9. Anatomy of the hip, gluteal region and posterior thigh Flashcards
What type of joint is the hip?
Ball and socket:
• Ball (femoral head)
• Socket (acetabulum of hip bone)
Describe the strength and movement of the hip joint
• Large range of movement
• Strong joint
- Takes a lot to disrupt
- Very stable joint
What is the pelvic girdle?
the bony structure that attaches the axial skeleton to the lower limbs
What forms the pelvic girdle?
The left and right hip bones and the sacrum
What type of bone are the hip bones?
Irregular
What are the three main articulations found in the hip bones?
- sacroiliac joint: articulation with the sacrum
- pubic symphysis: articulation between left and right hip bones
- hip joint: articulation with the head of the femur
What three parts is the hip bone comprised of?
The ilium, the pubis and the ischium
What is the difference between the hip bone in children and in adults?
In children - ilium, pubis and ischium are separated by triradiate cartilage
Fusion begins between the ages of 15-17 years and is complete by 20-25
Adult: ilium, pubis and ischium form a cup-shaped socket known as the acetabulum which the head of the femur articulates with to form the hip joint
What is the ilium?
- widest/ largest part, forms superior part of the acetabulum
- immediately above the acetabulum, the ilium expands to form the wing (or ala).
What are the two surfaces of the wing of the ilium?
- Internal surface – has a concave shape, which produces the iliac fossa (site of origin of the iliacus muscle).
- External surface (gluteal surface) – has a convex shape and provides attachments to the gluteal muscles.
What is the iliac crest?
The superior margin of the wing is thickened, forming the iliac crest. It extends from the anterior superior iliac spine (ASIS) to the posterior superior iliac spine (PSIS)
What is the greater sciatic notch?
On the posterior aspect of the ilium there is an indentation known as the greater sciatic notch
What is the pubis?
The pubis is the most anterior portion of the hip bone. It consists of a body, a superior ramus and an inferior ramus (ramus = branch)
What is the pubic symphysis and pubic crest?
Located medially, the pubic body articulates with the opposite pubic body at the pubic symphysis. Its superior aspect is marked by a rounded thickening (the pubic crest), which extends laterally as far as the pubic tubercle.
What is the Superior pubic ramus?
This extends laterally from the pubic body to the
acetabulum
What is the Inferior pubic ramus?
This extends laterally from the pubic body join with the
inferior ischial ramus. Together they form the ischiopubic ramus
Describe the obturator foramen
Together, the superior and inferior pubic rami enclose part of the obturator foramen, through which the obturator nerve, artery and vein pass through to reach the lower limb.
What is the ischium? Where is it and what is it composed of?
- posteroinferior part of hip bone
- composed of a body, inferior ramus and superior ramus
- posteroinferior aspect forms the ischial tuberosity
- near the junction of the superior ramus and body is a posteromedial projection of bone; the ischial spine
What ligaments attach to the ischium?
- Sacrospinous ligament: This runs from the ischial spine to the sacrum, thereby creating the greater sciatic foramen through which many nerves and vessels pass to enter the lower limb.
- Sacrotuberous ligament: This runs from the sacrum to the ischial tuberosity, forming the lesser sciatic foramen
What is the function of the ligaments that attach to the ischium?
These ligaments limit rotation of the inferior part of the sacrum during transmission of weight of the body down the vertebral column in the erect position.
What is the function of the hip joint?
enable mobility of the lower limbs without weakening the ability of the lower limbs to support the weight of the body.
Describe the acetabulum
- The acetabulum forms a cup-like socket on the inferolateral aspect of the pelvis.
- A fibrocartilaginous collar, the acetabular labrum, encircles the acetabulum,
- both the acetabulum and head of femur are covered in hyaline cartilage
- the articular surface of the acetabulum is shaped like a horseshoe and is incomplete in the acetabular notch region
- the acetabular notch contains fibroelastic fat covered with synovial membrane
- Where hip bones converge
What does the acetabular labrum do?
