Sem 2 RA Week 3 Flashcards
Muscle compartments of the thigh?
Anterior (largest)
Medial
Posterior
Muscle compartments of the thigh separated by?
Thick bands of connective tissue called intermuscular septae
Muscle compartments of the thigh function?
Anterior compartment = flex hip, extend knee
Medial compartment = adduct hip
Posterior compartment = extend hip, flex knee
Bony features of femur?
small indent in head called fovea
intertrochanteric line connects G+L trochanter on anterior surface (posterior = intertrochanteric crest)
anterior shaft = featureless (due to v little muscle attachment)
posterior shaft = pronounced bony ridge called linea apsera, becomes pectineal line proximally and supracondylar lines distally
anteriorly = patellar surface
posteriorly = medal + lateral condyles, just above condyles on either side are epicondyles
on medial epicondyle = adductor tubercle
what is found on medial epicondyle?
Adductor tubercle
Muscles of anterior thigh?
Hip flexors
- iliacus
- psoas major
- pectineus
- sartorius
Knee extensors i.e. quadriceps (4 heads)
- rectus femoris
- vastus medialis
- vastus lateralis
- vastus intermedius
Hip flexors of anterior compartment?
i.e. attachments, innervation, function
Iliopsoas → Iliacus
- iliac crest, iliac fossa, ala of sacrum, ant. sacroiliac ligament → passes over anterior surface of iliac bone → passes deep to inguinal ligament → unites with tendon of psoas major to insert into lesser trochanter
- innervation = femoral nerve (L2, 3)
- function = flex hip
Iliopsoas → Psoas major
- T12-L5 VB + IV discs, lumbar transverse processes → deep to inguinal ligament with iliacus → lesser trochanter
- anterior rami L1-3
- flex hip
Pectineus
- superior ramus of pubis → pectineal line of femur
- femoral nerve (L2, 3)
- adduct + flex hip, assists with medial rotation (ant. compartment muscle but has some functions of medial comp, also occasionally inv. by obturator nerve)
Sartorius
- ASIS → superior medial surface of tibia (see how it passes over knee joint)
- femoral nerve (L2, 3)
- flex, abduct, laterally rotate hip, flex knee (i.e. sitting cross-legged)
(in pic inguinal ligament has been removed)
…
Knee extensors of anterior compartment?
Attachments, innervation, function
Quadriceps
Rectus femoris (most superficial)
- diff from rest of quads - attaches to AIIS + ilium above acetabulum
- so not only acts at knee joint but also produces hip flexion
Vastus lateralis
- greater trochanter + lat. linea aspera
Vastus medialis
- intertrochanteric line + med. linea aspera
Vastus intermedius
- ant. + lat. shaft of femur
common distal attachment = quadriceps tendon then tibial tuberosity via patellar ligament
innervation = femoral nerve (L2, 3, 4)
Action = extend knee (rectus fem. also flexes hip)
black arrow = quadriceps tendon
red rod = patellar ligament
green arrow = tibial tuberosity (distal attachment of quads)
vastus medialis also plays an important role in holding patella in place i.e. helps prevent patellar dislocation
Femoral nerve pathway anterior thigh?
branches?
terminal cutaneous branch?
what is special about this nerve?
From lumbar plexus (L2, 3, 4) → passes deep to inguinal ligament → medial to ASIS → runs on tendon of iliopsoas
once enters ant. comp of thigh - will branch
- muscular branches = ant. thigh
- articular branches = hip and knee
- cutaneous branches = anteromedial thigh
Saphenous nerve is terminal cutaneous branch - anteromedial knee, leg + foot
- only nerve that innervates below level of knee joint that is NOT derived from sciatic nerve
femoral artery + vein surrounded by femoral sheath
Muscles of medial thigh?
Function?
Hip adductors
- Gracilis
- Adductor longus
- Adductor breis
- Adductor magnus
- Obturator externus (not NOT adduct hip but is still part of medial compartment)
…
Gracilis compartment?
Attachments?
Innervation?
Function?
