The aim of this study was to determine external and internal loads on the knee joint during downhill walking with and without hiking poles. Kinematic, kinetic and electromyographic data were collected from eight males during downhill walking on a ramp declined at 25 degrees. Planar knee joint moments and forces were calculated using a quasi-static knee model. The results were analysed for an entire pole-cycle as well as differentiated between single and double support phases and between each step of a pole-cycle. Significant differences between downhill walking with and without hiking poles were observed for peak and average magnitudes of ground reaction force, knee joint moment, and tibiofemoral compressive and shear forces (12-25%). Similar reductions were found in patellofemoral compressive force, the quadriceps tendon force and the activity of the vastus lateralis; however, because of a high variability, these differences were not significant. The reductions seen during downhill walking with hiking poles compared with unsupported downhill walking were caused primarily by the forces applied to the hiking poles and by a change in posture to a more forward leaning position of the upper body, with the effect of reducing the knee moment arm.