Muscles of the gluteal region and posterior thigh

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Introduction0:00–0:19

When looking at the lower limb from the posterior view, there are two regions that stand out immediately: the gluteal region and the posterior thigh.
Let’s start with what’s arguably the most popular one of the two and which has been featured in countless pop songs - the gluteal region.

Gluteal region0:19–3:00

The gluteal region is situated posterior to the pelvis and inferior to the iliac crest. Laterally it overlies the greater trochanter, and anteriorly, it extends up to the anterior superior iliac spine.
It also extends from the iliac crest superiorly to the gluteal fold inferiorly. The gluteal fold is the crease formed by the inferior aspect of the buttocks and the posterior upper thigh.
Medially, the region extends to the mid-dorsal line and is called the intergluteal cleft, which is the groove that separates the buttocks from each other.
Actually, before we move on, let’s review some important landmarks to help you understand this region’s anatomy better. First, the posterior sacroiliac ligament is the posterior continuation of the fibrous capsule of the synovial part of the sacroiliac joint, and continues inferiorly with the sacrotuberous ligament.
The sacrotuberous ligament goes from the posterior surface of the ilium and the lateral surfaces of the sacrum to the ischial tuberosity.
A similar ligament, called the sacrospinous ligament, passes from the lateral surface of the sacrum and the coccyx to the ischial spine.
These two ligaments convert the greater and lesser sciatic notches into greater and lesser sciatic foramina. Simply put, the greater and lesser sciatic foramina are passageways, or “doors” for structures leaving the pelvis and entering the gluteal region and vice versa.
The structures passing through the greater sciatic foramen include the piriformis muscle and the structures that leave the pelvis above it, mostly represented by the superior gluteal vessels and nerve and the structures that leave the pelvis below it - the sciatic nerve, pudendal nerve and internal pudendal vessels, inferior gluteal nerve and vessels, posterior femoral cutaneous nerve and the nerves to obturator internus and quadratus femoris.
The lesser sciatic foramen, on the other hand, provides passage for structures entering or leaving the perineum, including the tendon and nerve of obturator internus as well as the pudendal nerve and vessels.
Ok, so the gluteal region is mostly considered a large transitional zone between the trunk and the lower limb. The muscles of the gluteal region are organized into two layers, the superficial containing the three large overlapping gluteus muscles, and the deep layer consisting of smaller muscles which all have distal attachments on or near the greater trochanter of the femur, providing lateral rotation and stabilization of the femur.

Superficial - Gluteus maximus3:00–5:44

Let's start superficially and talk about one of the most well known muscles in the body. The Gluteus maximus is the most superficial of the bunch and it’s also the largest and the heaviest muscle of the body.
Quite the overachiever! More importantly, it originates posterior to the posterior gluteal line of the ilium, on the dorsal surface of the sacrum and coccyx, and on the sacrotuberous ligament.
It then slopes inferolateral at a 45° angle from the pelvis to the buttocks, where fibers from its superior part alongside superficial fibers from its inferior parts insert into the iliotibial tract, a longitudinal fibrous reinforcement of the fascia lata which crosses the knee and attaches to the anterolateral tubercle of the tibia.
Additionally, some of the deep fibers of the inferior part of the muscle attach to the gluteal tuberosity of the femur. The gluteus maximus is supplied by the inferior gluteal nerve from roots L5, S1 and S2, and by both the inferior and superior gluteal arteries.
And when it comes to actions, it steadies, extends, and laterally rotates the thigh, it helps with getting up from a sitting position, and, when the distal attachment of the gluteus maximus is fixed, the muscle extends the trunk on the lower limb.
It also helps us straighten from bending positions, like when walking up stairs or hills. Finally, since the gluteus maximus inserts onto the iliotibial tract, it also assists in stabilizing the extended knee.
Oh, and while at it, we should mention that the gluteus maximus is separated from adjacent structures by the gluteal bursas.
Bursas are membranous sacs lined by a synovial membrane containing a capillary layer of slippery fluid resembling egg white that lubricates overlying structures to counteract friction and permit free movement .
The fluid is a lubricant, which is why bursas are typically located in areas subject to friction, like where the iliotibial tract crosses the greater trochanter, to reduce friction and permit free movement.
There are three bursas associated with the gluteus maximus. First is the trochanteric bursa which is the largest of the three, and it separates the superior fibers of the gluteus maximus from the greater trochanter.
Second, the ischial bursa separates the inferior part of the gluteus maximus from the ischial tuberosity; however, this one is often absent.
And third, the gluteofemoral bursa separates the iliotibial tract from the superior part of the proximal attachment of the vastus lateralis.
Now, deep to the gluteus maximus are the gluteus medius and minmus. These two muscles are both fan-shaped and they both originate on the external surface of the ilium.