Medial = hip adductor
attach = body + inf. ramus of pubis → superior medial surface tibia
innervation = obturator (L2, 3)
Function = adducts hip, flexes knee
(very close to attachment of sartorius + semitendonosus i.e. goose’s foot)
Adductor longus compartment?
Attachment?
Innervation?
Function?
medial compartment = hip adductor
attach = body of pubis → middle ⅓ linea aspera
innervation = obturator (L2, 3, 4)
Function = adducts thigh
Adductor brevis comp?
attachments?
Innervation?
Function?
Immediately deep to adductor longus
medial comp = hip adductor
attach = body + inf. ramus of pubis → pectineal line + proximal linea aspera
innervation = obturator (L2, 3, 4)
Function = adducts thigh (may assist flexion)
Adductor magnus comp?
Attachments?
Innervation?
Function?
Medial compartment = hip adductor
attachments = ischiopubic ramus + ischial tuberosity → linea aspera, med. supracondylar line, adductor tubercle
Innervation = obturator (L2, 3, 4)
- hamstring part = tibial division of sciatic nerve
function = adducts thigh → adductor part flexes + hamstring part extends thigh
(note gap between part that attaches to supracondylar line + part that attaches to adductor tubercle = adductor hiatus)
Obturator externus comp?
Attachment?
Innervation?
Function?
Medial compartment
attach = margins of obturator foramen + obturator membrane → trochanteric fossa (indent in greater trochanter)
innervation = obturator nerve (L3, 4)
function = lateral rotates thigh
NOTE - in adductor compartment but NOT an adductor!!
Obturator nerve pathway medial compartment?
Branches?
L2, L3, L4 anterior divisions → runs along lateral wall of pelvis → to obturator canal
as enters medial thigh, divides into anterior + posterior branches (relative to adductor brevis i.e. anterior branch anterior surface, posterior branch deep)
anterior branch = cutaneous to middle part of medial thigh
muscular branches to medial thigh (pic - pale is anterior branch, dark is posterior branch)
see anterior branch with relationship to adductor brevis
can see deep branch diappearing behind adducto rbrevis
adductor canal found?
Runs from?
Landmark?
Boundaries?
Contents?
Distal part of thigh between anterior + posterior compartments
Apex of femoral triangle → adductor hiatus
Found deep to distal half of sartorius muscle
Boundaries = sartorius (roof), vastus medialis (medial), adductor longus (floor)
Contents = femoral vessels, branches of femoral nerve, saphenous nerve (to reach anteromedial aspect of knee)
Adductor canal contents?
Femoral vessels - pass through adductor hiatus to reach popliteal fossa
Saphenous nerve = passes between sartorius + gracilis to supply skin of anteromedial knee, leg + foot (does not go through adductor hiatus)
Arterial supply to anterior + medial thigh?
pathway?
Function?
Femoral artery (cont. of ext. iliac)
- femoral triangle (deep to ing. lig) → adductor canal → adductor hiatus to become popliteal artery
- supplies anterior + anteromedial thigh
Femoral artery gives off profunda femoris branch
- deep to adductor longus → 3-4 perforating branches through adductor magnus
- medial + lateral circumflex branches
Obturator artery (from int. iliac)
- through obturator foramen to medial compartment → ant. and post. branches
- anterior branch = muscles of medial comp
- Posterior branch = muscles attached to ischial tuberosity (post. compartment)
External iliac changes name to femoral once passes deep to inguinal ligament → continues towarda adductor hiatus
profunda femoris - can see perforating branches + lateral and medial circumflex
important anastamosis (cruciate) - posterior to proximal end of femur, involves med + lat circumflex femoral arteries, perfroarting branch from PF, inf. gluteal artery
presence of inf. gluteal (int. iliac) means alternative route for bloodflow into thigh if blockage in proximal part of femoral artery
great saphenous vein empties into femoral vein (so does superficial epigastric)
Hip bone compromised of?
Features? (medial)
what separates greater + lesser sciatic notch?
