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.
Posturally, the long head of the biceps femoris, along with the other hamstring muscles and the gluteus maximus, maintains posterior pelvic tilt. These muscles must be in balanced tension with the hip flexors to maintain a neutral pelvis. Excessive tension in the hamstring group may contribute to excessive posterior pelvic tilt, while weakness may result in excessive anterior tilt.
The short head of the biceps femoris joins the rest of the hamstring group in flexing the knee. This is a critical component of gait, particularly in shortening the lower limb during the swing-through phase.
The biceps femoris is also responsible for external rotation of the knee. Rotation at the knee is possible only when the knee is slightly flexed. Full extension locks the tibiofemoral joint and prevents rotation. Rotation on a flexed knee is used to change the direction of movement in the lower body when the foot is in contact with the ground. This “plant and pivot” movement is critical in sports such as basketball, football, soccer, and tennis, and is a common mechanism of injury during sports and activities of daily living.

Client Homework:
Hip Hinging
1. Stand with your feet shoulder-width apart.
2. Keeping your spine straight and knees slightly bent, shift your weight to your heels.
3. Push your hips back and bend forward at your hips to a 45-degree angle.
4. Lift your torso as you maintain a straight spine and press through your heels to engage the hamstrings and glutes.
Editor’s note: The Client Homework element in Functional Anatomy is intended as a take-home resource for clients experiencing issues with the profiled muscle. The stretches identified in Functional Anatomy should not be performed within massage sessions or progressed by massage therapists, in order to comply with state laws and maintain scope of practice.

Christy Cael is a licensed massage therapist and certified strength and conditioning specialist. Her private practice focuses on injury treatment, biomechanical analysis, craniosacral therapy, and massage for clients with neurological issues. She is the author of Functional Anatomy: Musculoskeletal Anatomy, Kinesiology, and Palpation for Manual Therapists (Lippincott Williams & Wilkins, 2009). Contact her at functionalbook@hotmail.com.