Is There an Alternative to the Full-Leg Radiograph for Determining Knee Joint Alignment in Osteoarthritis? RANA S. HINMAN, RACHEL L. MAY, AND KAY M. CROSSLEY Objective. To assess the concurrent validity of alternative measures of frontal plane knee alignment, namely the radiographic anatomic axis and 5 clinical measures, in medial compartment knee osteoarthritis (OA) as compared with the mechanical axis on radiograph. Methods. Forty individuals (mean  SD age 64.7  9.4 years) with symptomatic medial knee OA participated. Knee alignment was measured according to the following methods: lower-limb mechanical axis on radiograph, lower-limb anatomic axis on radiograph, visual observation, distance between medial knee joint lines or medial malleoli using a calliper, distance between a plumb line and medial knee joint line or malleolus using a calliper, tibial alignment using a gravity inclinometer, and lower-limb alignment using a goniometer. Data were analyzed using Pearson’s correlation coefficient or Spearman’s rho correlation coefficient and simple linear regression. Results. The anatomic axis best correlated with the mechanical axis (r  0.88), followed closely by the inclinometer method (r  0.80). Other clinical measures of alignment that were significantly associated with the mechanical axis were the calliper method, the plumb-line method, and visual observation (r  0.76, 0.71, and 0.52, respectively). However, the goniometer method failed to correlate. Conclusion. The anatomic axis on radiograph and the inclinometer method appear to be valid alternatives to the mechanical axis on full-leg radiograph for determining frontal plane knee alignment in medial knee OA. These alternative methods of measuring knee alignment may increase the assessment of this parameter by clinicians and researchers alike, given that malalignment is an important indicator of disease progression and treatment outcome. KEY WORDS. Knee; Osteoarthritis; Alignment; Validity; Radiograph. INTRODUCTION Knee osteoarthritis (OA) is a common affliction in the elderly population worldwide, affecting approximately one-third of individuals 60 years of age (1). Typical consequences for the patient with knee OA include pain, reduced physical function, disability, and ultimately de- creased quality of life. A range of musculoskeletal impair- ments are also associated with the condition. These may include, but are not limited to, muscle weakness, impaired proprioception, altered gait patterns, and joint laxity (2– 6). Because there is no cure for OA, current management strategies aim to relieve symptoms and slow the progres- sion of the disease (7,8). Joint malalignment in the frontal plane is a frequent manifestation of knee OA, but it is not clear whether it precedes disease onset or occurs as a consequence. Varus malalignment appears to be the most common deformity, and has been reported in 53–76% of individuals with knee OA (9 –11). This is probably a result of the high prevalence of medial tibiofemoral OA relative to lateral compartment disease (12,13), whereby progressive cartilage loss on the medial side may lead to increasing varus deformation of the knee joint. Frontal plane malalignment has important biomechanical consequences because it influences loading across the knee joint during weight bearing. In the neu- trally aligned knee, the ground reaction force vector passes medially to the joint center, creating an adduction moment that increases medial compartment forces relative to lat- Supported by funding from The University of Melbourne and the Arthritis Foundation of Australia. Rana S. Hinman, BPhysio(Hons), PhD, Rachel L. May, Kay M. Crossley, BAppSci(Physio), GradDip(Physio), PhD: Cen- tre for Health, Exercise and Sports Medicine, School of Physiotherapy, The University of Melbourne, Victoria, Aus- tralia. Address correspondence to Rana S. Hinman, BPhysio- (Hons), PhD, Centre for Health Exercise and Sports Medi- cine, School of Physiotherapy, The University of Melbourne, Parkville, Victoria, 3010, Australia. E-mail: ranash@ unimelb.edu.au. Submitted for publication May 20, 2005; accepted in re- vised form August 26, 2005. Arthritis & Rheumatism (Arthritis Care & Research) Vol. 55, No. 2, April 15, 2006, pp 306 –313 DOI 10.1002/art.21836 © 2006, American College of Rheumatology ORIGINAL ARTICLE 306