Biceps Femoris – Anatomy Breakdown
Treadwell, DPT | Muscle by Muscle Series
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Watch on YouTube: Biceps Femoris – Anatomy Breakdown
In this episode, Dr. Austin Treadwell, DPT breaks down the Biceps Femoris — the lateral head of the hamstring trio and a powerhouse for hip extension, sprint speed, and posterior chain stability.
We’ll cover its anatomy, function, and why it’s one of the most commonly injured muscles in sport.
Overview
The Biceps Femoris has two heads — long and short — working together to extend the hip, flex the knee, and control rotation of the lower limb.
It’s the most lateral of the hamstring group, giving structure to the posterior thigh and anchoring dynamic control during sprinting, cutting, and deceleration.
Clinically, it’s one of the most frequently strained muscles in athletics — but also one of the most rehab-responsive when you understand its biomechanics.
Origin & Insertion
Long Head: Ischial tuberosity (with semitendinosus)
Short Head: Linea aspera and lateral supracondylar line of the femur
Insertion: Head of the fibula and lateral condyle of the tibia
Because of its dual origins, the Biceps Femoris spans both hip and knee joints — making it especially prone to strain during simultaneous hip flexion and knee extension (like in sprinting or kicking).
Function
Long Head: Hip extension, knee flexion, and external rotation of the tibia when the knee is flexed
Short Head: Pure knee flexion (no hip action)
Both Heads: Assist in decelerating knee extension during gait and absorbing eccentric load in sprinting
MRI and EMG data show the Biceps Femoris long head activates most strongly during late swing phase — when the hamstrings lengthen eccentrically to decelerate the limb (Higashihara et al., 2024).
That’s also the moment most strains occur.
Innervation & Blood Supply
Innervation:
Long Head — Tibial division of sciatic nerve (L5–S2)
Short Head — Common fibular division of sciatic nerve (L5–S2)
Blood Supply: Perforating branches of the deep femoral artery
Clinical & Training Insights
Long head strains often occur at the proximal myotendinous junction near the ischial tuberosity.
Eccentric strengthening (like Nordic curls and razor curls) significantly reduces re-injury risk.
The short head is more active in knee-dominant exercises (like prone hamstring curls).
Train both hip- and knee-dominant patterns for balanced hamstring function and reduced asymmetry.
Clinical insight: Reinjury risk is highest when athletes regain strength but not fascicle length — eccentric training (Nordics, RDLs) restores both (Timmins et al., 2016).
Clinical Relevance
The Biceps Femoris is more than a mover — it’s a stabilizer and decelerator for the entire posterior chain.
Dysfunction here can contribute to pelvic rotation, ACL risk, and chronic low-back tension.
Addressing timing and coordination between the Biceps Femoris and gluteus maximus is key for both performance and pain prevention.
Take the Next Step
You’ve got the anatomy down — now put it into motion.
If you’re a clinician, let’s talk posterior-chain rehab and return-to-play protocols.
If you’re an athlete or lifter, let’s talk hamstring power and resilience.
And if you’re dealing with chronic tightness or recurring strains — this is where anatomy meets recovery.
𖤓 Watch more breakdowns on YouTube: Treadwell, DPT – Muscle by Muscle Series
𖤓 Book a Virtual Consultation: TreadwellDPT.com/appointments
𖤓 Download free PT tools & anatomy resources: TreadwellDPT.com/resources
Much more in store; even more to come.
Stay tuned, stay locked. Treadwell, DPT. 🚀
