M. Extensor Iliotibialis Lateralis (M. iliotibialis), [Figs. 12], [13], [20]F, G
T. pallidicinctus
Fig. 13. Tympanuchus pallidicinctus 2L. Medial view of the superficial muscles of the left leg. × 1. Articular capsule shown by concentrically arranged dashes.
General Description and Relations.—Most superficial muscle on lateral surface of thigh; broad, flat, and triangular; bounded anteriorly by M. extensor iliotibialis anticus and posteriorly by M. flexor cruris lateralis; posterior part considerably thicker than anterior part; anteroproximal and centrodistal parts aponeurotic; extreme posteroproximal corner also aponeurotic (could be considered tough sheet of connective tissue intimately fused with M. extensor iliotibialis lateralis, rather than part of muscle itself; see [Fig. 20]F); latter aponeurosis, as well as adjacent fleshy fibers, overlapped by M. flexor cruris lateralis; this aponeurosis fused with posterior end of underlying M. caudofemoralis pars iliofemoralis; centrodistal aponeurosis tightly fused to underlying Mm. vastus lateralis and vastus medialis; fleshy fibers posterior to this aponeurosis also fused with M. vastus lateralis, although posterior third of muscle free; fleshy part anterior to this aponeurosis bound by tough connective tissue to underlying M. vastus medialis, although no fusion of fibers; anterior edge tightly bound by strong connective tissue to M. extensor iliotibialis anticus, with some fusion of fibers (proximally); posteroproximal corner bound by tough connective tissue to adjacent muscles; anteroproximal aponeurosis fused with aponeurotic anteroproximal part of underlying M. extensor iliofibularis. Continuous proximal aponeurosis of M. extensor iliotibialis anticus and of M. extensor iliotibialis lateralis underlain by tough fascial sheet overlying M. gluteus profundus; anterior part of this fascia tightly fused to latter muscle but free from overlying aponeurosis; posterior part of this fascia tightly fused to overlying aponeurosis but free from M. gluteus profundus; middle part of fascia fused to both aponeurosis and M. gluteus profundus.