Size of Medial Knee Osteophytes Correlates With Knee Alignment But Not With Coronal Laxity in Patients With Medial Knee Osteoarthritis

The severity of osteoarthritis (OA) has been related to osteophyte size. However, the effects on osteophyte size of repeated and increased loading associated with joint laxity and varus misalignment remain unclear. We investigated these relationships in patients with medial knee OA and compared the performances of computed tomography (CT) and radiography for assessing osteophyte parameters. We examined knee joint alignment on radiographs and knee laxity using arthrometry in 191 patients with medial knee OA who were undergoing total knee arthroplasty. We also measured femur and tibia osteophyte distance (largest perpendicular distance from the cortical line to outer margin of the osteophyte) using radiography and CT, osteophyte areas (largest area surrounded by the outer margin of an osteophyte) by CT and determined the locations of the osteophytes in the femur and tibia by CT. We then analyzed the correlations between the variables using Spearman’s rank correlation tests. Osteophyte sizes in the femur and tibia as determined by radiography (distance) or CT (distance and area) were positively correlated with the degree of varus alignment but not with medial or lateral laxity. There was also a significant correlation between maximum osteophyte distances measured by radiography and CT. The greatest number and the largest osteophytes were located in the posterior third of the femur and middle third of the tibia, respectively. Osteophyte size was correlated with preoperative knee alignment but not with knee laxity in patients with medial knee OA. Osteophyte size can be evaluated using conventional radiography, without the need for CT. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:639–644, 2020