- encircles the acetabulum, deepening it and providing a secure fit for the hemispherical femoral head
- increases articular contact area by 10% so that more than 50% of the femoral head is in contact with the socket at any time
- increases stability
What is the fovea capitis?
a small pit in the centre of the femoral head where the ligament of the head of the femur attaches (ligamentum teres)
Describe the structure of the femur
- the neck connects the head to the shaft: it passes inferiorly, posteriorly and laterally, making an angle of 125 degrees with the long axis of the shaft
- shaft is smooth and rounded. Posteriorly there’s a ridge called the linea aspera to which the inter muscular septa and many muscles of the thigh attach.
- the gluteal tuberosity lies between the upper end of the linea aspera and the intertrochanteric crest - site of insertion of the gluteus maximum muscle of the buttock.
- inferiorly, the linea aspera diverges to form the lateral and medial supracondylar lines.
- the medial margin continues inferiorly as the medial supracondylar line and terminates at the adductor tubercle on the medial condyle of the femur
- the lateral margin of the linea aspera continues inferiorly as the lateral supracondylar line which terminates at the lateral condyle
- the condyles are separated by the intercondylar notch posteriorly
- on the anterior surface is the articular surface for the patella which lies between the two condyles - trochlear/ patellofemoral groove
- both medial and lateral femoral condyles form the knee joint
Describe the greater and lesser trochanters, including what they are connected by anteriorly and posteriorly
The greater and lesser trochanters are large bony prominences at the proximal end of the femoral shaft. On the anterior aspect, they are connected by the intertrochanteric line and on the posterior aspect by the intertrochanteric crest
How is the capsule of the hip joint attached? (Proximally and distally)
- proximally: attaches to the edge of the acetabulum, 5-6 mm outside the acetabular labrum
- distally: attaches to the intertrochanteric line of the femur anteriorly and the femoral neck posteriorly
What are longitudinal retinacula?
Anteriorly on the femur, the capsular fibres ascend along the neck as longitdunal retinacula, containing blood vessels for the femoral head and neck
What are the three extracapsular ligaments of the hip joint?
iliofemoral, pubofemoral and ischiofemoral ligaments
What is the only intracapsular ligament of the hip joint?
ligamentum teres
Describe the position of the iliofemoral ligament
- strongest in body
- inverted Y shape
- lies superior and anterior to hip joint and blends with capsule
- base of the Y is attached to the anterior inferior iliac spine of the ilium
- the limbs of the Y are both attached to the intertrochanteric line of the femur
What does the iliofemoral ligament do?
- screws the head of the femur into the acetabulum
- prevents the trunk from falling backwards without the need for muscular acitivity i.e. prevents hyper extension of the hip
- relaxes when seated to permit pelvis to tilt backward into its sitting position
Describe the position of the pubofemoral ligament?
- lies inferior and anterior to the hip joint
- triangular
- its base is attached to the superior pubic ramus of the pelvis and its apex to the inferior part of the intertrochanteric line anteriorly
What is the role of the pubofemoral ligament?
Prevent excessive abduction and extension of the hip joint
Describe the position of the ischiofemoral ligament?
- spiral shaped
- attached to the body of the ischium posteriorly
- its inferior fibres spiral superolaterally from the ischium body to attach to the superolateral end of the intertrochanteric line of the femur, anteromedial to the base of the greater trochanter (so it wraps all the way round the back of the femoral head and neck and inserts anteriorly, deep to the lateral fibres of the iliofemoral ligament)
- weakest of ligaments
What is the job of the ischiofemoral ligament?
Prevents excessive internal (medial) rotation
What does the transverse acetabular ligament do?
- It is formed by the acetabular labrum as it bridges the acetabular notch
- This converts the notch into a tunnel for blood vessels/ nerves to enter the hip joint
What are the hip joint ligaments?
Capsule is strengthened by 3 strong ligaments
- Iliofemoral
- Pubofemoral
- Ischiofemoral
Accessory ligaments:
• Ligament of head of femur - (ligamentum teres)
• Transverse acetabular ligament
What does the synovial membrane line?
