontal Plane Alignment Measures Obtained with the Use of a Computer Program and Electronic Tools

Document Type

Poster Session

Event Date



World Congress on Osteoarthritis


Fort Lauderdale, FL


Purpose: This study determined the inter-reader and intra-reader reliability of lower limb frontal plane alignment measures obtained from digital radiographs using a computer software program. Methods: Measurements of lower limb frontal plane alignment were obtained from over 3000 full limb digital radiographs of both limbs of persons with or at risk for developing knee osteoarthritis (OA), as part of the Multicenter Osteoarthritis Study (MOST). Three trained clinicians used a computer software program (Horizon Image Viewer, version 1.5, OAISYS Medical Inc.) to locate bone landmarks on the femur and tibia from which standard measures of alignment [e.g. the Hip-Knee-Ankle (HKA) angle] could be computed. To assess the reliability of these alignment measurements, 100 randomly chosen digital radiographs, representing 200 limbs, were selected from the complete data set for a repeated analysis carried out two or more weeks after completion of the first measurements. Random effects 2-way analysis of variance (ANOVA) models were applied to estimate the interclass and intraclass correlation coefficients (ICC), which correspondingly evaluated inter-reader and intra-reader reliability for each of the angles and bone lengths. Results: High reliability measures were obtained for the HKA angle [inter-reader reliability: ICC=0.995 (95% CI, 0.994-1); intra-reader reliability: ICC= 0.998 (95% CI, 0.998-1)]. Reliability for additional angles between the femur and tibia ranged from 0.839 to 0.993 (inter-reader reliability) and 0.908 to 0.998 (intra-reader reliability). High reliability measures were also obtained for bone lengths (inter-reader reliability: ICC from 0.993 to 0.995; intra-reader reliability: ICC from 0.994 to 0.995). Conclusions: Each of the lower limb alignment and bone length measurements were highly reliable. The outcome supports the use of computer software programs and software tools for analysis of lower limb frontal plane alignment.


Front plane alignment