Muscles of Posterior Compartment of the Thigh PDF

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Summary

Muscles of the posterior compartment of the thigh - origin, insertion, innervation and action...

Description

ABCP2 anatomy of the lower limb MUSCLES OF POSTERIOR COMPARTMENT OF THE THIGH: THE HAMSTRINGS HAMSTRING MUSCLE

ORIGIN

INSERTION

BICEPS FEMORIS

Ischial tuberosity

Fibula=> lateral side of head of fibula

Most lateral hamstring

INNERVATION

ACTION Extend thigh at hip (e.g. when starting to walk) Flex leg at knee *both actions cannot be performed maximally => if knee flexed, hip extension weakened

SEMITENDINOSUS

Ischial tuberosity

Intermediate hamstring, superficial to semimembranosus

Tibia=> Medial proximal tibia aka Pes Anserinus (goose’s foot)

“the semiTendinosus is on Top of semimembranosus”

When knee flexed, SM & ST can medially rotate knee, BF can laterally rotate knee

SCIATIC NERVE (L4 -S3) Tibial division (L5, S1, S2)

Hamstrings keep us upright=> if paralysed tend to fall forward When walking on flat ground, H’s decelerate hip flexion at end of forward swing of the limb Important for acceleration in sprinting

SEMIMEMBRANOSUS Most medial hamstring & in some parts deep to semitendinosus

Ischial tuberosity

Tibia=> posterior part of medial condyle of tibia

Important for positioning of pelvis => if pelvis tilted anteriorly due to shortened quadriceps (often from excessive sitting) the hamstrings will feel tight (long, taut & weakened) & restrict hip flexion => so when bending forward (hip flexion on standing), the person will resort to excessive lumbar spine flexion (☹) to compensate for reduced hip flexion

**NOTE: Biceps Femoris SHORT HEAD = NON-HAMSTRING MUSCLE:    

Origin= linea aspera & lateral supracondylar lines of femur Insertion= fibula Innervation= sciatic nerve, common fibular division (L5, S1, S2) Action= flexion of leg at knee

** NOTE: the hamstring/ischiocondylar part of ADDUCTOR MAGNUS (of MC of Thigh) also considered a hamstring due to its attachment (origin) on ischial tuberosity, its sciatic nerve (tibial branch) innervation & its action in extending the thigh at hip joint...