Fig. 1. Anatomy of the femoro-tibial joint of a left hind leg of a mature locust. (A) Photograph of the anterior (=lateral) surface. The semi-lunar processes and the proximal part of the tibia are black and heavily sclerotised. The curved horns of the tibia are engaged in the domes of the more lightly sclerotised ventral parts of the semi-lunar processes. (B) End-on photograph with the tibia held at an angle of approximately 90° relative to the femur. The hinge apposition of the flat surfaces of the two semi-lunar processes and the horns of the tibia are shown. (C,D) Drawings of the femoro-tibial joint. (C) Anterior surface with the tibia flexed about the femur. The anterior cover plate is drawn as though transparent to show a tibial horn engaged in the ventral dome of a semi-lunar process. The extent of the inwardly projecting process from the ventral wall of the femur, Heitler’s lump, and the plane of weakness about which the tibia bends are indicated by dashed lines. (D) Ventral view of the distal femur and proximal tibia with the joint membrane and muscles removed to show the invaginations of the semi-lunar processes. The tendon of the extensor tibiae inserts on the dorsal wall of the tibia and that of the flexor, after splitting into two, on the ventral wall. The opposing surfaces of the femur and tibia that form the hinge joint are indicated by the curved arrows.