Superficial - Gluteus medius & Gluteus minimus5:44–6:51

Specifically, gluteus minimus originates between the anterior and inferior gluteal lines of the surface and it inserts on the anterior surface of the greater trochanter of the femur.
The gluteus medius, on the other hand, is between the posterior and anterior gluteal lines and inserts on the lateral surface of the greater trochanter.
The two glutei also share the same nerve supply, namely the superior gluteal nerve, the same blood supply, through the superior gluteal artery; and have the same actions, which is abducting, stabilizing, and rotating the thigh medially.
These muscles are also important for walking and standing, as they keep the pelvis level during walking when the ipsilateral leg is planted and prevents sagging of the unsupported contralateral side during swing phase or standing.
And the final muscle of the superficial layer is tensor fascia lata, which is a spindle-shaped muscle, approximately 15 centimeters long, that is enclosed between the two layers of fascia lata.

Superficial - Tensor fascia lata6:51–7:58

It originates on the anterior superior iliac spine and on the anterior part of the iliac crest. From this point, it descends on the superficial and anterior part of the gluteus maximus, with which it shares a common distal attachment, the iliotibial tract, via which it inserts on the lateral condyle of the tibia.
However, unlike the gluteus maximus, the tensor fasciae latae is served by the superior gluteal nerve and artery. When it comes to movement, it has the same actions as gluteus minimus and medius, which is abducting, stabilizing, and rotating the thigh medially, as well as keeping the pelvis stable when only one leg is weight bearing.
It also serves as a hip flexor due to its anterior location, and, as its name indicates, it tenses the fascia lata and iliotibial tract.
And now let’s have a small break and test you out to see if you can remember the origins and insertions of the superficial muscles of this region.

Quiz7:58–8:12

Let’s move on to the deep layer, which consists of five muscles covered by the inferior half of the gluteus maximus: the piriformis, obturator internus, superior and inferior gemelli, and quadratus femoris.

Deep layer8:12–8:48

Actually, there’s also a sixth muscle called obturator externus, which is physically part of the adductor compartment of the thigh but it is functionally related to this region as it is a lateral rotator of the thigh, so think of it as an honorary member of the gluteal region.
Ok, first, the piriformis is pear-shaped, hence its name, and it’s located partly on the posterior wall of the lesser pelvis, and partly posterior to the hip joint.

Deep - Piriformis8:48–9:35

The piriformis originates on the anterior surface of the sacrum and the sacrotuberous ligament, then it leaves the pelvis through the greater sciatic foramen, and it inserts on the superior border of the greater trochanter.
The muscle is directly supplied by branches from the anterior rami of S1 and S2 spinal nerves. The piriformis, along with the obturator internus and the superior and inferior gemelli are responsible for laterally rotating the extended thigh, abducting the flexed thigh, and steadying the femoral head in the acetabulum.
The next three muscles, the obturator internus and the superior and inferior gemelli also known as the twins, form a three-headed muscle called the triceps coxae or the triceps of the hip.

Deep - Triceps coxae (obturator internus, superior and inferior gemelli)9:35–10:30

The triceps coxae occupies the gap between the piriformis and the quadratus femoris. Regarding proximal attachments, the obturator internus originates on the pelvic surface of the obturator membrane and surrounding bones; the superior gemellus on the ischial spine; and the inferior gemellus on the ischial tuberosity.
All three muscles then have the same insertion point on the medial surface of the greater trochanter of the femur. The obturator internus and superior gemellus are both supplied by the nerve to the obturator internus, while the inferior gemellus, and the muscle underneath it, quadratus femoris, are supplied by the nerve to quadratus femoris.