3 bones = ilium, pubis, ischium
ischial spine separates greater + lesser sciatic notch
features of hip bone (lateral)
greater sciatic notch will form part of greater sciatic foramen in conjunction with sacrotuberous + sacrospinous ligament
Anatomical position of femur?
what do these angles mean?
pronounced angle between shaft of femur + head&neck of femur = angle of inclincation
angle means distal end of femur is located more medially from the proximal end - important for position of knee joint relative to the hip joint
angle of anteversion (torsion) - best be seen by viewing femur from superior position. Long axis of head+neck of femur is not in line with axis that runs through distal condyles of femur → angle between 2 lines called angle of torsion
has implications for muscle attachment + movements
bony features of femur?
indent = fovea
connecting greater + lesser trochanter = intertrochanteric line
Muscles of gluteal region?
Support?
gluteus maximus?
Attachments?
function?
Innervation?
most superficial muscle in gluteal region
sacrum, sacrotuberous ligament + ileum behind posterior gluteal line → iliotibial tract (¾) and gluteal tuberosity of femur (¼)
function = extends hip, assists lateral rotation
Innervation = inferior gluteal nerve (L5, S1, S2)
tensor fascia latae attachments?
functions?
Innervation?
ASIS and anterior iliac crest → iliotibial tract
function = tenses fascia latae and iliotibial tract + supports femur on tibia during standing
innervation = superior gluteal nerve (L4, L5, S1)
inferior gluteal nerve pic B (once glut max reflected)
gluteus medius?
attachments?
function?
innervation?
deep to gluteus maximus
ilium between posterior + anterior gluteal lines → greater trochanter of femur (lateral surface)
function = abducts and medially rotates hip
innervation = superior gluteal nerve (L4, L5, S1)
gluteus minimus?
attachments?
function?
Innervation?
just deep to gluteus medius
ilium between anterior and inferior gluteal lines → greater trochanter of femur (anterior surface)
function = abducts + medially rotates hip
Innervation = superior gluteal nerve (L4, L5, S1)
piriformis attachment?
passes?
Function?
Innervation?
anterior sacrum + sacrotuberous ligament → greater trochanter of femur (superior border)
passes through greater sciatic foramen
function = laterally rotates hip
innervation = anterior rami S1, S2
obturator internus attachment?
Passes?
function?
Innervation?
pelvic surface of obturator membrane → medial side of greater trochanter (trochanteric fossa)
passes through lesser sciatic foramen
function = laterally rotates hip
innervation = nerve to obturator internus (L5, S1)
gemelli attachments?
function?
Innervation?
superior = ischial spine
inferior = ischial tuberosity
→ blend with tendon of obturator internus
function = laterally rotate hip
superior = nerve to obturator internus
inferior = nerve to quadratus femoris
orange arrow = course of OI as it passes through lesser sciatic foramen, will lie in between superior + inferior gemelli muscles
black arrow = tendon of OI
quadratus femoris attachments?
function?
innervation?
ischial tuberosity → quadrate tubercle on intertrochaneric crest of femur
function = laterally rotates hip
innervation = nerve to quadratus femoris (L5, S1)
obturator externus attachments?
function?
innervation?
outer surface of obturator membrane → passes posterior to neck of femur → trochanteric fossa on medial side of greater trochanter
function = laterally rotates hip
innervation = obturator nerve (L3, L4)
gluteus medius + minimus attaching on anterior + lateral parts of greater trochanter = produce medial rotation + abduction
sciatic nerve roots?
branches pathway?
L4 - S3
tibial leaves below piriformis
common peroneal may leave below, above or through piriformis
gluteal nerves and vessels?
divisions?
pathway?
pic
superior emerge superior to piriformis and vice versa
superior nerves + vessels divide into superficial + deep branches
Deep branch courses anteriorly in plane between gluteus medius + minimus
deep branch of nerve terminates by suplying tensor fascia latae
…
posterior cutaneous nerve of thigh found?
roots?
supplies?
lies on posterior aspect of sciatic nerve
S1, S2, S3
supplies skin of posterior thigh but also gives inferior clunial nerves to skin of inferior half of buttock
middle clunical = posterior aspect of sacrum
superior = superior half of buttock
posterior = inferior half of buttock + posterior thigh
ligament attaching to fovea = attaches to floor of acetabulum
capsule attachment hip joint?
hip bone = capsule follows margins of articular surface
on femur - capsule does not attach around articular margin, instead attaches along margin of neck of femur
what is this ligament?
attachments?
function?
iliofemoral ligament (upper + lower bands)
AIIS → intertrochanteric line
function = limits extension, lat rotation, adduction (upper), abduction (lower)
extnded = taut
flexed = relaxed
what ligament is this?
attachments?
