Abstract
Knowledge of joint kinematics in the lower limb is important for understanding joint injuries and diseases and evaluating treatment outcomes. However, limited information is available about the joint kinematics required for high flexion activities necessary for floor sitting life style. In this study, the hip and knee joint kinematics of ten healthy male and ten healthy female subjects were investigated using an electromagnetic motion tracking system. We measured the hip and knee joints' functions moving into 1) kneeling on knees with legs parallel without using arms, 2) kneeling on knees with legs parallel with using arms, 3) kneeling on knees with one foot forward without using arms, 4) cross-legged sitting, 5) kneeling with legs to the side, 6) sitting with legs stretched out, and 7) deep squatting, and moving out of the above seven conditions. Conditions 1) through 3) were Japanese seiza style. On conditions 4) through 7), arms were not used. We further measured the functions of putting on and taking off a sock under such conditions as 8) with standing position and 9) sitting position (Fig 1). Here special attention was paid for flexion and extension motion. The data were used to produce the pattern of joint angulation against the percentage of the cycle for each individual conducting each activity. The kinematic curves were split into 3 phases: moving into the rest position, the rest position and out of the rest position. It should be noted that the moving into and the rest phases were split at the moment when the peak value was determined during the moving into phase. Thus the initiation of the rest phase on the curve was not coinciding with the moment the subject reached at the rest position. This was necessary in order not for the mean kinematic curve to become too dull in shape. Same was true when the end of rest phase was determined. The maximum hip and knee joint angles during the cycle were determined. Further a relationship between the hip and knee joint excursions were investigated. The results indicated condition 8) requires the maximum flexion angles to the hip among all conditions, 157.5 ± 20.4° and condition 3) to the knee joint, 157.1 ± 10.0° respectively (Fig 2). The results also indicated in many activities, the maximum joint angles were recorded not during the rest phase but during the moving into or out of phase. In any conditions even including donning on and off a sock, a strong relationship was found between the hip and knee joints motion (Fig 3), indicating the bi-articular muscles' co-contraction during the sit to stand activities. The data presented in this study will increase the knowledge of high-flexion needs especially in non-Western cultures and provide an initial characterization of the prosthesis kinematics in high flexion.
