In Vivo Kinematics of Healthy and Osteoarthritic Knees During Stepping Using Density-Based Image-Matching Techniques.

The purpose of this study was to investigate in vivo kinematics in healthy and osteoarthritic (OA) knees during stepping using image-matching techniques. Six healthy volunteers and 14 patients with a medial OA knee before undergoing total knee arthroplasty performed stepping under periodic anteroposterior radiograph images. We analyzed the three-dimensional kinematic parameters of knee joints using radiograph images and CT-derived digitally reconstructed radiographs. The average extension/flexion angle ranged 6°/53° and 16°/44° in healthy and OA knees, with significant difference in extension (P = .02). The average varus angle was -2° and 6° in healthy and OA knees, with a significant difference (P = .03). OA knees showed 1.7° of significantly larger varus thrust (P = .04) and 4.2 mm of significantly smaller posterior femoral rollback (P = .04) compared with healthy knees. Coronal limb alignment in OA knees significantly correlated with varus thrust (R(2) = .36, P = .02) and medial shift of the femur (R(2) = .34, P = .03). Both normal and OA knees showed no transverse plane instability, including anteroposterior, mediolateral directions, or axial rotation. In conclusion, OA knees demonstrated different kinematics during stepping from normal knees: less knee extension, larger varus thrust, less posterior translation, and larger medial shift.