Semitendinosus (Hamstring)
Thigh · Lower Limb
The semitendinosus is a medial hamstring muscle, named for its long, cord-like tendon that occupies the lower half of the muscle. It arises from the ischial tuberosity and inserts on the superomedial surface of the tibia as part of the pes anserinus. It flexes the knee, extends the hip, and medially rotates the flexed knee. It is supplied by the tibial division of the sciatic nerve (L5, S1, S2).
Origin, Insertion, Action & Nerve
Origin
Ischial tuberosity
Insertion
Superomedial surface of tibia (pes anserinus)
Action
Flexion of knee; extension of hip; medial rotation of flexed knee
Nerve
Tibial division of sciatic nerve (L5, S1, S2)
Attachments explained
The Semitendinosus (Hamstring) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Ischial tuberosity
Insertion
Superomedial surface of tibia (pes anserinus)
Action & function
When the Semitendinosus (Hamstring) contracts, it produces the following movements: Flexion of knee; extension of hip; medial rotation of flexed knee.
As part of the Thigh group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Semitendinosus (Hamstring) receives its nerve supply from the Tibial division of sciatic nerve (L5, S1, S2). This nerve carries fibres from spinal segment(s) L5, S1, S2.
Because a muscle can only contract when its nerve is intact, injury to the Tibial division of sciatic nerve or to its spinal roots (L5, S1, S2) can weaken or paralyse the Semitendinosus (Hamstring), impairing the movements it normally produces (flexion of knee). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Semitendinosus (Hamstring) (the OIANS method)
Study the semitendinosus as the more superficial medial hamstring with the prominent tendon you can feel behind the medial knee. Because it arises from the ischial tuberosity and reaches the medial tibia, it extends the hip and flexes the knee like the whole group, but its medial insertion lets it rotate the flexed knee inward, opposite to biceps femoris.
Group it with sartorius and gracilis at the pes anserinus, and with the other true hamstrings on the tibial division of the sciatic nerve (L5, S1, S2). Pair it closely with semimembranosus, which lies deep to it and shares the same actions, so learning the two medial hamstrings together is efficient.
Frequently asked questions
Where is the Semitendinosus (Hamstring) located?
The Semitendinosus (Hamstring) is a muscle of the Thigh group, located in the Lower Limb.
What is the origin of the Semitendinosus (Hamstring)?
Ischial tuberosity
What is the insertion of the Semitendinosus (Hamstring)?
Superomedial surface of tibia (pes anserinus)
What movements does the Semitendinosus (Hamstring) produce?
Flexion of knee; extension of hip; medial rotation of flexed knee
What nerve supplies the Semitendinosus (Hamstring)?
Tibial division of sciatic nerve (L5, S1, S2)
Is the Semitendinosus (Hamstring) free to study in OIANS?
The Semitendinosus (Hamstring) is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Lower Limb is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
Study the Semitendinosus (Hamstring)
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