Kinesiology

Lesson 14 of 16

Thigh muscles

The thigh contains large muscle groups that act at the hip, knee, or both. Quadriceps extend the knee, while hamstrings generally flex the knee and extend the hip. The adductor group has a major role in bringing the thigh toward midline. Functional actions depend on joint position and whether the limb is fixed or moving.

Key points

• Quadriceps femoris includes rectus femoris and three vasti; all extend the knee.
• Rectus femoris also flexes the hip because it crosses that joint.
• Hamstrings cross the posterior thigh; most extend hip and flex knee.
• Sartorius crosses both hip and knee and contributes to combined movements.
• Adductor magnus has portions with different actions and attachment patterns.
• Avoid deep pressure over sensitive neurovascular structures in the medial thigh.

Key terms

Rectus femoris

O: anterior inferior iliac spine and superior acetabular rim; I: patella and tibial tuberosity via patellar ligament; A: extends knee and flexes hip.

Vastus lateralis

O: greater trochanter and lateral linea aspera; I: patella and tibial tuberosity via patellar ligament; A: extends knee.

Vastus medialis

O: intertrochanteric line and medial linea aspera; I: patella and tibial tuberosity via patellar ligament; A: extends knee and supports patellar tracking.

Biceps femoris

O: ischial tuberosity (long head) and linea aspera (short head); I: head of fibula; A: flexes knee and laterally rotates flexed leg; long head extends hip.

Semitendinosus

O: ischial tuberosity; I: medial proximal tibia; A: extends hip, flexes knee, and medially rotates flexed leg.