- Lines the capsule and is attached to the margins of the articular surfaces
- It ensheathes the ligamentum teres and covers the pad of fat contained in the acetabular fossa
What factors act to increase the stability of the hip joint?
The cup-shaped acetabulum
The acetabular labrum, which deepens the acetabulum
The capsule
The ligamentum teres (ligament of the head of the femur or round ligament)
The extracapsular ligaments: iliofemoral, pubofemoral and ischiofemoral
The muscles surrounding the hip joint
What is the relationship between the impact of muscles and ligaments in the hip joint?
- Work in a reciprocal fashion
- Where the ligaments are strongest anteriorly, the medial flexors are fewer/ weaker
- Posteriorly where the ligaments are weakest, the lateral rotators are more numerous/ stronger and pull the femur head into the acetabulum
Which muscles are involved in flexion of the hip?
Main flexor: Iliopsoas (iliacus + psoas major)
• Two separate muscles that merge
• Insert into lesser trochanter
• Nerve supply (lumbar plexus, L1-3)
Assisted by:
• Rectus femoris
• Sartorius
• Pectineus
Which muscles are involved in extension of the hip?
Gluteus maximus
Hamstrings: semimembranosus, semitendinosus, biceps
femoris (long head)
Which muscles are involved in abduction of the hip?
Gluteus medius, gluteus minimus
Assisted by sartorius, tensor fascia lata
Which muscles are involved in adduction of the hip?
Adductor longus, adductor brevis, adductor magnus -
Assisted by pectineus, gracilis, obturator externus
Which muscles are involved in lateral rotation of the hip?
Obturator externus, piriformis, obturator internus,
superior and inferior gemelli, quadratus femoris
Assisted by gluteus maximus, sartorius
Which muscles are involved in medial rotation of the hip?
Anterior fibres of gluteus medius and minimus, tensor
fascia lata. Assisted by adductor brevis, adductor
longus, superior portion of adductor magnus, pectineus
What is flexion and extension limited by at the hip joint?
- Amount of flexion depends of whether the knee is also flexed as this relaxes the hamstring muscles
- Extension is limited by the joint capsule and the iliofemoral ligament which become taut to limit further extension
which nerves innervates the hip?
the hip joint is innervated primarily by the sciatic nerve posteriorly, femoral nerve anteriorly and obturator nerve inferiorly. The sciatic and femoral nerves also innervate skin around the knee (see figure 3.15), which explains why pain can be referred to the knee from the hip and vice versa. For completeness, the hip joint also receives innervation from the superior gluteal nerve superiorly (which supplies gluteus medius and minimus) and the nerve to quadratus femoris posteriorly.
How is blood supplied to the femoral head and neck?
- extracapsular arterial ring at the base of the neck - formed posteriorly by large branch of the medial femoral circumflex artery and anteriorly by smaller branches of the lateral femoral circumflex artery
- as the ascending cervical arteries (retinacular arteries) cross the surface of the neck, they send many small branches into the metaphysis of the neck
- the ligamentum teres contains the artery of the ligamentum teres, which arises most commonly from the obturator artery
Why does intracapsular fracture of the femoral neck carry a high risk of avascular necrosis adn why more so in the adult than in children?
- in the child the artery of the ligamentum teres is the major blood supply to the head
- In the adult, after epiphyseal fusion, only a small volume of the head near the fovea is adequately nourished by this artery
- the rest is nourished by the retinacular arteries
- intracapsular fracture disrupts these arteries, cutting off blood supply to the head
What does The lower limb receives its nerve supply via?
lumbosacral plexus
What is the lumbar component of the lumbosacral plexus formed from?
The lumbar component of the lumbosacral plexus is formed from the anterior rami of the L1-4 spinal nerves. These anterior rami divide into several cords which combine to form the major peripheral nerves of the lumbar plexus. These nerves descend on the posterior abdominal wall to the lower limb, where they innervate their target structures (e.g. skin, muscle).
what forms the lumbosacral trunk?
