The forces and moments in the shaft of a distal femoral replacement were measured by telemetry for a subject during different activities, and calculations were then made of the forces at the knee. The axial force showed a small peak at heel-strike followed by two main peaks during stance. In level walking, the peak axial force was between 1,487 and 1,718 N (2.2-2.5 BW), the peak shear force was 269-368 N (0.4-0.54 BW) directed anteriorly on the tibia, the peak axial torque was 7 Nm internal, while the patellofemoral force was 466-571 N. The highest axial force was recorded for descending stairs (2.8 BW). Standing on one leg produced 2.4 BW, while lying supine and raising the leg produced 1.7 BW. The data produced may resemble that of a normal subject, and has application to basic joint mechanics, to joint reconstruction, and to total knee replacement design and evaluation.