Fig. 4. The femoro-tibial joint of the left hind leg of an adult female
Prosarthria teretrirostris. (A) View from the anterior surface. The
anterior semi-lunar process is a thin curved structure forming a dark groove
in the femur. The coverplate is sculpted so that the pivot of a tibial horn
with the incurving part of the anterior semi-lunar process is visible. The
extensor tibiae muscle inserts on the dorsal rim of the tibia and the flexor
tibiae muscle around a ventral U-shaped rim of tibial cuticle. (B) Ventral
view with the tibia extended. The ventral femur has infoldings that form an
internal lump over which the tendon of the flexor tibiae muscle slides (see
Fig. 5B). The membrane
surrounding the tendon is folded to form a pocket. Hair rows on the proximal
tibia can be seen. (C) Dorsal view of the tibia and its articulation with the
femur with the joint flexed. The pivot between the femur and the tibia is seen
as a pair of close appositions between the two semi-lunar processes of the
femur and the horns of the tibia.
