In this study the effects of joint moment and alignment of the lower extremity with osteoarthritis of the knee (OA) were investigated. We used a three-dimensional analysis system to measure the hip and knee moment of subjects standing on one leg. Pelvic obliquity was also calculated. Motion analysis system (VICON) and two force plates as measurement devices were used in the study. Thirteen markers were placed on each subject. Radiographically F.T.A., ∠TDK, ∠CFK, ∠LGA, FD/TD, FG/AG and grade of progress of OA were assessed. We learned that FTA, ∠LGA, FD/TD, and FG/AG became indices of hip abduction moment and the knee valgus moment of a dynamic factor by radiography. Knee valgus moment was shown to increase with progress of the disease. This dynamically corresponds to parting of the body center of the gravity line from the knee joint. Moreover, hip abduction moment was shown to decrease with progress of the disease. The pelvic obliquity angle in all OA groups reduced on the side of the swing leg. It seems varus deformity of the knee joint caused progressive movement of the upper part of the body to the side of the standing leg. Therefore, it was supposed that there were two joint muscles which adhered to the pelvis, especially the participation of the tensor fascia lata, contributed to compensate for the progress of the knee OA. While standing, the tensor fascia lata is important realignment of the lower body. We suggest that biarticular muscle dysfunction, especially of the tensor facia lata, correlated with the progress of OA. Advancement of varus deformity, strain of the tensor facia lata, muscle imbalance between the abductor and adductor muscles of the hip joint caused pelvic obliquity and medial shift of the gravity line.
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