Human Movement Science & Functional Anatomy of the:
Biceps Femoris (Lateral Hamstring)
by Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS
- Long Head: Distal part of the sacrotuberous ligament and posterior part of the tuberosity of the ischium.
- Short Head: Lateral lip of the linea aspera, proximal 2/3 of the supracondylar line, and lateral intermuscular septum.
- Insertion: The long head and short head of the biceps femoris share a common tendon that inserts on the lateral side of the head of the fibula, lateral condyle of the tibia, and deep fascia on the lateral side of the lower leg.
- Long Head: Tibial nerve; a branch of the sciatic nerve via the sacral plexus, originating from nerve roots S1, S2, and sometimes L5 or S3
- Short Head: Fibular nerve (peroneal nerve); a branch of the sciatic nerve via the sacral plexus, originating from nerve roots L5 – S2
- Hip: Extension and some lateral rotation
- Knee: Flexor and tibial external rotator
- Pelvis: Posterior tilt
- Sacrum: Counter nutation (extension) via the sacrotuberous ligament in conjunction with a posterior tilt.
- Knee: Flexion and tibial external rotation.
- Hip: Although the short head of the biceps femoris does not cross the hip, it may contribute to femoral (hip) internal rotation (relative tibial external rotation) in a closed chain.
- Long Head:
Much of the information above can be found in “Muscles: Testing and Function with Posture and Pain” by Kendall, McCreary, Provance, Rodgers, and Romani
Quick Kinesiology Lesson:
- The short head of the biceps femoris may contribute to femoral internal rotation, tibial external rotation, and approximation (compression) of the lateral compartment of the knee; which results in deflection of the knee inward during closed chain activities (“functional valgus”).
- This is a bit of a quandary, as the long head may contribute to external rotation of the femur and bowing-out of the knees during closed chain activities (“functional varus”). Should the long head and the short head of the biceps femoris be treated as two different muscles despite sharing a common tendon; could the separate neural innervation have been a clue all along?
- Stabilization: Hip, knee, and SI joint
- Long head: hip flexion, internal rotation and adduction & knee extension and internal rotation
- Short head: knee extension and internal rotation, and femoral external rotation.
- Synergists: The long head of the biceps femoris is the primary synergist for hip extension (gluteus maximus is the prime mover) and has a propensity to become synergistically dominant for an inhibited gluteus maximus.
- Both the short and long head work synergistically with the semimembranosus and semitendinosus to produce knee flexion. Again, both heads of the biceps femoris have a propensity toward over-activity and may become dominant during knee flexion resulting in ancillary external rotation.
- The most important synergistic relationship in relation to movement impairment: The biceps femoris along with the TFL/ITB/VL complex and lateral gastrocnemius comprise the functional group that laterally stabilizes & externally rotates the knee resulting in a synergistic pairing with TFL/VL/ITB complex and the lateral gastrocnemius. The distal attachment of the iliotibial band creates a fascial network that interconnects the patellar tendon, the lateral collateral ligament, the anterior tibiofibular ligament and the tendon of the biceps femoris.
- The biceps femoris may become synergistically dominant for an inhibited gluteus maximus. A sign of this during dynamic assessment such as; squats, single leg squats, or sit-to-stand, is the “knees caving-in,” an anterior pelvic tilt, an asymmetrical weight shift or “feet turn-out.” Clinical implications may include iliotibial band syndrome, hip impingement syndrome, lateral and/or anterior knee pain, pain at the proximal attachment, biceps femoris trigger points and or tendonitis.
- This muscle may be seen as the team leader in a group of muscles that may become synergistically dominant during extension. See “deep longitudinal subsystem” for more information.
