of thigh; broadest above middle of belly; belly narrowed distally,
forming long slender tendon passing lateral to distal part of M.
extensor iliotibialis anticus; bounded anterolaterally by M. vastus
medialis and posterolaterally by Mm. femoritibialis internus and psoas
(proximally).
ORIGIN.--The muscle arises by a short flat tendon from the pectineal
process.
INSERTION.--The long slender tendon enters an elongate channel within
the patellar tendon; the point of entrance is at the proximal end of the
latter tendon just medial to the patella; the tendon passes
distolaterally (within the channel) below the patella and emerges from
the distolateral edge of the patellar tendon and then extends distally
along the anterolateral surface of the head of the fibula, superficial
to the fibular arm of the guide loop for M. extensor iliofibularis, and
joins the anterolateral surface of the common tendon of origin of the
anterolateral heads of Mm. flexor perforatus digiti III, flexor
perforatus digiti IV, and flexor perforatus digiti II; the point of
junction is usually immediately proximal to the proximal end of the
lateral head of M. flexor digitorum longus.
INNERVATION.--The branch of the middle division of the femoral nerve
that supplies M. femoritibialis internus gives off a tiny twig or twigs
that penetrate the lateral surface of the proximal part of M. ambiens.
INDIVIDUAL VARIATION.--None of significance in _T. pallidicinctus_ or in
_P. p. jamesi_; in _T. cupido_ the origin is partly fleshy in one leg.
=_M. Vastus Lateralis_= (M. femoritibialis externus + part of M.
femoritibialis medius), Figs. 14, 16
Fisher and Goodman (1955) apply the name femoritibialis externus to the
muscle unit that I here term the pars postica of M. vastus lateralis.
The reasons for this change are discussed in the section on terminology.
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Thick; on lateral surface of femur
deep to M. extensor iliotibialis lateralis; anterior to M. extensor
iliofibularis and lateral to M. vastus medialis; much of lateral
surface, except proximal part, fused with overlying M. extensor
iliotibialis lateralis; deep surface of anterior half fused with M.
vastus medialis; proximal part overlapping, but usually not fusing with,
insertions of Mm. iliacus and caudofemoralis; partially separable into
two parts--pars lateralis and pars postica, former constituting main
part of muscle; latter considerably smaller and situated deep to
posterodistal part of pars lateralis, except for posterodistal part
extending posterior to edge of pars lateralis; proximal part of pars
postica strongly fused with pars lateralis; posterodistal tendinous edge
of pars lateralis fused or not fused with lateral surface of pars
postica; proximal end (narrow) of pars postica tendinous and variable in
length.
ORIGIN.--_Pars lateralis_: This arises fleshily from most of the lateral
surface and (distally) from the anterior surface of the femur, extending
anteriorly to the anterior intermuscular line, fusing with M. vastus
medialis, and extending posteriorly to the posterolateral intermuscular
line (proximally) and the origin of pars postica (distally); the
proximal end begins at the level of the distal edge of the insertion of
M. iliotrochantericus medius, contacting the insertions of Mm.
iliotrochantericus medius, piriformis, and flexor ischiofemoralis, and
terminates distally at the level of the proximal ends of the femoral
condyles.
_Pars postica_: This arises fleshily and tendinously (proximal end and
deep surface) from the posterolateral surface of approximately the
distal half of the femur, extends posteromedially to the posterolateral
intermuscular line where it contacts the origin of M. femorocruralis,
and extends anteriorly to the level of a line drawn diagonally across
the femur from the proximal end of the origin (at the posterolateral
intermuscular line) to the proximal end of the external condyle; the
distal end is anterior (adjacent) to the attachment of the proximal arm
of the tendinous guide loop for M. extensor iliofibularis; the origin is
adjacent to, but distinct from, the origin of pars lateralis.
INSERTION.--_Pars lateralis_ is fused indistinguishably with M. vastus
medialis; these two muscles form the main (middle) part of the patellar
tendon, which also receives contributions from pars postica and Mm.
femoritibialis internus, extensor iliotibialis lateralis, and extensor
iliotibialis anticus; the patellar tendon attaches to the entire rotular
crest of the tibia; the patella is situated in the proximal part of this
tendon; some deep fleshy fibers of M. vastus lateralis pars lateralis
and M. vastus medialis attach to the proximal edge of the patella. _Pars
postica_ forms a short narrow tendon that fuses to the lateral part of
the tendon of pars lateralis, forming the lateralmost part of the
patellar tendon. A broad flat vinculum extends from the lateral surface
of the femorofibular fascia (defined under M. flexor perforans et
perforatus digiti II) to the deep surface of the lateral part of the
patellar tendon; a similar vinculum extends from the medial surface of
the internal condyle to the deep surface of the medial part of the
patellar tendon.