The L4 anterior ramus also gives off a branch which combines with the L5 anterior ramus to form the lumbosacral trunk. This contributes axons to the sacral plexus
What explains why extension of the knee (femoral nerve,
posterior divisions of lumbar plexus) extends the leg anteriorly, whereas extension of the elbow (radial nerve, posterior divisions of brachial plexus) extends the forearm posteriorly?
the posterior divisions of the lumbar plexus form the nerves that supply the anterior thigh. This should make
sense if you recall the internal (medial) rotation of the lower limb bud and that the great toe, which initially lies on the cephalic (head) side of the limb bud, rotates to lie medially
What is the lumbar plexus?
The lumbar plexus is a network of nerve fibres that supplies the skin and musculature of the lower limb. It is locates in the lumbar region, within the substance of the psoas major muscle and anterior to the transverse processes of the lumbar vertebrae.
The plexus is formed by the anterior rami(divisions) of the lumbar spinal nerves L1, L2, L3, L4. It also receives contributions from thoracic spinal nerve 12.
Describe the root and function of the ilioinguinal nerve
The ilioinguinal nerve has the root L1. Amongst other functions, it innervates the skin of the genitalia and the upper medial thigh
Describe the root and function of the genitofemoral nerve
The genitofemoral nerve has the roots L1 and L2. It divides into a genital branch and a femoral branch.
Describe the root and function of the lateral cutaneous nerve of the thigh
The lateral cutaneous nerve of the thigh (also known as the lateral femoral cutaneous nerve) is formed from the posterior divisions of the L2 and L3 roots. It has a purely sensory function and enters the thigh at the lateral aspect of the inguinal ligament, where it provides cutaneous sensation to the anterolateral thigh as far inferiorly as the knee
Describe the root and function of the obturator nerve
formed from the anterior divisions of the L2, L3 and L4
roots. It innervates the skin over the medial thigh and is the nerve of the medial compartment of the thigh
Describe the root and function of the femoral nerve
formed from the posterior divisions of the L2, L3 and L4 roots. It innervates the skin of the anterior thigh via its anterior femoral cutaneous branch and via its saphenous branch it also innervates the skin of the medial leg. The femoral nerve is the nerve of the anterior compartment of the thigh
What is a useful mnemonic for remembering the branches of the lumbar plexus and their root values?
“I get leftovers on Fridays” Ilioinguinal (L1) Genitofemoral (L1, L2) Lateral femoral cutaneous (L2, L3) Obturator (L2, L3, L4) Femoral (L2, L3, L4)
Describe what forms the sacral plexus and its destination
The sacral plexus is formed from the anterior rami of S1, S2, S3, S4 and S5. It also receives a contribution from L4 and 5 via the lumbosacral trunk. The nerves of the
sacral plexus have two main destinations: the lower limb; and the pelvic muscles, organs and perineum
Summarise the The branches of the sacral plexus that and their root values
Superior gluteal nerve (L4, L5, S1)
Inferior gluteal nerve (L5, S1, S2)
Sciatic nerve (L4, L5, S1, S2, S3) and its divisions
Posterior femoral cutaneous nerve (posterior cutaneous nerve of the thigh)
(S1-3)
Describe the root and function of the superior gluteal nerve
The superior gluteal nerve leaves the pelvis via the greater sciatic foramen and enters the gluteal region above the piriformis muscle, accompanied by the superior gluteal artery and vein. It has the root values
L4, L5 and S1. It has no sensory branches. It innervates the gluteus medius, gluteus minimus and tensor fascia lata muscles
Describe the root and function of the inferior gluteal nerve
The inferior gluteal nerve also leaves the pelvis via the greater sciatic foramen but enters the gluteal region below the piriformis muscle, accompanied by
the inferior gluteal artery and vein. It has the root values L5, S1 and S2. Like the superior gluteal nerve, it has no sensory branches. The only muscle it innervates is
gluteus maximus.
Describe the root and function of the posterior cutaneous nerve of the thigh
The posterior cutaneous nerve of the thigh (or posterior femoral cutaneous nerve) has the root values S1, S2 and S3 and is formed from branches of the posterior division of S1 and S2 and the anterior division of S2 and S3. It leaves the pelvis via the greater sciatic foramen below the piriformis muscle. The sacral plexus innervates the skin of the posterior thigh and leg
What is a useful mnemonic for remembering the branches of the lumbar plexus and their root values?