- Sacrum: The biceps femoris plays a role in stabilization of the sacrum, optimal alignment of the sacroiliac joint, and optimal arthrokinematics. The biceps femoris via fascial slips runs nearly continuous with the sacrotuberous ligament, and when the biceps femoris contracts this force is transmitted through the sacrotuberous ligament leading to counter-nutation (extension, or “tucking under”) of the sacrum in conjunction with posterior pelvic tilt on the ipsilateral innominate. However, it is important to note that when the biceps femoris contracts unilaterally, the result is counter-nutation and a posterior pelvic tilt on the ipsilateral side, but relative nutation and anterior tilting of the contralateral innominate. The biceps femoris is often overactive in individuals with SI joint dysfunction.
- Hip: In relation to hip mechanics very little is written in regard to arthrokinematics and the biceps femoris. It seems likely that the biceps femoris contributes to a superior glide of the femoral head in the acetabulum; however, it is probably more accurate to consider the affect the biceps femoris has on the pelvis and sacrum and the resultant position of the femoral head. For example a posterior pelvic tilt and sacral counter-nutation relative to a fixed femur would result in a relative anterior and superior shift of the femoral head.
- Knee: Although the biceps femoris may be thought of as a resistive force preventing an anterior glide of the femur and preventing ACL sprains, it can only act in this role if tonicity (activity) and length/tension are optimal. When overactive, the muscle can contribute to knee dysfunction by creating an adduction (valgus) force, external rotation of the tibia, and compression of the lateral compartment. The short head may contribute to an internal rotation moment of the femur reinforcing lower body pronation. It is probably easiest to visualize this action in closed-chain movement patterns (relative to a fixed tibia) – it may be helpful to imagine the short head of the biceps femoris as a “bow string” getting tighter and tighter, and the femur and tibia as the “bow” getting bent out of position.
- Proximal Tibiofibular Joint: When the knee is flexed the biceps femoris contributes to a posterior glide and external rotation of the proximal fibula on the tibia. This may serve to disrupt both knee and ankle mechanics (posterior glide of the proximal tib-fib joint results in an anterior glide of the distal tib-fib joint). Considering the dense network of structures that runs laterally from femoral condyle to fibular head, over-activity of the biceps femoris may contribute to LCL damage, fibular nerve impingement, patellar misalignment, damage to the lateral retinaculum, etc. Further, the anterior glide of the distal tib-fib joint may result in reduction in posterior talar glide and a reduction in dorsiflexion. This unto itself may result in various dysfunctions.
- Sacrotuberous Ligament – The long head of the biceps femoris runs nearly continuous with the sacrotuberous ligament transferring mechanical force to the sacrum and SI joint. Further the fascial connection from sacrotuberous ligament to lumbosacral fascia may hint at a synergistic relationship between the biceps femoris and lumbar extensors mediated by mechanoreceptors within this fascial sheath. Functionally, this appears to be the case, as those with an under-active gluteus maximus often rely on biceps femoris activity and an increase in lumbar extension to compensate during gate. It is my opinion, that this relationship is a solid rationale for adding the lumbar extensors to the deep longitudinal subsystem.
Iliotibial Band and Lateral Inter-muscular Septum – The iliotibial band (and lateral intermuscular septum which invests in to the ITB) creates a complicated network that invests in several structures:
- Lateral retinaculum and the patellar tendon
- The lateral collateral ligament at the knee
- Fibular head
- Anterior tibiofibular ligament
- Biceps femoris tendon
- The potential communicating synergies that may arise from this fascial network are staggering and could be the subject of an article unto themselves. To date, the most useful idea to arise from my personal consideration of this relationship has been the relationship between the iliotibial band and tibial external rotators. The iliotibial band may acts as a communicating medium for these muscle, contributing to over-activity in not one, but all of these structures. The external rotation force and posterior glide of the proximal fibular head also has significant implications in ankle mechanics.
- Hip Pain
- Knee Pain
- SIJ Pain
- Hip Impingement (FAI)
- Fibular Nerve Impingement
- Tendonitis at distal attachment of Biceps Femoris
- Hamstring Strains
- Iliotibial Band Syndrome
- Patellar femoral pain syndrome (PFPS)
- Trigger points in the posterior and lateral hip region.