INNERVATION.--Two or more branches of the middle division of the femoral
nerve penetrate the anterior surface of the fused Mm. vastus lateralis
(pars lateralis) and vastus medialis; short twigs emerge from the deep
surface of pars lateralis and penetrate the superficial surface of the
anteroproximal part of pars postica.
INDIVIDUAL VARIATION.--The proximal ends of M. vastus medialis and M.
vastus lateralis are usually separated by a deep notch. In some legs, a
small bundle of fibers forming the anteroproximal part of M. vastus
lateralis attaches to the lateral surface of M. vastus medialis anterior
to this notch.
_T. cupido_
INDIVIDUAL VARIATION.--One leg shows the same variation found in _T.
pallidicinctus_ (see above). In several legs, pars lateralis does not
extend so far proximally as usual, but begins at the level of insertion
of M. piriformis (does not contact the insertion of M.
iliotrochantericus medius) and may not overlap M. iliacus. In a few
legs, no vincula are associated with the patellar tendon.
_P. p. jamesi_
INDIVIDUAL VARIATION.--Pars lateralis often begins proximally at the
level of the insertion of M. piriformis.
=_M. Vastus Medialis_= (Part of M. femoritibialis medius), Figs. 13, 14,
15
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Thick; on anteromedial surface of
femur medial to anterior part of M. vastus lateralis pars lateralis;
bounded medially by Mm. ambiens and extensor iliotibialis anticus
(distally); bounded posteromedially by M. femoritibialis internus;
proximal part medial to posterior ends of Mm. iliacus,
iliotrochantericus medius, and gluteus profundus; lateral surface,
except proximal part, fused with anterior part of M. vastus lateralis
pars lateralis; part of lateral surface of M. vastus medialis covered by
sheet of fascia attaching to anterior intermuscular line; M. vastus
lateralis separable from this fascia, but fascia absent anteriorly and
distally and these two muscles indistinguishably fused.
ORIGIN.--The proximal third is attached narrowly by its lateral edge;
the distal two thirds is attached broadly by its entire deep surface.
The proximal third arises tendinously from the trochanteric ridge and
the proximal end of the anterior intermuscular line and fleshily from a
narrow area of the femur adjacent (medial) to the latter; the distal
part arises tendinously from the anterior intermuscular line and
fleshily from a broad adjacent area on the anteromedial surface of the
femur, terminating distally at the level of the proximal end of the
internal condyle; the posterior edge contacts the origin of M.
femoritibialis internus.
INSERTION.--Attachment is in common with M. vastus lateralis pars
lateralis, which see.
INNERVATION.--Two or more branches of the middle division of the femoral
nerve penetrate the anterior surface of the fused Mm. vastus medialis
and vastus lateralis pars lateralis; a variable number of branches of
the same division penetrate the medial surface of the proximal part of
M. vastus medialis.
INDIVIDUAL VARIATION.--None of significance in any of the three species
studied.
=_M. Femoritibialis Internus_=, Figs. 13, 15
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Elongate; on posteromedial surface
of femur; bounded anteriorly by M. vastus medialis and posteriorly by M.
adductor profundus (overlapping anterior edge of latter); anteroproximal
part lateral to M. ambiens; anterodistal corner deep to distal end of M.
extensor iliotibialis anticus; distal part of muscle split into
superficial and deep layers; superficial layer thin, narrow, and
tendinous except for proximal end; deep layer wider, much thicker, and
fleshy except for distal end taking form of flat tendon; anterior edge
of latter somewhat fused to medial edge of tendon of M. vastus medialis;
deep layer widest near distal end of fleshy part; posterior edge of
superficial layer fused to underlying deep layer, and anterior edge
fused to (continuous with) posterior edge of tendon of M. extensor
iliotibialis anticus.
ORIGIN.--The origin is mostly fleshy from the posteromedial surface of
the femur between the origin of M. vastus medialis and the posterior
intermuscular line, terminating immediately proximal to the internal
condyle.
INSERTION.--The tendons of both superficial and deep layers attach to
the medial part of the rotular crest, forming the medialmost part of the
patellar tendon.
