Gluteal Region, Posterior Thigh and Leg

Question 1

Describe the Surface Anatomy of the Gluteal Region

Answer 1

• Gluteal region lies posterior to pelvis from level of iliac crests (L4) to the gluteal fold, which marks the inferior border of gluteus maximus
• The gluteal region is a common site for intramuscular injections. In order to avoid the sciatic nerve, the superolateral quadrant is considered a “safe zone” for injection

Question 2

What are the Superficial Gluteal Muscles?

Answer 2

• Gluteus maximus
• Gluteus medius and minimus
• Tensor fasciae latae

Question 3

Describe insertion, action, and innervation for the Gluteus maximus

Answer 3

• Insertion: iliotibial tract and gluteal tuberosity of femur
• Action: extend and laterally rotate hip joint (e.g., rising from sitting position, climbing stairs)
• Innervation: inferior gluteal nerve (L5-S2)

Question 4

Describe insertion, action, and innervation for the Gluteus medius and minimus

Answer 4

• Insertion: greater trochanter of femur
• Action: abduct and medially rotate hip joint; keep pelvis level when contralateral leg is raised
• Innervation: superior gluteal nerve (L5-S1)
• If the superior gluteal nerve is injured, when a person is asked to stand on that limb, the pelvis tilts towards the unsupported side (this is called a positive Trendelenburg test)
• So, injury to the right superior gluteal nerve will cause the pelvis to tilt on the left side

Question 5

Describe origin, insertion, action, and innervation for the Tensor fasciae latae

Answer 5

• Origin: ASIS
• Insertion: iliotibial tract
• Action: tense the fascia lata, thus improving efficiency of other thigh muscles and assisting venous return; weakly flex and medially rotate hip joint
• Innervation: superior gluteal nerve (L5-S1)

Question 6

What are the Deep Gluteal Muscles?

Answer 6

1) Piriformis
- Superior gluteal vessels/nerve emerge superior to it
- Inferior gluteal vessels/nerve emerge inferior to it
2) Obturator internus
3) Superior and inferior gemelli
4) Quadratus femoris

Note: Obturator externus (part of the medial compartment of the thigh, innervated by obturator nerve) also laterally rotates and stabilizes the hip joint

Question 7

Describe origin, action, and innervation for the Deep Gluteal Muscles

Answer 7

• Origin from pelvic girdle and insertion on the proximal femur
• Action rule: laterally rotate and stabilize the hip joint
• Innervation rule: small motor branches of the sacral plexus

Question 8

Describe the pathway (location) of the Sciatic nerve (L4-S3)

Answer 8

• Exits greater sciatic foramen inferior to piriformis
• Courses deep to gluteus maximus (but does NOT innervate gluteal muscles)
• Sciatic nerve really consists of two nerves: tibial n. (medial) and common fibular n. (lateral)
• The tibial and common fibular nerves usually separate in the distal thigh (e.g., just proximal to the popliteal fossa); however, this can vary (e.g., in ~12% of people, the two nerves separate as they leave the pelvis, with the common fibular nerve passing through piriformis)

Question 9

What can Excessive use of the deep gluteal muscles (e.g., in athletes such as ice skaters, cyclists, rock climbers) lead to?

Answer 9

-Can lead to hypertrophy or spasm of the piriformis muscle, which can compress the sciatic nerve (piriformis syndrome). In individuals with a proximal split of the sciatic nerve (~12%), the common fibular nerve can become compressed as it passes through piriformis.

Question 10

What are the muscles of the Posterior Compartment of the Thigh?