Function?
pubofemoral
iliopubic eminence → lower part of intertrochanteric line
function = limits extension, lat rotation + abduction
what ligament is this?
attachments?
Function?
ischiofemoral (lies posteriorly)
posterior aspect of acetabulum → greater trochanter
function = limits extension, medial rotation, adduction
blood supply to hip joint?
artery of head of femur (travels in ligament of head of femur) - it is a branch of obturator artery
medial + lateral circumflex arteries - branches of profunda femoris in anterior thigh
what muscle is this?
attachment?
innervation?
semitendinosus (located in medial aspect of posterior compartment)
ischial tuberosity → medial surface of superior tibia
innervation = tibial division of sciatic (L5, S1, S2)
note long tendon hence name
what muscle is this?
attachment?
innervation?
semimembranosus
ischial tuberosity → posterior surface of medial condyle of tibia
innervation = tibial division of sciatic (L5, S1, S2)
what muscle is this?
attachment?
innervation?
biceps femoris
long head = ischial tiberosity
short head = linea aspera + lateral supracondylar line of femur
→ head of fibula
long head = tibial division of sciatic (L5, S1, S2)
short head = common peroneal division of sciatic (L5, S1, S2)
red + yellow arrows = semitendinosus
rotation of knee?
sciatic nerve roots?
found?
divisions?
L4-S3
deep to long head of biceps femoris
divisions = tibial + common peroneal divisions
popliteal fossa roof?
pierced by?
roof = deep fascia
pierced by:
- sural nerve (supplies cutaneous innervation to leg + foot)
- short saphenous vein
boundaries of popliteal fossa?
superior = diverging tendons of hamstrings
- biceps femoris laterally
- semimembranosus + semitendinosus medially
inferior = medial and lateral heads of gastrocnemius
popliteal fossa contents?
popliteal artery
popliteal vein
terminal branches of sciatic = tibial nerve + common peroneal nerve
…
floor of popliteal fossa?
popliteal surface of femur
capsule of knee joint
popliteus muscle
features of knee joint capsule of floor of popliteal fossa?
pic
middle genicular artery is branch of popliteal artery, pierces through knee joint capsule to supply cruciate ligaments (accompanied by middle genicular vein)
popliteal artery?
pathway?
branches?
continuation of femoral artery
Adductor hiatus (name change femoral to popliteal) → inferior border of popliteus
5 genicular branches: middle (cruciate ligaments), medial + lateral superior, medial + lateral inferior
terminal branches = anterior tibial + posterior tibial artery
pic A - next to tibial nerve is common peroneal
arrows = genicular arteries (med + lat sup + inf)
Photograph A shows the anterior compartment of the thigh. Sartorius originates from the anterior superior iliac spine (ASIS) and crosses the anterior compartment from lateral to medial to insert at the medial side of the knee.
Photograph B shows the medial side of the knee, where sartorius is the most superior muscle to attach to this area of the tibia.
The femoral artery, vein and the saphenous branch of the femoral nerve descend the anterior compartment of the thigh inferior to sartorius in the sub-sartorial (adductor) canal.
Sartorius acts to flex, abduct and laterally rotate the hip joint; it also acts to flex and medially rotate the knee joint.
Photograph A shows the anterior surface of the thigh. Rectus femoris is part of the quadriceps muscle group that extends the knee. Rectus femoris attaches to the anterior inferior iliac spine then descends the thigh to attach to form part of the quadriceps tendon, it therefore passes over the anterior surface of the hip joint and will also flex the hip joint.
