Biceps Femoris (Hamstring)
Thigh · Lower Limb
The biceps femoris is the lateral member of the hamstring group and, as its name suggests, has two heads. The long head arises from the ischial tuberosity, while the short head arises from the linea aspera and lateral supracondylar line of the femur; the two join to insert on the head of the fibula. It flexes the knee and laterally rotates the flexed knee, and the long head also extends the hip. Its innervation reflects its two heads: the long head is supplied by the tibial division of the sciatic nerve (L5, S1, S2) and the short head by the common fibular division (L5, S1, S2).
Origin, Insertion, Action & Nerve
Origin
Long head: ischial tuberosity; Short head: linea aspera and lateral supracondylar line of femur
Insertion
Head of fibula
Action
Flexion of knee; lateral rotation of flexed knee; long head extends hip
Nerve
Long head: tibial division of sciatic nerve (L5, S1, S2); Short head: common fibular division of sciatic nerve (L5, S1, S2)
Attachments explained
The Biceps Femoris (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
Long head: ischial tuberosity; Short head: linea aspera and lateral supracondylar line of femur
Insertion
Head of fibula
Action & function
When the Biceps Femoris (Hamstring) contracts, it produces the following movements: Flexion of knee; lateral rotation of flexed knee; long head extends hip.
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 Biceps Femoris (Hamstring) receives its nerve supply from the Long head: tibial division of sciatic nerve (L5, S1, S2); Short head: common fibular 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 Long head: tibial division of sciatic nerve or to its spinal roots (L5, S1, S2) can weaken or paralyse the Biceps Femoris (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 Biceps Femoris (Hamstring) (the OIANS method)
Learn the biceps femoris by its two heads, since the difference between them explains both its actions and its nerves. Only the long head crosses the hip from the ischial tuberosity, so only it extends the hip, while both heads meet at the fibular head to flex the knee. Its lateral insertion is what allows it to rotate the flexed knee outward, unlike the medially inserting hamstrings.
Fix the split nerve supply as the muscle's signature: the long head is on the tibial division and the short head on the common fibular division of the sciatic nerve (both L5, S1, S2). Contrast this lateral hamstring, which laterally rotates the knee, with semitendinosus and semimembranosus, which rotate it medially, to keep the group straight.
Frequently asked questions
Where is the Biceps Femoris (Hamstring) located?
The Biceps Femoris (Hamstring) is a muscle of the Thigh group, located in the Lower Limb.
What is the origin of the Biceps Femoris (Hamstring)?
Long head: ischial tuberosity; Short head: linea aspera and lateral supracondylar line of femur
What is the insertion of the Biceps Femoris (Hamstring)?
Head of fibula
What movements does the Biceps Femoris (Hamstring) produce?
Flexion of knee; lateral rotation of flexed knee; long head extends hip
What nerve supplies the Biceps Femoris (Hamstring)?
Long head: tibial division of sciatic nerve (L5, S1, S2); Short head: common fibular division of sciatic nerve (L5, S1, S2)
Is the Biceps Femoris (Hamstring) free to study in OIANS?
The Biceps Femoris (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.
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Study the Biceps Femoris (Hamstring)
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