Abstract: A strut component for an orthosis, especially a knee orthosis, takes the form of a deformed ductile metallic tube containing uncured plastics and fibre composite material. The tube has a cross-section which is much longer than its width and with parallel sides, and the composite core is a close-fit within the tube, the internal cross-sectional area of the tube being no more than Kc2 where c is the internal circumference of the tube and k is a number less than or equal to 0.1. When the orthosis is constructed, the strut is shaped to suit the limb to be supported and heated to cure the composite core.