Photograph B shows the quadriceps tendon as it passes over the surface of the patella. The patella is a large sesamoid bone that forms inside the quadriceps tendon in response to the stresses on the tendon due to movement of the knee joint.
The other quadriceps muscles are the vastii. Photograph A shows vastus intermedius that lies inferior to rectus femoris. Photograph B shows vastus lateralis and vastus medialis. Note that vastus medialis has more distal muscle fibres than vastus lateralis, a feature that is thought to help prevent dislocation of the patella. All of the vastii appear to form one large sheet of muscle. All of the quadriceps muscles help to form the quadriceps tendon, so all of the muscles can extend the knee joint. The vastii muscles originate from the femur so do not cross the hip joint and cannot act upon it. Photograph C shows the quadriceps tendon passing over the patella to form the patellar tendon that attaches to the tibia.
You may have noticed that the hip joint follows the general rules of movement you have seen in the rest of the body so far –if a muscle crosses the anterior surface of a joint it flexes it, if it crosses the posterior surface of a joint it extends it. Due to the embryological rotation of the lower limb, the opposite happens at the knee joint. For example, the quadriceps muscles cross the anterior surface of the knee joint and they extend the knee; the hamstrings cross the posterior surface and they flex the knee.
You have already seen pectineus and iliopsoas forming the floor of the femoral triangle. Iliopsoas originates as psoas from the lumbar vertebrae and iliacus from the iliac fossa, it inserts into the inferior trochanter of the femur and acts to flex the hip joint. Pectineus originates from the superior pubic rami and inserts into the linea aspera of the femur, it also acts to flex the hip.
These muscles (and obturator externus) are odd ones out in the anterior compartment as they are either not supplied by the femoral nerve or are only partially supplied by the femoral nerve. Iliopsoas is innervated by the femoral nerve (iliacus part) but also by direct branches of the lumbar ventral rami (psoas part). Pectineus may be innervated by the femoral nerve, the obturator nerve or a combination of both nerves depending on the individual.
Obturator externus lies deep in the anterior compartment and is the counterpart of obturator internus on the inner surface of the obturator membrane. It attaches to the greater trochanter of the femur and laterally rotates the hip. It is innervated by the obturator nerve, as this nerve pierces through obturator externus on its way to the medial compartment of the thigh.
The femoral artery is a direct continuation of the external iliac artery as it passes under the inguinal ligament to enter the femoral triangle. It terminates as the popliteal artery posterior to the knee in the popliteal fossa. It divides to form small branches (circumflex iliac and external pudendal are shown) but its main branches supply the thigh itself. Photograph A shows the femoral artery branching to form a profunda femoris (or deep femoral) artery that will form medial and lateral circumflex branches and many muscular branches. The rest of the artery passes down the anterior compartment in the sub-sartorial canal and then passes through the adductor hiatus to reach the popliteal fossa.
Photograph B shows the femoral vein which is a continuation of the popliteal vein. It passes through the adductor hiatus and into the sub-sartorial canal before ascending to the femoral triangle where it is joined by the great saphenous vein.
The femoral nerve is the main nerve supply of the anterior compartment supplying the quadriceps muscles, sartorius, iliacus and often pectineus. It also provides sensory innervation to the anterior surface of the thigh and also to the medial side of the leg via its saphenous branch. Photograph A shows the femoral nerve lying outside the femoral sheath that covers the femoral artery and vein. Photograph B shows the femoral nerve dividing into many branches to supply the anterior compartment.
Photograph A shows the medial compartment of the thigh – this is also called the adductor compartment as all of the muscles adduct the hip joint. The most medial muscle is gracilis – named due to its delicate gracile shape. It inserts into the medial side of the knee, but is the most inferior muscle to do so – this is shown in photograph B. All of the adductors are innervated by the obturator nerve.
Photograph A shows adductor longus. You have seen adductor longus forming the medial border of the femoral triangle. Adductor longus attaches to the pubic bone and the linea aspera of the femur. Photograph B shows adductor brevis, which as its name suggests is shorter that adductor longus. It attaches to the inferior ramus of the pubic bone and the linea aspera.
