2014 Volume 22 Pages 15-26
Knowledge of joint kinematics in the lower limb is important for understanding joint injuries and diseases, and evaluating treatment options and outcomes. However, limited information is available about the kinematics of the lower limb joints in high flexion during floor sitting activities. In this study, we used an electromagnetic motion-tracking system to measure the hip and knee joint kinematics of ten healthy male and ten healthy female subjects sitting into and standing out of the following positions: kneeling on knees, sitting cross-legged, kneeling with legs to the side, sitting with legs outstretched, and deep squatting. We also measured the hip and knee kinematics when donning and removing a sock while standing or sitting on the floor, since they require the same high joint flexion required for floor sitting activities. First, the data were used to produce joint angulation patterns against the normalized time for each individual performing each activity. We proposed a way to split the kinematic curves into 3 to 5 phases in order to preserve the typical features of the original curve, even after statistically averaging all the curves. Next, the maximum hip and knee joint angles during each motion were identified directly from the original curves. Furthermore, the relationship between the hip and knee joint excursions was investigated. The results indicated that in most activities, the maximum joint angles did not occur during when resting on the floor but during the sitting or standing phase. Among all the activities, donning and removing a sock while standing required the maximum hip flexion angle of 157.5±20.4°, and the motion starting with one foot forward to sit into or to stand out of the kneeling required the maximum flexion angle on the forward knee of 157.1±10.0° respectively. In most of the motions investigated, a strong relationship was found between the hip and knee joint motions, indicating the bi-articular muscles’ co-contraction during the sit to stand activities.
