3 Gluteal Region, Posterior Thigh and Popliteal Fossa
GLUTEAL REGION AND POSTERIOR THIGH
Learning Objectives
By the end of the course students will be able to:
- Describe the anatomy of the hip region. Include the osteology as well as the gluteal muscles, their nerve supply, and their actions in locomotion.
- Identify the nerves and vessels of the hip and thigh region.
- Describe the muscular anatomy of the posterior thigh. Include its muscles, their nerve supply, and their actions in locomotion.
- Predict the functional loss and cutaneous areas affected by a given nerve injury to the hip and posterior thigh region; or conversely, given a functional and/or cutaneous loss, be able to predict which nerve or nerves are involved and the probable level of the injury.
- Define the popliteal fossa and give the spatial relationships of its contents.
- Explain the general plan of the collateral circulation at the hip and knee and the clinical consequences of the rupture of these vessels.
- Identify the muscles of the posterior compartment of the leg and give their functional significance in locomotion.
- Identify important bursae in the gluteal region.
Reference: Moore, Clinically Oriented Anatomy, chapter 5
Particularly relevant Blue Boxes in Moore:
●Ischial and Trochanteric Bursitis, p. 581
●Hamstring Injuries, p. 581
●Injury to Superior Gluteal Nerve (Trendelenburg Sign), p. 581-2
●Injury to Sciatic Nerve, p.582
●Intragluteal Injections, p. 582-3
●Popliteal Pulse, p.604
● Popliteal Aneurysm and Hemorrhage, p.604-5
● Injury to Tibial Nerve, p. 605
To access the Netter Presenter Database click here
Grant’s Dissector, 15th Edition, pp 176 – 184
To access the Gray’s Photographic Dissector section on the Gluteal Region click here
To access the Primal Pictures software click here
Check out the Primal Pictures model on the Gluteal Region and Posterior Thigh
GLUTEAL REGION (Moore p. 562-569)
Osteology and Ligaments (Netter 333, 334)
On the posterior aspect of the pelvis, the greater and lesser sciatic foramen act as important conduits for nerves and vessels. The greater sciatic notch of the pelvis, forms the major portion of the greater sciatic foramen; the lesser notch forms the lesser sciatic foramen. The two foramina are separated from each other by the sacrospinous ligament, which passes transversely from the sacrum to the ischial spine of the pelvis. The medial border of both foramen is formed by the sacrotuberous ligament, which lies perpendicular and superficial to the sacrospinous ligament (Moore p.563).
Muscles in Gluteal Region (see table 5.6 in Moore, p.564)
The most superficial muscle in the gluteal region is the gluteus maximus muscle (Netter 481, 482). It is innervated by the inferior gluteal nerve (Netter 491) and acts to extend the thigh at the hip joint and helps to laterally rotate it.
Underneath the gluteus maximus, the gluteus medius and minimus, piriformis, quadratus femoris, obturator internus and gemelli muscles come into view (Netter 482, 490). The key to orientating yourself in the gluteal region is the piriformis muscle. The PIRIFORMIS MUSCLE emerges through the greater sciatic foramen and passes infero-laterally to attach to the greater trochanter of the femur. The piriformis acts as a lateral rotator of the thigh and helps to hold the head of the femur into the acetabulum.
Several structures emerge through the greater sciatic foramen along the inferior border of the piriformis muscle: the inferior gluteal vessels and nerve, sciatic nerve, posterior femoral cutaneous nerve, pudendal nerve, and internal pudendal vessels (Netter 489). The pudendal nerve and internal pudendal vessels disappear immediately from view by passing through the lesser sciatic foramen into the ischio-rectal fossa. As these structures emerge from the greater sciatic foramen along the inferior border of the piriformis they pass superficial to the sacrospinus ligament, but deep to the sacrotuberous liagment, making them difficult to visualize. These structures then pass into the pudendal canal (Alcock’s canal), which is made from a split in the fascia on the medial surface of the OBTURATOR INTERNUS muscle (described later).(see Netter 380 and Moore fig 5.38)
The gluteus medius and minimus are both strong abductors of the thigh. They also act to stabilize the pelvis during walking (lifting one foot off the ground). Four other muscles are present in the gluteal region and all are located inferior to piriformis. The obturator internus enters the gluteal region through the lesser sciatic foramen. The tendon of this muscle may be partially obscured by fibers of the inferior and superior gemelli muscles, which can insert on this tendon.
Nerves of the Gluteal Region (Netter 489, 490, Moore 572-577)
Immediately deep to the gluteus maximus, is the gluteus medius muscle, and deep to gluteus medius is gluteus minimus. Both the gluteus medius and minimus muscles are superior and lateral in relation to the piriformis. Nerves and blood vessels that are superior to the piriformis muscle are labeled superior gluteal These nerves and vessels continue laterally in the fascial plane between the gluteus medius and gluteus minimus muscles to supply the tensor fascia lata muscle.
