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Mohammad Ashraf

Abdulrahman Al-Hanbali

Ahmad Salman

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Structures under the cover of Gluteus Maximus:

1-Bones: Ileum, Femur (Head, greater trochanter and gluteal

tuberosity), Ischium (ischial tuberosity).

2- Ligaments: Sacrotuberous ligament and Sacrospinous ligament.

3- Muscles: gluteus medius, gluteus minimus, lateral rotators:

(Piriformis, Obturator Internus, Superior & Inferior Gemellus,

Quadratus Femoris).

4- Vessels: Superior & Inferior Gluteal Vessels (go through greater

sciatic foramen), Internal pudendal vessels.

5- Nerves: Sciatic nerve, Posterior cutaneous nerve of the thigh, Nerve

to Obturator internus, Nerve to Quadratous, Superior & Inferior

Gluteal nerves, Pudendal nerve.

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Clinical application: *Sciatic nerve goes through greater sciatic foramen

under the Piriformis muscle.

This is important to know when giving intramuscular injection, and we

already know how to divide the gluteal region into 4 parts. So according

to the picture below we give injection in the upper lateral part to be far

from the sciatic nerve, so we don’t damage it, since it’s so important and

supplies too many muscles.

Another way to determine the injection site is by putting your thumb on

the posterior superior spine, hand on iliac crest and stretch your hand

then inject right below your hand.

*This injection is given mainly in the gluteus medius (safer because it’s

far from sciatic nerve), sometimes given in the g. maximus because it’s

bigger and has more vessels (less safe because it’s closer to sciatic n.).

Posterior compartment of the thigh

Muscles: 1- Biceps Femoris (Short & long heads). 2-Semitendinosus. 3-

Semimembranosus. 4- Hamstring (or ischial) part of Adductor

Magnus.

Nerve Supply: ALL supplied by Sciatic nerve.

*Sciatic nerve divides into 2 nerves: Tibial nerve & Common peroneal

(fibular) nerve.

All 4 previous muscles are supplied by Tibial nerve, EXCEPT short head of

biceps femoris which is supplied by common fibular nerve.

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*Make a connection in your mind between the position of the biceps

femoris which is lateral and the position of common fibular nerve which

is also lateral, and because of that part of the biceps (short head) is

supplied by this nerve.

Origin: All muscles originate from Ischial

tuberosity, EXCEPT short head of biceps

femoris (because it’s short, it originates

from the lateral supracondylar line on

the femur).

Insertion: 1- Biceps femoris: Inserts on

the fibula (head/styloid process).

2- Semitendinosus: Inserts on SGS

(upper part of medial surface of tibial

head).

3- Semimembranosus: Inserts on the

posterior part of medial condyle of the

tibia.

4- Adductor magnus: Inserts on

adductor tubercle on the femur.

Action: All of them cross 2 joints: hip joint and

knee joint. So, the action for these muscles will

be flexion of the knee & extension of the hip.

EXCEPT 2 muscles: Short head of biceps femoris

& adductor magnus.

Short head only crosses the knee joint, so it only

helps with flexing the knee.

Adductor magnus only crosses hip joint so the

hamstring part helps with extension of the hip.

In addition to that, medial muscles

(Semitendinosus & semimembranosus) do medial

rotation of the leg, and biceps femoris do lateral

rotation.

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Ischial tuberosity

Ischial tuberosity divides into 2 parts: upper & lower parts, and every

part divids into another 2 parts.

^Origins of ischial tuberosity-originated muscles that mentioned in the

picture are important.

Lower triangular (medial) part has no muscles, but it has subcutaneous

bursa (a sac contains synovial fluid) and when we sit we sit on it, so it

helps in preventing direct connection

between the bone and the skin when

sitting.

Sciatic Nerve

Originates from the sacral plexus (L4, L5, S1,

S2, S3).

Course: From sacral plexus to greater sciatic

foramen (below the piriformis), then goes to

the middle of the thigh, there, gives 2

branches: common peroneal and tibial

nerve. Sciatic nerve gives its branches in

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different sites from person to another.

You can determine the surface anatomy of sciatic nerve by two points.

The first one is the middle point between posterior superior iliac spine

and the ischial tuberosity. The second one is the middle point between

ischial tuberosity and greater trochanter.

Posterior cutaneous nerve of the thigh

Originates from sacral plexus (S1, S2, S3), then enter the gluteal region

through the greater sciatic foramen below the piriformis.

It supplies the posterior skin of the thigh, upper posterior part of the leg

and medial lower part of the gluteal region.

Popliteal fossa

The back of the knee. Have 4 borders: 2 upper & 2 lower borders.

1- Upper medial: Semitendinosus, Semimembranosus.

2- Upper lateral: Biceps femoris (long head).

3- Lower medial: medial head of gastrocnemius.

4- Lower lateral: lateral head of gastrocnemius (and plantaris, but

maybe absent).

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Floor: Upper part is femur, lower is

tibia, and capsule of knee joint

between them.

Roof: skin, superficial fascia and

deep fascia.

Contents:

1- vessels: Popliteal artery (most

deep, closest to the bone),

popliteal vein (posterior to

popliteal artery, continue as

femoral vein), small saphenous

vein (drain into popliteal vein).

2- nerves: tibial nerve (From the

upper angle to the lower angle),

common fibular nerve (from upper angle to lateral angle).

3- lymph nodes: from lateral side of the foot and leg.

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*Common fibular nerve turns around the neck of the fibula then divides

into 2 nerves: Superficial fibular nerve & deep fibular nerve.

*Common fibular nerve gives 2 branches: Lateral cutaneous nerve of

the calf (supplies the upper lateral side of the leg & the anterior lateral

side of the leg & the posterior lateral side of the leg) and Sural

communicating branch.

Tibial nerve gives a branch called Sural nerve (supplies the back of the

leg and lateral side of the foot.

Sural nerve goes along with small saphenous vein posterior to the lateral

malleolus.

Clinical case: If a patient was complaining of a mass on the popliteal

fossa what can the cause possibly be?

First thing you think about is the content of this fossa, and you see from

what the mass is arising. If it’s arising from the skin it could be sebaceous

cyst or lipoma, if it’s from the popliteal artery it could be aneurysm, and

it could be from the lymph node, or a tumor in the femur. (What the

doctor meant by this example is that we have many causes of swelling in

the popliteal fossa and it could be any on of them because of the variety

of the content).