“Salmon is so perfectly pink” S Superior gluteal (L4, L5, S1) I Inferior gluteal (L5, S1, S2) S Sciatic (L4, L5, S1, S2, S3) P Posterior femoral (S1, S2, S3) P Pudendal (S2, S3, S4)
Which ligament converts the greater sciatic notch into the greater sciatic foramen?
sacrospinous ligament
Which ligament converts the lesser sciatic notch into the lesser sciatic foramen?
sacrotuberous ligament
What is the greater sciatic foramen bounded by?
The greater sciatic foramen is bounded inferiorly by the ischial spine and sacrospinous ligament, posteromedially by the upper fibres of the sacrotuberous ligament and anterolaterally the greater sciatic notch of the ilium.
Which structures exit the pelvis via the greater sciatic foramen inferior to the piriformis muscle?
Sciatic nerve
Inferior gluteal nerve, artery and vein
Posterior femoral cutaneous nerve
Nerve to quadratus femoris
Nerve to obturator internus
Pudendal nerve, inferior pudendal artery and vein;
Which structures exit the pelvis via the greater sciatic foramen superior to the piriformis muscle?
superior gluteal nerve and vessels
What is the lesser sciatic foramen bounded by?
The lesser sciatic foramen is bounded superiorly by the ischial spine and sacrospinous ligament, inferiorly by the ischial tuberosity, posteriorly by the sacrotuberous ligament and anterolaterally by the lesser sciatic notch
Which structures pass through the lesser sciatic foramen?
Tendon of obturator internus
Nerve to obturator internus
[Pudendal nerve (returning to the pelvis)
[Internal pudendal vessels (returning to the pelvis)
What is the largest nerve in the body?
sciatic nerve
What are the root values of the sciatic nerve?
root values L4, L5, S1, S2, and S3.
Where does the sciatic nerve lie in the gluteal region?
In the gluteal region, the sciatic nerve lies on the bone of the ischium, then on the superior gemellus, obturator internus, inferior gemellus and quadratus femoris muscles. It passes midway between the greater trochanter of the femur and the ischial tuberosity of the pelvis to enter the posterior compartment of the thigh. In the posterior thigh, the sciatic nerve lies on the posterior surface of the adductor magnus muscle and is crossed by the long head of the biceps femoris muscle
What are the two divisions of the sciatic nerve?
tibial nerve and common peroneal (common fibular) nerve at the superior end of the popliteal fossa (above the knee). The common peroneal and tibial nerves are both mixed sensory and motor nerves
Does the sciatic nerve have branches in the gluteal region?
no
What does the tibial nerve supply?
The tibial nerve supplies all of the hamstring muscles i.e. semitendinosus, semimembranosus, biceps femoris (long head) and the hamstring (ischial) part of adductor magnus in the posterior thigh
What does the peroneal nerve supply?
The common peroneal (common fibular) nerve supplies the short head of biceps femoris in the posterior thigh
When administering an intramuscular injection in the gluteal region, which nerve must not be injured?
sciatic nerve
When administering an intramuscular injection in the gluteal region, which site is used for children and which is used for adults?
The dorsogluteal site is used in children between the ages of three and seven years, whereas the ventrogluteal site is usually preferred in
children over seven years of age or in adults. The ventrogluteal site is further from the neurovascular structures but requires better patient compliance.
Describe how to locate the ventrogluteal site
you should place the palm of your hand over the
greater trochanter of the femur, point your thumb towards the inguinal region and your index finger toward the anterior superior iliac crest. Spread your
index and middle fingers to make a V and carefully inject between the proximal `interphalangeal joints of your fingers into the patient’s gluteus medius muscle
What is The deep fascia of the thigh called?
fascia lata
Describe the fascia lata
- It encloses the thigh muscles and is a site of attachment for the intermuscular septae which divide the thigh into three compartments: the anterior, medial and posterior compartments.
