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 (R2 = .36, P = .02) and medial shift of the femur (R2 = .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.
Hamai, Okazaki, Murakami, Nakahara, Mizu-uchi, Akasaki, and Iwamoto are with the Department of Orthopaedic Surgery, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan. Ikebe and Higaki are with the Department of Mechanical Engineering, Faculty of Engineering, Kyushu Sangyo University, Fukuoka, Japan. Shimoto is with the Department of Mechanical Engineering, Faculty of Engineering, Fukuoka Institute of Technology, Fukuoka, Japan.