Answer 10

1) Hamstrings
- Semitendinosus (medial)
- Semimembranosus (medial, deep to semitendinosus)
- Long head of Biceps femoris (lateral)
2) Short head of Biceps femoris

Question 11

What are the origin, action, insertion and innervation of the Hamstring (with exceptions)

Answer 11

1) Hamstrings
- Origin rule: ischial tuberosity
- Action rule: extend hip joint and flex knee joint
- Innervation rule: tibial nerve (L5-S2) (part of sciatic n.)
2) Semitendinosus (medial)
- Insertion: proximal tibia
3) Semimembranosus (medial, deep to semitendinosus)
- Insertion: proximal tibia
4) Long head of Biceps femoris (lateral)
- Insertion: proximal fibula

Question 12

What are the origin, action, insertion, and innervation of the Short head of Biceps

Answer 12

• Short head of Biceps femoris is not a hamstring muscle
• Origin: linea aspera of femur
• Insertion: proximal fibula (via shared tendon with long head)
• Innervation: common fibular nerve (part of sciatic n.)
• Action: flex knee joint

Question 13

Describe the pes anserinus

Answer 13

• The tendons of semitendinosus, gracilis, and sartorius fuse distally to insert on the medial aspect of the proximal tibia, forming the pes anserinus, or “goose’s foot.”
• Irritation of the bursa underlying the pes anserinus (pes anserinus bursitis) can cause pain on the medial aspect of the knee.

Question 14

What are the muscles of the Lateral Compartment of the Leg

Answer 14

• Fibularis (peroneus) longus

- Fibularis (peroneus) brevis

Question 15

What is the GENERAL action, and innervation of the Lateral Compartment of the Leg

Answer 15

• Action rule: evert foot and weakly plantarflex ankle joint
• Innervation rule: superficial fibular nerve (L5-S2)
• Branch of the common fibular nerve
• Innervates the muscles of the lateral compartment of the leg
• Innervates the skin of anterolateral leg and most of the dorsal foot

Question 16

What are the insertions and actions for Fibularis (peroneus) longus and brevis?

Answer 16

1) Fibularis (peroneus) longus
- Insertion: tendon passes posterior to the lateral malleolus, crosses the sole of the foot, and inserts on the base of first metatarsal & medial cuneiform
- Actions: evert foot; weakly plantarflex ankle joint

2) Fibularis (peroneus) brevis
- Insertion: tendon passes posterior to the lateral malleolus to insert on tuberosity of the fifth metatarsal
- Actions: evert foot; weakly plantarflex ankle joint

Question 17

What happens if the common fibular nerve is injured where it wraps around the neck of the fibula?

Answer 17

• The muscles in the anterior and lateral compartments of the leg and the dorsal foot will be affected. The patient will present with foot drop, which is caused by a loss of dorsiflexion and toe extension.
• The foot may also be inverted, as eversion is also affected.
• Note: one invertor will be affected (tibialis anterior is innervated by the deep fibular nerve) but one invertor will still be intact (tibialis posterior is innervated by the tibial nerve).

Question 18

What are the muscles of the Posterior Compartment of the Leg

Answer 18

1) Superficial Group
- Gastrocnemius
- Soleus
- Plantaris
2) Deep Group
- Popliteus
- Flexor digitorum longus (FDL)
- Flexor hallucis longus (FHL)
- Tibialis posterior

Question 19

What are the origin, action, insertion and innervation of the Superficial Group (with exceptions)

Answer 19

1) Superficial Group
- Insertion: calcaneal tuberosity via calcaneal (Achilles) tendon
- Calcaneal tendon reflex tests the tibial nerve and the S1-S2 spinal levels (note: it primarily tests the S1 spinal level (lesion at this level will result in a virtually absent calcaneal reflex))
- Gastrocnemius + soleus = Triceps surae

2) Gastrocnemius (medial and lateral head)
- Actions: flex knee joint and plantarflex ankle joint

3) Soleus
- Action: plantarflex ankle joint

4) Plantaris (small muscle belly with a long, thin tendon)
- Note: absent in 5-10% of people
- Actions: weakly flex knee joint and plantarflex ankle joint

Question 20

What are the origin, action, insertion and innervation of the Deep Group (with exceptions)

