Abnormal motion of the medial femoral condyle in lateral knee osteoarthritis.

The pattern of knee motion in patients with lateral osteoarthritis may be associated with the pathogenesis of this disease. Based on previous findings of decreased anteroposterior femoral condylar translation in knees with medial knee osteoarthritis, we asked whether a similar pattern of knee kinematics in lateral osteoarthritis could be related to the wear pattern on the tibial plateau. We used sequential radiostereometric images to study kinematics during active weightbearing extension in five knees with lateral osteoarthritis and 11 control knees. At 45 degrees of flexion, the posterior circular center of the lateral femoral condyle displaced posteriorly at 45 degrees and moved anteriorly during extension in both groups. There was also a proximal displacement with extension, but from a more distal position in the osteoarthritis group. We could only partly relate the kinematics of knees with lateral osteoarthritis to the wear pattern on the tibial plateau. Contrary to our hypothesis of normal anterior displacement of the medial and increased posterior displacement of the lateral femoral condyle, we observed no change of anterior-posterior displacements of the lateral condyle.