- Superiorly, it is continuous with the fascia of the abdominal wall and perineal region;
- inferiorly it is continuous with the deep fascia of the leg (crural fascia).
- The fascia lata is thinnest medially over the adductor muscles of the thigh.
what is the function of the saphenous opening in the fascia lata?
The saphenous opening in the fascia lata, just below the inguinal ligament, serves as an entry point for the saphenous vein (which drains into the femoral vein) and
for lymphatic vessels which drain into the superficial inguinal lymph nodes.
What is the iliotibial tract?
The iliotibial tract, also known as the iliotibial band, is a thick strip of connective tissue connecting several muscles in the lateral thigh. It plays an important role in the movement of the thigh by connecting hip muscles to the tibia of the lower leg.
Describe the tensor fascia lata
The tensor fascia lata (or tensor fasciae latae) muscle originates from the anterior superior iliac spine of the pelvis and inserts between the two layers of the iliotibial
band of the fascia lata at the junction between the upper and middle two thirds of the thigh. Tensor fascia lata is innervated by the superior gluteal nerve (L5, S1).
What is the function of the tensor fascia lata?
• By pulling on the iliotibial tract, tensor fascia lata helps to stabilise the hip in extension (assisting gluteus maximus during hip extension).
• By tightening the iliotibial tract in the standing position, tensor fascia lata and gluteus maximus help to stabilise the knee by steadying the condyles of the femur on the articular surfaces of the tibia.
• Tensor fascia lata can also assist gluteus medius and minimus to abduct the hip joint.
• As a minor action, it also ‘hoists’ the fascia lata upwards which has the effect of tightening the compartments of the thigh and compressing the deep veins (e.g.
femoral vein), therefore improving venous return from the lower limbs.
What are the two groups that muscles of the gluteal region can be divided into and which muscles do each contain?
• Superficial: This group of large muscles acts to abduct and extend the thigh. It includes the gluteus maximus, gluteus medius, gluteus minimus and tensor fascia lata muscles.
• Deep: This group of smaller muscles mainly acts to laterally rotate the femur. It includes the piriformis, gemellus superior, obturator internus, gemellus inferior and quadratus femoris muscles. Obturator externus is
also sometimes included in this group
Which arteries supply the muscles of the gluteal region?
The arterial supply to these muscles is mostly via the superior and inferior gluteal arteries, which are branches of the internal iliac artery. The venous drainage follows the arterial supply.
Describe the gluteus maximus
• largest of the gluteal muscles.
• most superficial, producing the rounded shape of the buttocks.
• originates from the gluteal (posterior) surface of the ilium, sacrum and coccyx.
• It crosses the buttock at a 45° angle.
• The superior and most superficial fibres insert into the iliotibial tract and the inferior and deeper fibres
insert into the gluteal tuberosity of the femur
What are the actions of the gluteus maximus?
• Gluteus maximus is the main extensor of the thigh and also assists with lateral (external) rotation at the hip.
• As a powerful extensor of the hip joint, it is most suited to powerful lower limb movements such as stepping onto a step, climbing or running but is not used much during normal walking.
• Gluteus maximus and the hamstrings work together to extend the trunk from a flexed position by tilting the pelvis backwards, for example when standing
up from a sitting position.
• The superior fibres of the gluteus maximus can also assist in extension of the knee through their attachment to the iliotibial tract.
Which nerve innervates the gluteus maximus?
Inferior gluteal nerve (L5, S1, S2).
Describe the gluteus medius
The gluteus medius muscle is fan-shaped and lies between the gluteus maximus and gluteus minimus muscles. It is similar in shape and function to the gluteus
minimus. Gluteus medius originates from the gluteal surface of the ilium and inserts into the lateral surface of the greater trochanter
What are the actions of the gluteus medius?
Gluteus medius abducts and medially (internally) rotates the lower limb. Whilst walking, it secures the pelvis in a horizontal alignment, preventing a downward tilt towards the unsupported limb
Which nerve innervates the gluteus medius?
Superior gluteal nerve (L4, L5, S1).
