Posterior Thigh Flashcards
Describe the characteristics of hamstring muscles:
Attachment: Ischial tuberosity
Innervation: Sciatic (tibial division)
Action: Extend Hip & Flex knee
Describe the semitendinosus
Originates from ischial tuberosity
Inserts into the pes anserinus - tendon on medial side of the tibia
Function - knee flexion, hip extension, medial rotation
Innervated by the tibial division of the sciatic nerve (L5, S1, S2)
Blood supply - deep femoral artery + popliteal artery
Located medial to the biceps femoris and lateral to the semimembranosus.
Describe the semimembranosus
Originates from the ischial tuberosity
Inserts into the posterior part of the medial condyle of the tibia
Function - knee flexion, hip extension, medial rotation
Innervated by the tibial division of the sciatic nerve (L5, S1, S2)
Most medial muscle of the hamstring group
Describe the Biceps Femoris - long head
Originates from the ischial tuberosity of the pelvis
Inserts into the head of the fibula
Fusiform muscle
Innervated by the tibial division of the sciatic nerve (L5, S1, S2)
Blood supply - deep femoral artery + popliteal artery
Function - knee flexion + hip extension
Long head lies superficial to the short head
Situated laterally to other hamstring muscles
Sends some tendinous fibers to the lateral tibial condyle via the tibial collateral ligament.
Describe the sciatic nerve
Largest nerve in body (really it is 2 nerves in 1 sheath)
From L4 – S3 anterior rami
Enters gluteal region via Greater sciatic notch
Runs deep to biceps femoris
Enters Popliteal fossa
Divides into Tibial & Common fibular nerves
Describe the anatomy popliteal fossa:
Diamond shaped space posterior to knee
Borders;
Biceps femoris - superolaterally
Semitendinosus & Semimembranosus (superomedially)
Medial & Lateral heads of gastrocnemius (inferiorly)
Roof - Popliteal fascia, skin
Floor - Femur, Popliteus muscle
What are the contents of the popliteal fossa?
Popliteal artery and vein
Tibial nerve - runs medially
Common fibular nerve - Winds around the neck of the fibula and is more superficial and lateral
Small saphenous vein - draining to popliteal vein
Fat and lymph nodes
Popliteus muscle - originates from the lateral condyle of the femur and inserts into the posterior surface of the tibia
Describe the biceps femoris - short head:
Originates from the linea aspera on the posterior surface of the femur
Inserts into the head of the fibula, lateral to the long head of the biceps femoris
Function - knee flexion
Innervated by the common fibular (peroneal) division of the sciatic nerve (L5, S1, S2)
Blood supply - deep femoral artery + popliteal artery
What is the relationship between the Sartorius, Gracilis and Semitendinosus
Common insertion point - pes anserinus on the medial side of the tibia
Functional synergy - The action of the sartorius and gracilis in flexing and rotating the knee complements the function of the semitendinosus in flexing the knee and extending the hip, allowing for coordinated lower limb movements
Describe the tibial division of the sciatic nerve
Motor innervation of the hamstring muscles (except for the short head of the biceps femoris), and muscles of the posterior compartment of the leg
Formed from the anterior divisions of the L4 to S3 nerve roots
Continues down the back of the thigh, passing behind the knee to enter the popliteal fossa.
Branches into;
Medial Plantar Nerve - medial aspect of the foot.
Lateral Plantar Nerve - lateral aspect of the foot
Medial Sural Cutaneous Nerve - provides sensory innervation to part of the lower leg.
Describe the common fibular division of the sciatic nerve
Motor innervation to the muscles of the lateral and anterior compartments of the leg
Formed from the posterior divisions of the L4 to S2 nerve roots
Wraps around the neck of the fibula
Branches into;
Superficial fibular nerve - lateral leg and dorsum of foot
Deep fibular nerve - anterior part of leg
Describe a typical hamstring tear:
Often occurs near proximal attachment - ischial tuberosity
Caused by explosive contraction or stretching (flexion of hip when knee is extended)
Avulsion - complete tear where the tendon or part of ischial tuberosity separates from pelvis
What is sciatica?
Pain felt radiating along the course of the sciatic nerve
Caused by;
Intervertebral disc is bulging and compressing any of L4-S3 nerve roots
Compression by piriformis due to spasm or variation in exit of sciatic n
What are the 3 types of muscular contraction?
Concentric - Muscle contracts & shortens
Isometric - Muscle contracts (increase in tone)
but length does not change
Eccentric - Muscle contracted & lengthens
Describe antagonists, agonists and synergists:
Antagonists - slowly relaxes as agonist contracts, would usually
produce opposing movement
Agonists - muscles causing the movement by contracting
Synergists - contract at same time as agonist