INNERVATION.--The posteriormost branch of the middle division of the
femoral nerve penetrates the medial surface of the muscle near the
proximal end.
INDIVIDUAL VARIATION.--None of significance in any of the three species
studied.
=_M. Extensor Iliofibularis_= (M. biceps femoris), Figs. 12, 14, 16, 17
The term extensor in the name of this muscle does not refer to its
function. Howell (1938) used the term extensor to indicate derivation of
the muscle from the primitive dorsal extensor muscle mass. (Likewise he
used the term flexor to indicate derivation from the primitive ventral
flexor muscle mass.)
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Deep to M. extensor iliotibialis
lateralis and posterior to femur; broad proximally and narrow distally;
posterior to M. vastus lateralis and anterior to proximal part of M.
flexor cruris lateralis (superficial to distal part of latter);
anteroproximal part aponeurotic, fused to deep surface of aponeurosis of
M. extensor iliotibialis lateralis; proximal part of aponeurosis of M.
extensor iliofibularis also fused to dorsal edges of underlying Mm.
gluteus profundus and piriformis.
ORIGIN.--The posterior part is fleshy from the ventromedial surface of
the entire lateral iliac process; the anterior part is aponeurotic from
the posterior part of the anterior iliac crest.
INSERTION.--The tendon forms along the posterodistal edge of the belly
and continues beyond the end of the belly as a cylindrical tendon that
passes through the tendinous guide loop (the belly terminates
approximately at the level of the guide loop), then extends
anterodistally into the shank musculature; the tendon passes between the
medial and lateral heads of M. flexor perforatus digiti IV, between the
medial and lateral heads of M. flexor perforatus digiti II, lateral to
the common tendon of the anterolateral heads of Mm. flexor perforatus
digiti IV, flexor perforatus digiti II, and flexor perforatus digiti
III, and between the posterior and lateral heads of M. flexor digitorum
longus, attaching to the fibular tubercle.
The tendinous guide loop has three arms--proximal femoral, distal
femoral, and fibular; the proximal and distal femoral arms unite
posterior to the tendon of M. extensor iliofibularis; the proximal arm
is medial to, and the distal arm is lateral to, the latter; the fibular
arm joins the distal edge of the distal arm lateral to the tendon of M.
extensor iliofibularis. The proximal arm extends anteroproximally
lateral to the medial head of M. flexor perforatus digiti IV and medial
to M. vastus lateralis pars postica, attaching to a narrow line on the
anterolateral surface of the femur a short distance proximal to the
external condyle and adjacent (posterior) to the origin of M. vastus
lateralis pars postica. The distal arm extends anteriorly medial to the
posterior head of M. flexor perforans et perforatus digiti II and medial
to M. vastus lateralis pars postica, attaching in common with the tendon
of origin of M. gastrocnemius pars externa to a small oval area on the
posterolateral surface of the femur a short distance proximal to the
fibular groove; the arm is also fused to the underlying articular
capsule. The fibular arm (broadest of the three) passes deep to, and
fused with, the common tendon of origin of the lateral heads of Mm.
flexor perforatus digiti IV and flexor perforatus digiti II, superficial
to the common tendon of origin of the anterolateral heads of Mm. flexor
perforatus digiti IV, flexor perforatus digiti II, and flexor perforatus
digiti III, and deep to the tendon of M. ambiens, attaching broadly to a
narrow line on the anterolateral surface of the proximal part of the
fibula; the arm is also fused to the underlying articular capsule.
INNERVATION.--A branch of the middle peroneal division of the sciatic
nerve sends twigs to the deep surface of the anteroproximal part; the
dorsal peroneal division of the sciatic nerve penetrates the deep
surface of the proximal end.
INDIVIDUAL VARIATION.--In some instances a variable number of twigs
arises from the peroneal nerve near the middle of the thigh and enters
the deep surface of the muscle. They are difficult to expose without
breaking and may have been overlooked in some specimens.
_T. cupido_
INDIVIDUAL VARIATION.--The same variation is found as in _T.
pallidicinctus_ (see above). In one leg, the tendon of insertion
bifurcates into proximal and distal arms before attaching.
_P. p. jamesi_
DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--It arises from the
ventral rather than the ventromedial surface of the lateral iliac
process (there is no ventromedial surface to this process).