The largest adductor of the thigh at the hip is adductor magnus. It is so large it attaches to the inferior ramus of the pubic bone and also the ischial tuberosity. The hamstring muscles of the posterior compartment also attach to the ischial tuberosity, so this part of adductor magnus may be called the ‘hamstring part’. This part of adductor magnus can act to extend the hip.
Adductor magnus attaches to the linea aspera but also to the adductor tubercle, this creates an adductor hiatus that allows the passage of the femoral artery and vein into/ and out of the popliteal fossa.
Adductor magnus is innervated by the obturator nerve but the hamstring part is innervated by the sciatic nerve.
The obturator nerve is the main nerve of the medial compartment of the thigh. The nerve exits the obturator foramen to reach the medial compartment where it divides into an anterior (superficial) and posterior (deep) branch. Photograph A shows the anterior division that supplies adductor longus, adductor brevis and gracilis. Photograph B shows the posterior division that supplies obturator externus and adductor magnus.
This slide shows the lateral compartment of the thigh. The fascia of the thigh is called the fasciae latae and is thickened laterally to form the iliotibial tract which passes down the length of the lateral border of the thigh to blend with the fascia of the knee. Enclosed within the upper medial part of the iliotibial tract is a small muscle called the tensor fasciae latae, which is innervated by the superior gluteal nerve.
Photograph A shows the posterior compartment of the thigh of a left thigh with the skin removed to show the thick fascia that covers the hamstring muscles. All of the hamstrings attach to the ischial tuberosity and all act to extend the hip joint and flex the knee joint.
Photograph B shows the fat and fascia removed to reveal the hamstring muscles. Biceps femoris is the most lateral muscle. Biceps femoris has two heads as its name suggests. Photograph C shows the long head that originates at the ischial tuberosity and the short head that originates from the linea aspera and lateral supracondylar ridge of the femur. Both heads unite to insert into the fibula.
All of the hamstring muscles are innervated by the tibial division of the sciatic nerve except the short head of biceps femoris which is supplied by the common peroneal division of the sciatic nerve.
Photographs A and B show the two remaining hamstring muscles – semitendinosus and semimembranosus. Semitendinosus (photograph A) forms a long tendon as it approaches the knee joint; semimembranosus (photograph B) forms a flatter tendon that is more muscular as it approaches the knee. Both muscles insert into the medial side of the tibia. There are 4 muscles that insert here – photograph C shows the arrangement of tendons, with semimembranosus lying under semitendinosus (labelled SM).
In the posterior compartment, the sciatic nerve descends towards the knee and divides to form the common peroneal (lateral) and tibial nerves (medial). Between them, these nerves will form branches that supply all of the muscles of the leg and foot. The division of the sciatic nerve may be at any point between the gluteal region and just superior to the popliteal fossa. The common pattern is seen in photograph A.
Photograph B shows the structures in the roof of the popliteal fossa. The fossa is the anatomical space posterior to the knee joint and contains vessels and nerves that supply the leg. The roof is formed from skin and fascia. Running in the fascia is the sural nerve, which may branch from the tibial nerve or the common peroneal nerve or a combination of both nerves. This is a cutaneous nerve that supplies the posterior surface of the calf and lateral side of the foot. Also present in the fascia is the short saphenous vein that drains the lateral side of the dorsum of the foot, the posterior surface of the calf and then joins the popliteal vein in the popliteal fossa.
Photograph A shows a left knee with the skin and fascia removed to show the boundaries of the popliteal fossa. The superior boundaries are formed by biceps femoris (lateral) and semitendinosus and semimembranosus (medial). The inferior boundaries are also muscular and are formed by the medial and lateral heads of gastrocnemius. Gastrocnemius is a muscle of the posterior compartment of the leg (this compartment is also called the calf).
Photographs A and B show the contents of the popliteal fossa in a right knee. The popliteal vein and the tibial nerve run through the middle of the fossa. The common peroneal nerve crosses the lateral side as it passes towards the head of the fibula. The popliteal artery also passes through the fossa but this is deep in the fossa and cannot be seen at the level of dissection shown in the photographs on this slide.