The sciatic nerve passes through the greater sciatic foramen inferior to the piriformis muscle. The posterior femoral cutaneous nerve is closely associated with it. The sciatic nerve is actually composed of two major nerves, which split into a medial and lateral component. The medial component is known as the tibial nerve and the lateral component the common peroneal nerve. The sciatic nerve innervates the hamstring muscles of the posterior thigh and all the muscles below the knee, including the sole of the foot.
The quadratus femoris muscle passes from the ischial tuberosity to the femur. It is located just inferior to the gemelli muscles.
Deep to the quadratus femoris it is possible to visualize the obturator externus muscle with medial rotation of the femur. The obterator externus runs between the ischium and the femur.
The nerve supply to this area is the following:
- Gluteus medius, minimus – superior gluteal nerve
- Gluteus maximus – inferior gluteal nerve
- Piriformis – nerve to piriformis
- Quadratus Femoris – nerve to quadratus femoris
- Superior Gemellus – branch of nerve to piriformis
- Inferior Gemellus – branch of nerve to quadratus femoris
- Obturator Externus – obturator nerve
- Obturator Internus – nerve to obturator internus
The posterior femoral cutaneous nerve (Netter 489) is the major cutaneous sensory supply to the posterior thigh. It passes through the greater sciatic foramen alongside the sciatic nerve in order to reach the posterior thigh.
The sciatic nerve (Netter 486, 489) arises from the sacral plexus from the ventral primary rami of L4 – S3, and is the largest nerve in the body. It divides at the superior border of the popliteal fossa into the tibial nerve, which runs through the fossa to disapper deep to the gastrocnemius, and the common peroneal nerve, which runs along the mediall border of the biceps femoris and superficial to the lateral head of the gastrocnemius.
The sciatic nerve enters the buttocks through the greater sciatic foramen below the piriformis, then descends over the obturator internus, genelli and quadratus frmoros muscles between the ischial tuberosity and the greater trochanter. Although the sciatic nerve passes through the gluteal region, it supplies no muscles in that region. It innervates the hamstring muscles by its tibial division, except fo rthe short head of biceps femoris, which is innervated by the common peroneal nerve. Damage to the sciatic nerve causes impaired extension at the hip and impaired flexion at the knee, loss of dorsiflexion and plantar flexion at the ankle, inversion and eversion of the foot and peculiar gait because of increased flexion at the hip to lift the dropped foot off the ground.
Arteries of the Gluteal Region
The superior gluteal artery (Netter 489) arises from the internal iliac artery (Netter 376) , and enters the gluteal region through the greater sciatic foramen above (hence the name – superior) the piriformis muscle. It runs deep to the gluteus maximus muscle and divides into a superficial branch that supplies that muscle and a deep branch which supplies the gluteus medius and minimus an dthe tensor fascia lata.
The inferior gluteal artery also arises from the internal iliac artery and enters the gluteal region through the greater sciatic firamen below the piriformis muscle. It supplies the gluteus maximus muscle, the lateral rotators of the hip, the hamstrings and the hip joint. It enters the cruciate anastamosis and also anastamoses with the superior gluteal, internal pudendal and obturator arteries.
Iliotibial Tract and Gluteal Aponeurosis (Netter 481, Moore 566-569)
Fascia Lata, the connective tissue that invests the thigh, is a fairly thin layer of tissue. It is thickened in two locations to form the iliotibial tract and the gluteal aponeurosis. The iliotibial tract is a laterally placed thickening stretching from the crest of the ilium to the lateral tibial condyle. Part of the gluteus maximus inserts into this iliotibial tract, while the tensor fascia lata muscle is completely encased in the tract. Both muscles in the tract act to help stabilize the knee joint when it is fully extended.
The gluteal aponeurosis is a thickening of the fascia lata that extends distally from the iliac crest. It is superficial to the gluteus medius and superior to gluteus maximus. This aponeurosis provides an origin to a significant portion of the gluteus medius muscle whose extensive origin also includes much of the lateral surface of the ilium.
