An analysis of hip joint loading during walking, running, and skiing

It was the purpose of this study to investigate loading of the hip joint during various skiing activities and to compare the results with walking and running. The results are relevant to determine which skiing activities can be recommended for patients after total hip replacement. Nine male subjects were instrumented with a 12-channel accelerometer system mounted on the upper body. Data were collected during walking, running, and six skiing activities and used as input for an inverse dynamic analysis that resulted in the time histories of the intersegmental force and moment at the supporting hip joint. Joint contact force was computed using a simple muscle model. Peak values were determined, averaged over all loading cycles, and compared between activities. Intersegmental force, indicating the influence of upper body weight and accelerations, was highest during running. Intersegmental moments were highest during the alpine skiing activities and indicated large extensor muscle forces at the hip joint. The peak joint contact force during walking at 1.5 m x s(-1) was 2.5+/-0.3 times body weight (BW). Running at 3.5 m x s(-1) produced a joint contact force of 5.2+/-0.4 BW during the push-off phase. Joint contact forces during four different alpine skiing conditions ranged from 4.1+/-0.6 BW (long turns, flat slope) to 7.8+/-1.5 BW (short turns, steep slope). Cross-country skiing had lower hip joint loading than running but higher than walking: 4.0+/-1.1 BW for classical technique and 4.6+/-0.6 BW for skating technique. Assuming that walking is a "safe" activity for a hip prosthetic patient, controlled alpine skiing and cross-country skiing appear relatively safe with respect to the magnitude of loading. However, the skiing activities showed considerably higher mediolateral and anterior-posterior forces than walking. Mechanical testing of prosthetic devices with loading conditions specific to these activities is needed to assess the effect of these force components on hip prostheses and to allow interpretation with respect to potential effects of skiing for a hip prosthetic patient.