Answer 20

1) Popliteus
- Action: unlocks the knee from extended position (when knee is extended in standing position, popliteus rotates the femur laterally 5 degrees on the tibia, unlocking the knee so that flexion can occur)

2) Flexor digitorum longus (FDL)
- Insertion: tendon travels posterior to medial malleolus of tibia in tarsal tunnel, divides into four tendons to insert on distal phalanges, digits 2-5
- Actions: flex digits 2-5 (MTP, PIP & DIP joints); plantarflex ankle joint

3) Flexor hallucis longus (FHL)
- Insertion: tendon travels posterior to medial malleolus of tibia in tarsal tunnel and inserts on distal phalanx of hallux
- Actions: flex hallux (MTP & IP joints); weakly plantarflex ankle joint

4) Tibialis posterior
- Insertion: tendon travels posterior to medial malleolus of tibia in tarsal tunnel and inserts primarily on the navicular tuberosity
- Actions: plantarflex ankle joint; invert foot

Question 21

Describe the flexor retinaculum and what runs through them

Answer 21

Tendons of flexor digitorum longus, flexor hallucis longus, and tibialis posterior are held in place in the tarsal tunnel by the flexor retinaculum, which forms the roof of the tarsal tunnel

Question 22

Explain “Tom, Dick, ANd Harry”

Answer 22

“Tom, Dick, ANd Harry” helps summarize the relative position (anterior, middle, & posterior) of the tendons of tibialis posterior (Tom), flexor digitorum longus (Dick), and flexor hallucis longus (Harry) as they travel posterior to the medial malleolus in the tarsal tunnel; the posterior tibial artery/vein and tibial nerve (and) lies between the tendons of FDL and FHL

Question 23

Describe the Vasculature in the Gluteal region

Answer 23

• Gluteal arteries arise from the internal iliac artery
  1) Superior gluteal artery
• Exits greater sciatic foramen superior to piriformis
  2) Inferior gluteal artery
• Exits greater sciatic foramen inferior to piriformis

Superior and inferior gluteal veins accompany the arteries and are tributaries of the internal iliac vein

Question 24

Describe the Vasculature in the Posterior thigh

Answer 24

• Perforating branches from the deep artery of the thigh (primary source) and obturator artery
• Deep vein of the thigh

Question 25

Describe the Vasculature in the Posterior and lateral leg

Answer 25

• Femoral artery passes through adductor hiatus and becomes the popliteal artery
• Branches of the popliteal artery
  1) Geniular branches (genu = knee)
  2) Anterior tibial artery
  3) Posterior tibial artery

Question 26

Describe the Geniular Branches of the popliteal artery

Answer 26

-Form anastomoses around the knee joint

Question 27

Describe the Anterior tibial artery of the popliteal artery

Answer 27

• Passes through gap in superior part of the interosseous membrane
• Supplies anterolateral leg and dorsal foot (see Anterior Thigh and Leg and Dorsal Foot lab)

Question 28

Describe the Posterior tibial artery of the popliteal artery

Answer 28

• Travels with tibial nerve, between superficial & deep muscle groups
• Supplies posterior leg
• Gives off fibular artery, which supplies posterolateral leg (including lateral compartment)
• Around the ankle, the posterior tibial artery gives off medial malleolar and calcaneal branches while the fibular artery gives off lateral malleolar and calcaneal branches (form anastomoses around ankle joint)
• Posterior tibial artery travels posterior to medial malleolus in the tarsal tunnel, between tendons of FDL and FHL (“Tom, Dick, And Harry”), deep to flexor retinaculum (can palpate the posterior tibial pulse here)

Question 29

Describe the Deep veins of the posterior and lateral leg

Answer 29

Deep veins of the posterior and lateral leg parallel the arteries and share the same names (popliteal v., anterior tibial vv., posterior tibial vv., fibular v.); recall that the popliteal vein also receives blood from the small saphenous vein (draining superficial tissues)