Posterior compartment of the thigh. Dr. Heba Kalbouneh Associate Professor of Anatomy and Histology

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1 Posterior compartment of the thigh Dr. Heba Kalbouneh Associate Professor of Anatomy and Histology

2 Posterior compartment of the thigh 1-Muscles: Biceps femoris Semitendinosus Semimembranosus Adductor magnus (hamstring part or ischial part) Hamstring part of adductor magnus 2- Blood supply: Branches of profunda femoris artery 3- Nerve supply: Sciatic nerve Semimembranosus Semitendinosus Biceps femoris

3 The posterior thigh muscles were called hamstrings because butchers used to hang pigs by these muscles outside their shops In ancient times, the soldiers utilized to slash the rear of the knees of horses of their rivals to be able to cut the tendons of hamstring muscles, to bring the horse and its rider down. They also utilized to cut the hamstring tendons of soldiers in order that they couldn t run. This was referred to as hamstringing the enemy.

4 Origin: All from ischial tuberosity EXCEPT Short head of biceps femoris from linea aspera and lateral supracondylar ridge. Insertion : Biceps femoris: head of fibula Semitendinosus: upper part of medial surface of the tibia (SGS). Semimembranosus: medial condyle of the tibia Adductor Magnus (Ischial head): Adductor tubercle of femur Ischial tuberosity Biceps femoris Long head All Extend the hip EXCEPT short head of biceps All Flex the knee EXCEPT adductor magnus Lateral muscles rotate the knee laterally Medial muscles rotate the knee medially Biceps femoris Short head

5 Biceps femoris Origin: two heads 1-Long head: ischial tuberosity 2-Short head: linea aspera, lateral supracondylar ridge Insertion: Head of fibula Nerve supply: Long head: tibial portion of sciatic nerve Short head: common fibular portion of sciatic nerve Action: Flexes and laterally rotates leg at knee joint; long head also extends thigh at hip joint

6 Semitendinosus Origin: Ischial tuberosity Where? Insertion: Upper part of medial surface of shaft of tibia (SGS area) Nerve supply: Tibial portion of sciatic nerve Action: Flexes and medially rotates leg at knee joint; extends thigh at hip joint

7 Semimembranosus Origin: Ischial tuberosity, where? Insertion: Medial condyle of tibia (posterior surface) Groove for semimembranosus Nerve supply: Tibial portion of sciatic nerve Action: Flexes and medially rotates leg at knee joint; extends thigh at hip joint

8 Biceps femoris Posterior Anterior

9 Semitendinosus

10 Semimembranosus

11 Quadratus femoris Ischial tuberosity Divided by a transverse ridge into: An upper quadrangular and a lower triangular parts Inferior gemellus The upper quadrangular part is divided by an oblique ridge into: 1- Upper Lateral part for the attachment of semimembranousus 2- Lower Medial for the attachment of semitendinosus and long head of biceps Medial Lateral The lower triangular part is divided by a longitudinal ridge into: 1-Lateral part that gives attachment to the ischial part of the adductor magnus 2-Medial part (subcutaneous part) Covered by connective tissue and bursa When sitting, this medial part supports the body weight The ischial tuberosity is covered by gluteus maximus when one stands. In the sitting position the muscle slips away laterally. To palpate this bony point, therefore, feel for it uncovered by gluteus maximus in the flexed position of the hip

12 Pay attention to the fact that the muscles of the thigh are designed To act on the knee joint For example, quadriceps femoris occupies the anterior compartment of the thigh but its Main action is to extend the knee joint The same should be considered for the muscles of the posterior compartment of the thigh Although they occupy the posterior compartment of the thigh Their main function is to flex the knee joint Now think! Which muscles will rotate the knee joint medially and laterally? Keep in your mind that when the knee joint is extended medial and lateral rotation is not possible! The joint said to be locked Therefore, we need to unlock the extended (locked) knee joint A small muscle called popliteus unlocks the knee joint by rotating the femur on the tibia laterally before any flexion of the knee can take place Now the joint is unlocked Only now when the knee joint is semiflexed: The biceps femoris can act as a lateral rotator of the leg The semimembranousus and semitendinosus can act as medial rotators of the leg

13 Sciatic nerve A branch of the sacral plexus (L4 L5 S1 S2 S3) Emerges from the pelvis through the greater sciatic foramen below piriformis Is the largest nerve in the body Consists of the tibial and common fibular nerves bound together with fascia. Commonly terminates in the lower third of the thigh by dividing into: Tibial nerve (Medial popliteal nerve) Common fibular nerve (Lateral popliteal nerve or Common peroneal nerve)

14 PSIS Surface anatomy of sciatic nerve Greater trochanter Ischial tuberosity The greater trochanter of the femur can be felt about one hand s width inferior to the midpoint of the iliac crest The ischial tuberosity is palpable just above the gluteal fold

15 Posterior Cutaneous Nerve of the Thigh A branch of the sacral plexus S1,2,3 Enters the gluteal region through the lower part of the greater sciatic foramen below piriformis Supplies the skin over the back of thigh and upper part of the leg