Introduction: A thigh push-off is often used as a compensation strategy for standing up by elderly people. However, the biomechanics of this movement are not known. In this thesis the standing-up movement with the use of the thigh push-off strategy (TP), the armrest push-off strategy (AR) and the no arm aid strategy (NA) was analysed. The aim was to find out why TP for standing up is being used as a compensation strategy by elderly people. Method: We examined upper and lower limb joint moments and lower limb muscle forces in three different sit-to-stand strategies in nine healthy elderly men. Inverse dynamics and static optimisation were done in OpenSim using a 3D musculoskeletal model. Results: The lumbar extension moment in TP was significantly lower compared to NA (p=0.04). Rectus femoris force is lower in phase 2 in TP compared to AR. AR upper limb joint moments were significantly larger in dominant and non-dominant shoulder external rotation (p=0.02, p<0.01), elbow extension (p<0.001, p<0.001), and wrist flexion (p=0.04, p=0.02) compared to TP. Also, dominant shoulder abduction (p=0.04) moment was higher in AR compared to TP. Conclusion: Elderly people probably use a thigh push-off to unload the lower back, but this could also be accomplished with AR. However, AR upper limb loading is higher com- pared to TP. TP is used to unload the lower back and upper limb joints.