INDIVIDUAL VARIATION.--In nearly all of the legs, minute twigs to M.
extensor iliofibularis come off the peroneal nerve near the middle of
the thigh. The insertional tendon tends toward doubleness in two legs.
=_M. Piriformis_= (M. gluteus medius et minimus), Figs. 16, 20H, I
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Small, thin, and triangular; lateral
to antitrochanter and posterior part of trochanter; deep to M. extensor
iliofibularis and posterior (adjacent) to M. gluteus profundus; distal
half (or more) tendinous.
ORIGIN.--The muscle arises fleshily from the posterior end of the
anterior iliac crest (ventral to the origins of Mm. extensor
iliotibialis lateralis and extensor iliofibularis) beginning adjacent to
the posterior end of M. gluteus profundus.
INSERTION.--The flat tendon narrows, overlaps the anteroproximal corner
of insertion of M. flexor ischiofemoralis, and attaches to the lateral
surface of the proximal part of the femur immediately anterior to the
insertion of M. flexor ischiofemoralis and posterior to the proximal end
of M. vastus lateralis; the attachment is posterodistal to the insertion
of M. iliotrochantericus medius and posteroproximal to the insertion of
M. iliacus.
INNERVATION.--The small anterior peroneal division of the sciatic nerve
turns anteriorly immediately after emerging from the ilio-ischiatic
fenestra and passes deep to M. piriformis, giving twigs to the deep
surface.
INDIVIDUAL VARIATION.--In both legs of one specimen, the insertion does
not overlap the insertion of M. flexor ischiofemoralis. The
posteroproximal corner of the muscle is tendinous in one leg.
_T. cupido_
INDIVIDUAL VARIATION.--The anterior border is somewhat fused with the
posterior edge of M. gluteus profundus in one leg, while in another
there is a slight gap between the origins of M. gluteus profundus and M.
piriformis. In one leg, the posterior edge of the origin is aponeurotic.
On both sides of one specimen, an accessory tendinous band arises
several mm. posterior to the main part of M. piriformis and joins the
proximal part of the insertional tendon, thus forming a Y-shaped unit
(fig. 20I); the accessory tendon arises from the anterior end of the
lateral iliac process (left side) or from the anterior part of the
lateral iliac fossa (right side). The insertion may be proximal (rather
than posterior) to the proximal end of M. vastus lateralis. In one leg,
the insertional tendon is partly fused to the insertional tendon of M.
flexor ischiofemoralis.
_P. p. jamesi_
INDIVIDUAL VARIATION.--There is often a gap between the origins of M.
gluteus profundus and M. piriformis. In one leg (fig. 20H), the
posteroproximal corner of the muscle is aponeurotic. The insertion is
often proximal (rather than posterior) to the proximal end of M. vastus
lateralis. In one instance, the insertion does not overlap the insertion
of M. flexor ischiofemoralis.
=_M. Gluteus Profundus_= (M. iliotrochantericus posterior), Figs. 14, 16
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Large and thick; covering
dorsolateral surface of entire preacetabular part of ilium; deep to Mm.
extensor iliotibialis lateralis and extensor iliotibialis anticus;
bounded posteriorly by M. piriformis and ventrally by M. iliacus;
ventral edge fused with anterior part of latter and with proximal
accessory aponeurosis of M. extensor iliotibialis lateralis; tough sheet
of fascia strongly fused to anterior two thirds of lateral surface;
posterior to this, fascia overlying muscle but not attaching to it;
posterior half of fascia fused to overlying aponeurosis of M. extensor
iliotibialis lateralis; deep surface of muscle somewhat fused to
proximal part of M. iliotrochantericus medius.
ORIGIN.--The superficial surface is tendinous from the entire anterior
iliac crest except the posterior end and from the crest forming the
anterior and anterolateral edges of the ilium; the muscle arises
fleshily from the entire dorsolateral surface of the preacetabular ilium
as far posteriorly as the level of the pectineal process; the dorsal
edge is adjacent (anterior) to the origin of M. piriformis.
INSERTION.--The attachment is by a short, wide, thick tendon to a curved
line (convex anteriorly) on the lateral surface of the femoral
trochanter.
INNERVATION.--The anterodorsal division of the femoral nerve turns
dorsally through the femoral notch of the ilium and penetrates the deep
surface of the ventral part of the muscle midway of its length; the
anterior peroneal division of the sciatic nerve passes deep to M.
piriformis and terminates near the posterodorsal edge of M. gluteus
profundus.