Deep - Quadratus femoris10:30–11:06

Speaking of which, the quadratus femoris is a short, flat quadrangular muscle, situated just underneath the obturator internus and the twin gemelli.
True to its name, the quadratus femoris is a rectangular muscle that originates on the lateral border of the ischial tuberosity.
The muscle has a horizontal trajectory as well, and it goes on to insert on the quadrate tubercle, on the intertrochanteric crest of the femur.
As mentioned, it is supplied by the nerve to quadratus femoris and it’s responsible for rotating the thigh laterally and steadying the femoral head in the acetabulum.
Time for a break and to put those brain muscles to rest. Meanwhile, to reward yourself, try and recognize the origins and insertions of the deep muscles of the gluteal region.

Quiz11:06–11:23

Now let’s switch gears and look at the muscles of the posterior thigh, collectively known as the hamstrings. This group consists of the semitendinosus, semimembranosus, and biceps femoris.

Posterior thigh (Hamstrings)11:23–12:05

Generally speaking, the hamstrings originate on the ischial tuberosity, they project downward to insert on the bones of the leg, and cross both the hip and knee joint to extend the hip and flex the knee.
However, it is important to note that the biceps femoris muscle has two heads; the long head and short head. Only the long head is considered a hamstring muscle, as the short head does not have the same features as the other three muscles The semitendinosus, called that because half of the muscle is represented by a muscular belly and half by its cord-like tendon, originates on the ischial tuberosity and inserts on the medial surface of the superior part of the tibia.

Posterior thigh - Semitendinosus & Semimembranosus12:05–13:29

The semimembranosus, named that because of its membrane-like origin, also originates on the ischial tuberosity and has a direct insertion on the posterior aspect of the medial tibial condyle.
It also blends with the popliteal fascia and has a reflected attachment which forms the oblique popliteal ligament. The insertion onto the medial tibia of the semitendinosus, along with the sartorius and gracilis muscle, is collectively known as the pes anserinus, which means “goose foot”, because it resembles...you know a goose’s foot.
Alright, now, Innervation to the semitendinosus and semimembranosus is provided by the tibial division of the sciatic nerve from nerve roots L5, S1 and S2, whereas blood is supplied by the profunda femoris and gluteal arteries.
These two muscles extend the thigh, flex the leg and rotate it medially when the knee is flexed and, when both the thigh and leg are flexed, they can extend the trunk.
The biceps femoris has both a long head and a short head. The long head originates on the ischial tuberosity, whereas the short head originates on the linea aspera and lateral supracondylar line of the femur.

Posterior thigh - Biceps femoris13:29–14:21

These two heads merge in the inferior part of the thigh to form a tendon that inserts on the lateral surface of the head of the fibula, where it is split by the fibular collateral ligament of the knee.
The long head of the biceps is supplied by the tibial division of the sciatic nerve while its short head is supplied by the common fibular division of the sciatic nerve with both being from L5, S1, and S2, and the profunda femoris artery.
The biceps flexes the leg and rotates it laterally when the knee is flexed, and, additionally, it extends the thigh. That wasn’t too thigh-ring, now was it?

Quiz14:21–14:37

Before we wrap up, let’s try to recall the origins and insertions of the hamstrings! ##Summary Alright, as a quick recap…The sacrotuberous ligament and the sacrospinous ligament, convert the greater and lesser sciatic notches into greater and lesser sciatic foramina.

Review14:37–15:36

The greater sciatic foramen allows for the passage of structures entering and exiting the pelvis, where the lesser sciatic foramen allows for structures entering and exiting the perineum.
The superficial muscles consist of the gluteus maximus, gluteus medius, gluteus minimus, and the tensor fascia lata. The deep muscular layer of the gluteal region consists of the piriformis, triceps coxae, which is formed by the obturator internus and the two gemelli and the quadratus femoris.
The posterior thigh muscles are the three hamstrings, namely the semitendinosus, semimembranosus, and long head of biceps femoris.