Issue link: https://www.massageandbodyworkdigital.com/i/398416
F r e e m u s i c d o w n l o a d s f o r C e r t i f i e d m e m b e r s : w w w. a b m p . c o m / g o / c e r t i f i e d c e n t r a l 47 FUNCTIONAL ANATOMY education Biceps Femoris By Christy Cael The biceps femoris is located on the posterior thigh and is one of three muscles that form the hamstring group. Of the three hamstring muscles, it is the most lateral and has two distinct heads. The long head of the biceps femoris spans the entire thigh and crosses both the hip and the knee. It originates from a common tendon with the other hamstring muscles—the semimembranosus and semitendinosus—on the ischial tuberosity. This common origin lies deep to the gluteus maximus, but is still palpable when clients are positioned prone with a slightly flexed knee. Moving distally from the common origin, the long head of the biceps femoris runs laterally down the posterior thigh, while the semimembranosus and semitendinosus muscles run medially. The fusiform fibers of the long head of the biceps femoris end in a broad aponeurosis where the long and short heads join. The short head originates between the adductor magnus and vastus lateralis on the lateral lip of the linea aspera. A common tendon is formed distally by the long and short heads of the biceps femoris and is located superficially on the posterolateral knee. This tendon forms the superolateral border of the popliteal fossa, then inserts on the head of the fibula and lateral condyle of the tibia. Functionally, the long head of the biceps femoris works with the semimembranosus, the semitendinosus, and the gluteus maximus to extend the hip. The gluteus maximus dominates when the knee is flexed, such as when standing up from a seated position. The three hamstring muscles play a bigger role when the knee is near full extension, helping to power movements like jumping and sprinting. They are also very active in pulling the torso upright from a bent position. This "hip hinging" motion is used when lifting items out of the trunk of a car or when bending at the waist to reach over an obstacle. The hamstrings and gluteus maximus are activated eccentrically to control the forward bending movement and concentrically to pull the pelvis back over the femurs. BICEPS FEMORIS Attachments • Origin: Ischial tuberosity (long head), lateral lip of linea aspera (short head) • Insertion: Head of fibula and lateral condyle of tibia Actions • Extends and externally rotates the hip • Flexes the knee • Externally rotates the flexed knee Innervation • Sciatic nerve • L5–S3