INDIVIDUAL VARIATION.--On both sides of one specimen, the branch from
the femoral nerve passes lateral to the extreme anteroproximal corner of
M. iliotrochantericus medius instead of through the femoral notch.
_T. cupido_
INDIVIDUAL VARIATION.--In one leg, the insertional tendon is strongly
fused to the insertional tendon of M. iliotrochantericus medius.
_P. p. jamesi_
INDIVIDUAL VARIATION.--None of significance.
=_M. Iliacus_= (M. iliotrochantericus anterior), Figs. 13, 14, 15, 16,
17
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Adjacent ventrally to ventrolateral
edge of M. gluteus profundus; lateral edge much thicker than medial
edge; deep to M. extensor iliotibialis lateralis and anterolateral to M.
iliotrochantericus medius; distal (posterior) end passing between
proximal ends of Mm. vastus medialis and vastus lateralis pars
lateralis; insertion overlapped by latter; dorsal surface of anterior
part fused with ventrolateral edge of M. gluteus profundus and with
ventral surface of proximal accessory aponeurosis of M. extensor
iliotibialis lateralis; ventral surface partly fused with distal
accessory aponeurosis of latter muscle.
ORIGIN.--The origin is fleshy and tendinous from the lateral edge of the
anterior part of the ilium.
INSERTION.--The attachment is by a short flat tendon to the lateral
surface of the femur distal to the trochanter and anterodistal to the
insertion of M. piriformis and deep to the proximal part of M. vastus
lateralis pars lateralis.
INNERVATION.--The dorsal division of the femoral nerve penetrates the
ventral surface.
INDIVIDUAL VARIATION.--The dorsal division of the femoral nerve may fuse
proximally with either the anterior or middle division. In one leg,
there are two separate branches to the muscle.
_T. cupido_
INDIVIDUAL VARIATION.--The insertion may not be overlapped by M. vastus
lateralis. The dorsal division of the femoral nerve is fused proximally
with the middle division in one leg.
_P. p. jamesi_
DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The fleshy origin is
wider.
INDIVIDUAL VARIATION.--The dorsal division of the femoral nerve may fuse
proximally with either the anterior or middle division. In one leg,
there are two branches to M. iliacus, one fused with the anterior
division and the other with the middle division.
=_M. Iliotrochantericus Medius_=, Figs. 17, 20A, B, C, D
_T. pallidicinctus_
GENERAL DESCRIPTION AND RELATIONS.--Small and triangular; ventral to
posterior half of M. gluteus profundus; all but posteroventral corner
deep to latter; posteromedial to M. iliacus, anterior to neck of femur,
and dorsolateral (adjacent proximally) to M. psoas; proximal end notched
at level of femoral notch for passage of anterodorsal division of
femoral nerve; part anterior to femoral notch mainly tendinous; dorsal
surface of proximal part somewhat fused to M. gluteus profundus,
proximal accessory aponeurosis of M. extensor iliotibialis lateralis
split into two sheets enclosing and fusing with M. iliotrochantericus
medius, ultimately attaching to lateral edge of ilium in common with
origin of latter muscle.
ORIGIN.--The muscle arises from the ventrolateral surface of the ilium
anterior to the acetabulum and posterior to the origin of M. iliacus;
the anterior part attaches to the ventrolateral edge of the ilium and
the posterior part attaches just above the ventral edge. The muscle is
not attached to the concavity of the femoral notch (the origin is
notched here). The part attaching anterior to the femoral notch is
narrow, tendinous, and continuous anteriorly with the accessory
aponeurosis of M. extensor iliotibialis lateralis (thus the anterior
border of the muscle cannot be exactly delimited). The part attaching
posterior to the femoral notch is wider and fleshy (fig. 20A).
INSERTION.--The short flat tendon attaches to the lateral surface of the
distal end of the trochanter slightly anterior and immediately distal to
the insertion of M. gluteus profundus; the attachment is proximal to the
origin of M. vastus lateralis, anteroproximal to the insertion of M.
piriformis, and several mm. proximal to the insertion of M. iliacus.
INNERVATION.--The small posterodorsal division of the femoral nerve
penetrates the ventral surface.
INDIVIDUAL VARIATION.--On both sides of one specimen, the femoral notch
is absent and the proximal end of the muscle is not notched; the
proximal part is entirely fleshy and the anterior border is well defined
(fig. 20D).
_T. cupido_