Describe the gluteus minimus
• deepest and smallest of the superficial gluteal
muscles.
• originates from the ilium and inserts onto the anterior aspect ofthe greater trochanter
What are the actions of the gluteus minimus?
Like gluteus medius, it abducts and medially (internally) rotates the lower limb. Whilst walking, it secures the pelvis in a horizontal alignment, preventing a downward tilt towards the unsupported limb
Which nerve innervates the gluteus minimus?
Superior gluteal nerve (L4, L5, S1).
What can cause Superior gluteal nerve injury?
- complication of hip surgery
- injections to the buttock,
- fractures of the greater trochanter (site of insertion of gluteus medius)
- dislocation of the hip joint.
What is the effect of Superior gluteal nerve injury?
- The superior gluteal nerve supplies the abductors of the hip: gluteus medius and minimus. A superior gluteal nerve lesion therefore leads to weakness in abducting the thigh at the hip.
- When a healthy person, standing erect, is asked to lift one foot off the ground, the gluteus medius and minimus of the supporting lower limb usually contract, preventing the tilting of the pelvis towards the unsupported side.
- When a person with a superior gluteal nerve palsy is asked to stand on their injured lower limb, the pelvis on the unsupported side descends. This clinical sign is referred to as a positive Trendelenburg sign.
What are deep gluteal muscle?
a set of smaller muscles, located deep to the gluteus
minimus
What is the function of deep gluteal muscles?
- The general action of these muscles is to laterally (externally) rotate the lower limb.
- They also stabilise the hip joint by ‘pulling’ the femoral head into the acetabulum of the pelvis.
Which muscle is a key landmark of the gluteal region and why?
piriformis because the sciatic nerve emerges from the
pelvis inferior to it
Describe the position of the piriformis
• most proximal member of the ‘deep muscles’
• Piriformis originates from the anterior surface of the
sacrum. It travels inferolaterally, through the greater sciatic foramen, to insert into the superior aspect of the greater trochanter of the femur.
What are the actions of the piriformis?
Lateral (external) rotation and abduction of the lower limb
What is the piriformis innervated by?
Nerve to piriformis (root values outside the scope of the MSK unit)
Describe the position of the obturator internus
- The obturator internus muscle forms part of the lateral wall of the pelvic cavity.
- It originates from the medial surface of the obturator membrane (which fills the obturator foramen) and from the adjacent pubis and ischium, travels through the lesser sciatic foramen, and inserts on the posterior aspect of the greater trochanter below the insertion of the piriformis and superior gemellus muscles.
What are the actions of the obturator internus?
Lateral (external) rotation and abduction of the lower limb.
What is the obturator internus innervated by?
Nerve to obturator internus (root values outside the scope of the MSK unit).
Describe the position of the Superior and Inferior Gemelli
- The gemelli are two narrow triangular muscles.
- They are separated by the obturator internus tendon
- The superior gemellus muscle originates from the ischial spine;
- the inferior gemellus originates from the ischial tuberosity.
- They insert on the posterior aspect of the greater trochanter of the femur, above and below the insertion of obturator internus respectively.
What are the actions of the Superior and Inferior Gemelli?
Lateral (external) rotation and abduction of the lower limb
What is the Superior and Inferior Gemelli innervated by?
superior gemellus muscle is innervated by the nerve to obturator internus, the inferior gemellus is innervated by the nerve to quadratus femoris.
Describe the position of the Quadratus Femoris
- The quadratus femoris is a flat, square-shaped muscle. • It is the most inferior of the deep gluteal muscles
- It originates from the lateral aspect of the ischial tuberosity and inserts onto the quadrate tubercle (located on the intertrochanteric crest, immediately inferior to the insertion of the inferior gemellus onto the greater trochanter)
What are the actions of the Quadratus Femoris?
Lateral (external) rotation of the thigh.
What is the Quadratus Femoris innervated by?
Nerve to quadratus femoris (root values outside of the scope of the MSK unit)
Describe the position of the Obturator externus
- it is sometimes classed as a member of the deep muscles of the gluteal region and sometimes as part of the medial compartment of the thigh.