Photograph A shows the tibial nerve, popliteal vein and popliteal artery in the fossa. Note that the artery is deeper and has a thicker, more rounded wall than the vein. The tibial nerve is flatter and has small pink/purple stripes along its length (an artifact of the embalming process).
Photograph B shows a deep dissection of the fossa. The popliteal artery will form the anterior and posterior tibial arteries that supply the leg and foot. In the popliteal fossa it branches to form five genicular arteries. Four are shown in the photograph – the superior medial (SMG), the superior lateral (SLG), the inferior medial (IMG) and the inferior lateral (ILG). The middle genicular artery is not shown as this runs deep into the capsule.
Popliteus muscle lies deep in the popliteal fossa and forms part of the floor of the fossa. Photograph A shows popliteus with the contents of the fossa intact and photograph B shows popliteus when the contents have been reflected. Popliteus passes between the lateral surface of the lateral condyle of the femur and the shaft of the femur above the soleal line. It is innervated by the tibial nerve and acts to unlock the knee.
Photograph A shows the left gluteal region with the skin removed to reveal the fat and superficial fascia that covers the gluteal muscles. Photograph B shows the same cadaver with the fat and fascia removed to reveal gluteus maximus – the largest and most superficial of the gluteal muscles. Gluteus maximus attaches to the ilium and sacrum and inserts into the iliotibial tract (some fibres pass to the gluteal tuberosity of the femur). Gluteus maximus is a powerful extensor of the hip and is innervated by the inferior gluteal nerve. Photograph C shows gluteus maximus partially reflected to uncover the inferior gluteal nerve (and vessels) that lie in the fascial plane between the gluteal muscles and pierce the deep surface of gluteus maximus.
Gluteus maximus can vary in size between individuals – it is easy to split the muscle as you reflect it. You may find it helpful to pass your fingers under gluteus maximus to find the fascial plane between it and gluteus medius before you begin to section the muscle.
Photograph A shows gluteus maximus completely reflected to reveal gluteus medius. The fat and fascia between the two muscles has also been removed. Gluteus medius originates between the posterior and middle gluteal lines of the ilium and inserts into the greater trochanter of the femur. Photograph B shows gluteus medius reflected and the fat and fascia removed to reveal gluteus minimus. The superior gluteal nerves and vessels lie in the fascial plane between gluteus medius and minimus. Gluteus minimus originates between the middle and inferior gluteal lines of the ilium and inserts into the greater trochanter of the femur.
Both gluteus medius and minimus act to abduct and medially rotate the thigh and are innervated by the superior gluteal nerve.
There are several small lateral rotators of the hip deep in the gluteal region. Photograph A shows piriformis. Piriformis originates from the sacrum inside the pelvis and then passes through the greater sciatic foramen to reach the greater trochanter of the femur. It acts to laterally rotate the hip and is innervated by the nerve to piriformis. It is a good landmark structure, the sciatic nerve passes into the gluteal region from beneath piriformis (as shown in photograph A).
Photograph B shows that piriformis can also be used to identify the superior and inferior gluteal vessels and nerves, as they pass into the gluteal region superior and inferior to piriformis.
Photograph A shows the tendon of obturator internus. The muscle lies on the internal surface of the obturator membrane but the tendon passes through the lesser sciatic foramen to insert into the greater trochanter of the femur. If you observe the tendon carefully you can see a small muscle immediately above it and a small muscle immediately below it. These are the gemelli muscles – superior gemellus from the ischial spine and inferior gemellus from the ischial tuberosity. Both muscles insert with the tendon of obturator internus into the greater trochanter of the femur. All three muscles act to laterally rotate the hip. Obturator internus is supplied by the nerve to obturator internus – this nerve usually also supplies the superior gemellus muscle.
Photograph B shows quadratus femoris (shown by the red plastic strip). It arises from the ischial tuberosity and inserts into the intertrochanteric crest of the femur. It also laterally rotates the hip and is innervated by the nerve to quadratus femoris which usually also innervates the inferior gemellus muscle.
