Methodical clinical measurement of knee deformity

Abstract

The recognition of the pattern and severity of deformity in knee osteoarthritis has important implications in its management and prognosis. A number of methods can be used to assess and measure the coronal and sagittal knee alignment: clinical deformity measuring device like a goniometer, standard knee radiographs, hip-knee-ankle (HKA) radiographs, computer navigation systems, magnetic resonance scan, computerized tomographic scan or simply a surgeon’s subjective measurement. Each of these methods has advantages and disadvantages. The aim of this study was to compare three methods of measurement: clinical measurement with a goniometer; HKA radiographs and computer navigation. This study included 54 patients with arthritic knees, who underwent total knee replacement with computer navigation. The deformity in both coronal and sagittal planes was measured using the three methods and the results compared using Bland Altman limits of agreement. The clinical measurement differed greatly from radiographic and computer navigation measurements. According to Bland Altman limits of agreement clinical measurements could be up to 10° away from the radiographic or computer navigated measurements in coronal plane. In the sagittal plane the clinical measurements could be up to 12° away compared to computer navigation measurements. A combination of these measurements methods should be taken into account when assessing the deformity of a knee especially in relation to posture and weight bearing status. The methodical clinical measurement of knee deformity as described in this paper gives too wide a margin of error and should not be relied upon in isolation.