- Obturator externus originates from external surface of obturator membrane (a membrane that occupies the obturator foramen), and from the adjacent bone.
- It passes posterior to the neck of femur, inserting onto the posterior aspect of the greater trochanter
What are the actions of the Obturator externus?
Adduction and lateral (external) rotation of the thigh.
What is the Obturator externus innervated by?
Obturator nerve (L2-L4)
What are the muscles in the posterior compartment of the thigh are collectively known as?
hamstrings
What doe the muscles in the posterior compartment of the thigh(hamstrings) consist of?
biceps femoris, semitendinosus and semimembranosus muscles, which form prominent tendons medially and laterally at the back of the knee
What is the function of the muscles of the posterior thing and what are they innervated by?
• act to extend the lower limb at the hip and flex it at the
knee.
• They are innervated by the tibial part of the sciatic nerve (except the short head of biceps femoris which is innervated by the common peroneal part of the sciatic nerve)
Describe the Biceps Femoris
• the biceps femoris muscle has two heads:
a long head and a short head.
• The common tendon of the two heads can be palpated laterally at the posterior knee.
• The long head of biceps femoris originates from the ischial tuberosity of the pelvis.
• The short head originates from the linea aspera on posterior surface of the femur.
• The two heads form a common tendon which inserts into the head of the fibula.
What are the actions of the Biceps Femoris?
The main action of biceps femoris is to flex the knee. It also extends the thigh at the hip, and laterally (externally) rotates the hip and knee
What is the Biceps Femoris innervated by?
The long head is innervated by the tibial part of the sciatic nerve, whereas the short head is innervated by the common peroneal (common fibular) part of the sciatic nerve
Describe the Semitendinosus muscle
- a largely tendinous muscle.
- It is sited medial to the biceps femoris and superficial to the semimembranosus muscles.
- Semitendinosus originates from the ischial tuberosity and inserts on the upper medial aspect of the tibia as part of the pes anserinus (Latin = goose’s foot)
What are the actions of the Semitendinosus muscle?
Semitendinosus flexes the leg at the knee joint. It also extends the thigh at the hip, medially (internally) rotates the thigh at the hip joint and medially (internally) rotates the leg at the knee joint.
What is the Semitendinosus muscle innervated by?
Tibial part of the sciatic nerve.
Describe the Semimembranosus muscle, including origin and insertion
- has a flat broad tendon of origin.
- It is located deep to the semitendinosus muscle.
- Attachments: Semimembranosus originates from the ischial tuberosity and inserts onto the medial tibial condyle.
- It does not form part of the pes anserinus.
What are the actions of the Semimembranosus muscle?
Semimembranosus flexes the leg at the knee joint. It also extends the thigh at the hip, medially (internally) rotates the thigh at the hip joint and medially (internally) rotates the leg at the knee joint. Its actions are therefore the same as those of semitendinosus
What is the Semimembranosus muscle innervated by?
Tibial part of the sciatic nerve.
What causes Hamstring injury “Pulled hamstring”?
•A pulled hamstring tends to occur during sudden muscular exertion that results in stretching of the posterior thigh muscles e.g. jumping, sprinting and lunging.
•It is relatively common in footballers and athletes, especially if proper warm-up exercises have not been performed beforehand.
•Sudden tension on the hamstrings results in either a muscle sprain, a partial tear or a complete tear of the origin of the hamstring muscles from the ischial tuberosity, sometimes
accompanied by avulsion of a fragment of bone.
What does the rectus femoris do?
- One of the 4 quadriceps muscles
- Only one to actually cross the hip joint (flexes the hip)
- Also crosses the knee joint (acts as a knee extender)
- supplied by femoral nerve
What does the satorius do?
- crosses both the hip and the knee
- synergist muscle
- hip flexion
- supplied by femoral nerve
What does the pectineus do?
- hip flexor but also adducts thigh
- supplied by femoral nerve
What is the gracilis?
- thin medial thigh muscle
- can be used in reconstructive surgery
- inserts into pes anserinus
nerve supply = obturator nerve
