[Stress on the femoropatellar joint in downhill walking--a biomechanical study]

Kinematic and kinetic data were collected of 6 male and 6 female healthy subjects. For downhill walking a dismountable slope of 6 m length and a grade of 19.3% was built. Planar net joint moments and mechanical power at the knee joint were calculated for the sagittal view using force platform records based on standard inverse dynamics procedures. On the basis of a two dimensional knee model the patello femoral joint compressive forces were calculated. While the maximal extension moment for level walking was only 1.2 +/- 0.5 Nm/kg bw at a knee flexion angle of 20 degrees it was 2.6 +/- 0.6 Nm/kg bw at an angle of 40 degrees for downhill walking. This increased moment and knee flexion angle yields a 3 to 4 times bigger femoropatellar joint compressive force for downhill walking compared to level walking. Due to a smaller moment arm of female subjects the patello femoral joint compressive forces were bigger for females compared to males (14 N/kg bw for male subjects, 18 N/kg for female subjects during level walking and 50 N/kg bw for male subjects, 70 N/kg for female subjects during downhill walking). The femoropatellar joint compressive force for downhill walking is comparable to running, squatting or downstairs walking. Based on this investigation downhill walking must be considered a strenuous task for the femoro patellar joint and explains well why patients with anterior knee pain or osteoarthritis have problems during downhill walking.