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Gluteal Region – Clinical Considerations In thinking of the gluteal region, the most obvious place to start is with the gluteus maximus muscle. This muscle is of value in regard to the positioning of the sciatic nerve. The significance of the muscle is two-fold: 1. Using the midpoint of the inferior border of the muscle, the gluteal fold, one could approximate on the posterior thigh, the pathway of the sciatic nerve for injection of an anesthetic agent for relief of pain (Blue Box p. 582). 2. When giving injections one must take into account the pathway of the nerves in the gluteal region so there is no damage the nerve. The obvious tendency would be to use the mid-point of the buttocks. This, however, places the needle directly in line with the sciatic nerve and could cause damage. In order to prevent this from happening, mentally divide the buttocks into four sections. All injections should be placed in the superior-lateral (upper-outer) quadrant, well-away from the nerve. The fluid will then be injected into the substance of the gluteus maximus or medius muscles (Blue Box p. 582). 3. In the normal, anatomic position, the line between the two anterior superior iliac spines is parallel to the ground. When walking, one foot must be lifted from the ground; this is accomplished by stabilizing the pelvis. The pelvis is stabilized by contracting the abductor muscles-the gluteus medius and minimus-on the leg that is still grounded. If the gluteus medius and minimus were ever paralyzed, that individual would be incapable of stabilizing their pelvis and would walk with a characteristically lurching gait. When a person has any of the following disabilities: 1. Paralysis of gluteus medius and minimus, 2. un-united fracture of the neck of the femur, the pelvis will sag on the unsupported side. Since the pelvis is no longer stabilized, the pelvis will sag due to the body weight bearing down on the unsupported (foot raised) side. This is known as a positive Trendelenburg sign (Blue Box p. 581-582). Click here to view a Youtube video of a person walking with a Trendelenburg gait. 4. Piriformis Syndrome is a condition in which the piriformis muscle irritates and places pressure on the sciatic nerve, causing pain in the buttocks and referring pain along the course of the sciatic nerve. This referred pain, called sciatica, in the lower back and hip radiates down the back of the thigh and into the lower back. It can be treated with progressive piriformis stretching. |
Posterior Thigh (Netter 482, Moore p. 569-572)
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The posterior thigh contains the “hamstring” muscles* (see table 5.7 in Moore, p. 570), which act in extension of the thigh and flexion of the leg. These include the semimembranosus, semitendinosus, biceps femoris, and ischiocondylar portion of the adductor magnus muscles. The biceps femoris muscle has two portions, a long and short head. With the exception of the short head of biceps femoris, all of these muscles arise from the ischial tuberosity and are innervated by the tibial division of the sciatic nerve. The short head of biceps femoris arises from the posterior aspect of the femur and is innervated by the common peroneal portion of the SCIATIC NERVE * called this because butchers often hang hams up on hooks by these muscles Flexion of the leg at the knee is accomplished by the hamstrings and the sartorius (from the anterior thigh). Because the hamstrings cross the hip and knee joints (extending the thigh and flexing the knee) their efficiency at the knee is greatest when the hip is flexed. |
Posterior Thigh Blood Supply (Netter 499, Moore p. 575-6)
The blood supply for the hamstrings is provided by the three perforating branches of the deep femoral artery. These branches pass around the medial aspect of the thigh to reach the posterior compartment where they serve as muscular branches. The most superior portion of the posterior thigh receives arterial branches from the medial and lateral femoral circumflex arteries.
Popliteal Fossa (Netter 503, 504, Moore, 584-587)
The POPLITEAL FOSSA is a diamond-shaped space at the back of the knee filled with fat, nerves, vessels, and lymph nodes. This space has a roof, boundaries, and floor.
The roof is formed by the overlying skin, superficial fascia, and fascia lata. Muscles and tendons of the thigh and leg, which cross the knee joint posteriorly, form the boundaries of this space. The superior boundary is formed by the hamstring muscles; the biceps femoris form the lateral boundary and the semi muscles the medial. The two heads of the gastrocnemius muscle form the inferior boundary medially and laterally. Each head of the gastrocnemius attaches to one of the femoral condyles, deep to the hamstring muscles. The floor has a superior and inferior component. The superior half of the floor is made by the posterior surface of the femur. The inferior half of the floor is formed by fibers and ligaments of the knee joint capsule and by the popliteus muscle. The popliteus muscle passes from the lateral condyle of the femur to the posterior medial aspect of the tibia.
From the Netter picture references, notice the contents of the popliteal fossa:
●The Popliteal artery (continuation of the “superficial” femoral artery). Notice the five major branches of the popliteal artery (Netter 500):
- Superior lateral genicular artery
- Superior middle genicular artery
- Middle genicular artery (enters into the knee joint)
- Inferior lateral genicuar artery
- Inferior medial genicular artery
●Popliteal vein, with the Small saphenous vein emptying into it.
●Tibial nerve (a terminal branch of the sciatic nerve)
●Medial sural cutaneous nerve branching of the tibial nerve to run alongside the small saphenous vein
●Common fibular (peroneal) nerve
●Notice also the lateral sural cutaneous nerve branching off the common fibular (peroneal) nerve
Clinical Considerations:
A popliteal aneurysm ( a dilation of the popliteal artery) usually results in edema and pain in the popliteal fossa. If it is necessary to ligate the femoral artery for surgical repair, blood can bypass the occlusiion through the genicular anastamoses and reach the popliteal artery distal to the ligation.
Baker’s cysts are collections of fluid in the back of the knee which can occasionally be confused with a popliteal artery aneurysm. A Baker’s cyst is usually the result of a problem in the knee joint which is causing inflammation of the joint space. Examples are traumatic injuries to the joint or inflammatory conditions such as arthritis. Baker’s cysts generally occur in adults over the age of 50, and its treatment consists of correcting the underlying problem in the knee joint which has led to the development of the cyst. Occasionally, the cysts become very large and can press on adjacent structures such as veins resulting in swelling of the entire leg below the knee. In situations such as this, the Baker’s cyst is sometimes drained with a needle in order to relieve the pressure created by the cyst.
Gluteal Region, Posterior Thigh and Popliteal Fossa Quiz – click here