Behavior in Postural Dysfunction:
This muscle should likely be treated as two different structures. While the short head of the biceps femoris has a tendency toward adaptive shortening and over-activity the long head has a tendency toward adaptive lengthening and over-activity. It should be mentioned that long head of the biceps femoris may become short and overactive on the dysfunctional side of SI joint dysfunction which often results in an asymmetrical Weight Shift. We find altered length and activity in lumbo pelvic hip complex dysfunction and lower leg dysfunction. For more information on these predictive models of dysfunction click on the link below:
In the models above we find the long head of the biceps femoris is adaptively lengthened when an individual adopts an anterior pelvic tilt (lower cross syndrome), but adaptively shortened on the dysfunctional side of SI joint dysfunction and/or an asymmetrical weight shift. Due to the propensity toward over-activity and adaptive lengthening (in most cases), the long head of the biceps femoris is generally released and not stretched (exercises below). If stretching techniques are utilized, active and dynamic stretching is preferred, as static stretching has the largest likelihood of increasing muscle length and may exacerbate postural dysfunction.
“Knees Bow In” Break Down:
“Feet Turn Out” Break Down:
“Anterior Pelvic Tilt” Break Down:
Signs of Altered Length/Tension and Tone:
- Asymmetrical Weight Shift: Both Heads – Short/Over-active on side of dysfunction
- Anterior Pelvic Tilt: Both heads – Long/Over-active on both sides
- Knees Bow In: Short Head – Long/Over-active on both sides
- Knees Bow Out: Long Head – Short/Over-active on both sides
- Feet Turn Out: Short Head – Short/Over-active on both sides
Single Leg Squat:
- Knee Bows In – Long/Over-active
- Knee Bows Out – Short/Over-active
- Goniometric Assessment
- Hip Internal Rotation: < 45°
- Hip Flexion/Knee Extension (90°/90°): > 20°
Palpation of the Biceps Femoris:
- Palpation results in tenderness (trigger points or tender points) and may result in radiating symptoms to the posterior knee.
Specific Techniques for the Biceps Femoris
Biceps Femoris SA Static Release:
Biceps Femoris SA Active Release:
Biceps Femoris Active Stretch:
Workshop Snippet: When Should We Stretch The Hamstrings?
- Phillip Page, Clare Frank, Robert Lardner, Assessment and Treatment of Muscle Imbalance: The Janda Approach © 2010 Benchmark Physical Therapy, Inc., Clare C. Frank, and Robert Lardner
- Dr. Mike Clark & Scott Lucette, “NASM Essentials of Corrective Exercise Training” © 2011 Lippincott Williams & Wilkins
- Donald A. Neumann, “Kinesiology of the Musculoskeletal System: Foundations of Rehabilitation – 2nd Edition” © 2012 Mosby, Inc.
- Michael A. Clark, Scott C. Lucett, NASM Essentials of Personal Training: 4th Edition, © 2011 Lippincott Williams and Wilkins
- Leon Chaitow, Muscle Energy Techniques: Third Edition, © Pearson Professional Limited 2007
- Tom Myers, Anatomy Trains: Second Edition. © Elsevier Limited 2009
- Shirley A Sahrmann, Diagnoses and Treatment of Movement Impairment Syndromes, © 2002 Mosby Inc.
- David G. Simons, Janet Travell, Lois S. Simons, Travell & Simmons’ Myofascial Pain and Dysfunction, The Trigger Point Manual, Volume 1. Upper Half of Body: Second Edition,© 1999 Williams and Wilkens
- Cynthia C. Norkin, D. Joyce White, Measurement of Joint Motion: A Guide to Goniometry – Third Edition. © 2003 by F.A. Davis Company
- Cynthia C. Norkin, Pamela K. Levangie, Joint Structure and Function: A Comprehensive Analysis: Fifth Edition © 2011 F.A. Davis Company
© 2013 Brent Brookbush
Questions, comments, and criticisms are welcome and encouraged.